Tormek Community

In the Shop => Knife Sharpening => Topic started by: wootz on August 02, 2015, 02:14:37 pm

Title: Long Knife Jig asymmetry problem
Post by: wootz on August 02, 2015, 02:14:37 pm
Recently started using the Long Knife Jig SVM-140, and noticed that bevel on one side gets always wider than on the other.
Trying to understand what's happening, having turned it over to the second side checked the angle again with the AngleMaster, and was surprised to see the angle is not the same.
The problem is with both kitchen knives and thicker hunting ones.
Now to obtain the same bevel on both sides, I have to adjust the angle every time I flip over the jig.

The only explanation I have is the way they manufacture the jig does not center the clamp right.
Have never had this issue with the regular Knife Jig SVM-45.

Has anyone had similar problem? My jig is of newer design (without locking screw on the stop).
Am thinking of grinding inner surface of one of the clamps to compensate for the asymmetry, but decided to check with you guys first.
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on August 02, 2015, 02:36:36 pm
Welcome to the forum, Wootz.

The Tormek factory in Sweden is presently closed for the annual holiday time. Tormek will be back on the fourth. Tech support should have an answer for you. (support.tormek.se is the email address) Stig often checks the forum. He will be back on the fourth.

I suggest you do not grind down your jig until we hear from Sweden.

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: wootz on August 02, 2015, 02:50:54 pm
Thank you, Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on August 02, 2015, 04:06:53 pm
Let us know what you find out.

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: wootz on August 02, 2015, 11:18:10 pm
I found out that... the stone was out of true.  :-[
The stone was slightly conical, causing the change in angle on flipping over the blade.
Truing the stone has eliminated that.

Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on August 03, 2015, 01:23:31 am
Excellent, Wootz! New knowledge is always welcome. Thanks for sharing and keep posting.

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: Elden on August 04, 2015, 07:15:47 am
Welcome to the forum, Vadim.

    In a previous thread, there was some discussion concerning uneven bevel angles resulting from the design of the knife jigs. One side of the jig is fixed while the other side is a movable jaw. 
   Theoretically therefore, only one certain knife thickness will achieve an equal bevel angle on each side when ground. On thinner knives, a shim could be used to center the knife in the jig. Thicker knives will have a greater difference in the side to side bevel angles. It was pointed out, that the knife could be turned over in the jig in order to achieve the same bevel angles.
   I suppose that the field of invention is open to a jig that would center the knife to its centerline.
Title: Re: Long Knife Jig asymmetry problem
Post by: Stickan on August 04, 2015, 10:11:43 am
Hi,
On regular chef knifes or blades where the back is no more than 3-4 mm its extremely little difference in the edge-line. The knife jigs are designed to fit the most common knife models. We have several knife-sharpening business companies who uses our jigs and even several knife resellers and brands who recommends us for sharpening their knifes.
On more powerful knifes, like a hunting knife with a wider back you can see the difference more. So than you need to mark both sides.
A thing that almost never comes up in a discussion like this is than many knifes don't have the  the edge centred in the blade. It´s pretty easy to see, before you start sharpening a knife, hold the knife with the tip upwards and check if the edge-line is the same on both sides, you will be surprised how many knifes that are off-centred, and many times it´s the more expensive hand made knifes.

The jigs are designed to sharpen the most common sizes, some knifes you need to find and learn the technique so you get a "fabric" edge line.

Best,
Stig.
Title: Re: Long Knife Jig asymmetry problem
Post by: wootz on August 04, 2015, 12:49:28 pm
kb0rvo, your post is my gut feeling explained in plain and precise terms.
With the next hunting knife I'll definitely try marking position of the clamp on the blade, and turning over the blade in the jig rather than the jig itself. And if it delivers better result, for collectible knives I can put up with the inconvenience.

Such a clever and responsive forum, pure pleasure to look in.
Title: Re: Long Knife Jig asymmetry problem
Post by: Stickan on August 04, 2015, 01:20:05 pm
Wootz,
Please check if the edge is actually in the middle of the blade aslo!

Best ,
Stig
Title: Re: Long Knife Jig asymmetry problem
Post by: wootz on August 27, 2015, 09:39:09 am
Wootz,
Please check if the edge is actually in the middle of the blade aslo!

Best ,
Stig

Sure, it factors as well.
Presuming the bevel mirrors as you turn over the knife jig was wrong for all the above reasons.
Now, with thicker knives, as I turn over the jig, I mark the bevel and use the jig adjustable stop to equal the grinding angle with the other side, normally the needed adjustment is within half a turn.

Thanks again, guys, for your hints.
Title: Re: Long Knife Jig asymmetry problem
Post by: wootz on November 04, 2015, 04:43:26 am
I realized the problem with adjustments every time as the knife is flipped over, is that when I have to alternate sides, it is impossible to maintain strictly the same angle, and because of that I cannot get sharp edge.

I ended up by buying a second knife jig, and filing away 1 mm from the static clamp.
Now I have a dedicated jig for knives 3mm and over thick.
Not that I recommend this to everyone, but if you sharpen many thick knives, this helps to minimize the bevel asymmetry.

(http://home.exetel.com.au/dropbox/clamp.JPG)
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on November 04, 2015, 11:29:27 am
Well done, Wootz!

I agree, Elden, this field is very open for invention. Here is an idea which occured to me this morning:

Imagine a machine shop (or woodshop) V block which holds a round work piece in place to be accurately measured, cross drilled or sawn square. Now, imagine that V block being replaced with a simple home shop made  wooden cradle designed to hold a Tormek knife jig parallel to the flat surface (like the saw or drill press table).

With the knife clamped in the jig, and the jig setting in the cradle, slide a piece of wood with a parallel line scribed next to the edge of the knife. Ideally, the sharp edge of the knife should be the same height as the scribed line. Flip the knife and jig over and check the other side with the scribed line. If the knife is symmetrical, both sides should be the same height compared with the scribed line.

The height of the scribed line could be shimmed with paper or cardboard for different knife thicknesses. Shims could also be used to reposition the knife to make it symmetrical in the jig.

While this might seem like overkill, the extra care would be appreciated with collectible knives and fine kitchen cutlery.

The "table" could be a flat piece of MDF, wood or (my choice) baltic birch plywood. The cradle could be loose or secured to the table. It could be sized to be portable for mobile sharpeners.

Ken

Title: Re: Long Knife Jig asymmetry problem
Post by: Jimmy R Jørgensen on November 04, 2015, 12:37:10 pm
(http://i.imgur.com/BqOxi4Gm.jpg)
Title: Re: Long Knife Jig asymmetry problem
Post by: Jan on November 04, 2015, 01:17:09 pm
I realized the problem with adjustments every time as the knife is flipped over, is that when I have to alternate sides, it is impossible to maintain strictly the same angle, and because of that I cannot get sharp edge.

I ended up by buying a second knife jig, and filing away 1 mm from the static clamp.
Now I have a dedicated jig for knives 3mm and over thick.
Not that I recommend this to everyone, but if you sharpen many thick knives, this helps to minimize the bevel asymmetry.


Thank you, Wootz, for sharing with us your courageous solution.  :)

Important is, whether it really eliminates the bevel asymmetry. I am wondering, if the asymmetry is fully eliminated or rather reduced.

Recently, for some geometrical considerations, I prepared a sketch of the knife jig. I concluded that the knife jig is working fully symmetrically for knives which blades are not thicker than about 2 mm.

So, to modify the knife jig for 3 mm thick blades, for maintaining symmetry with respect to flipping, I would remove 0.5 mm from each clamp.

To modify the jig for 4 mm thick blades, I would remove 1 mm from each clamp.

Jan

(http://img15.rajce.idnes.cz/d1503/11/11662/11662961_154b127859a75fd0e4c34b43d800ec69/images/My_knife_jig_drawing.jpg?ver=0)

(http://img18.rajce.idnes.cz/d1801/11/11662/11662961_154b127859a75fd0e4c34b43d800ec69/images/My_knife_jig_drawing.jpg?ver=0)

P.S.: Ken, in the sketch above you can see settings for a kenjig: projection length 139 mm, support-stone distance s = 80 mm, which for stone radius 125 mm should guarantee the bevel edge 15 degrees.

As s’ = 79 mm you can see my small correction of s, which reflects the way how we measure the support-stone distance with a kenjig.  ;)
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on November 04, 2015, 02:23:10 pm
Jan, excellent drawing (and thinking). In addition to clarifying Wootz' idea, your drawing also shows more clearly how my angle setting tool works (more more clearly than my description or photo).

Good job!

Jimmy,

I agree completely; we do need more pictures! (perhaps sized a little smaller)

I am working on the situation. In the past year I have retooled from film to digital photography. New camera (Nikon D610); new printer; new film scanner; new "darkroom" (Macbook Pro)and two new lenses. Plus Lightroom CC and Photoshop CC to learn. That's a lot of new tricks for this old dog to learn. To paraphrase you, I'm doing the best I can.

I am working on series of close up photos of knife and chisel edges during stages of sharpening. I am also preparing to demonstrate the Tormek later this month. In addition to that, I have my "day job" of being a caregiver for my two grandchildren.

If Sweden would change my status from volunteer moderator to include part time paid photographer, I would give higher priority to making more photos........ :)

My camera and editing programs are also capable of video work. I believe a short video would make the kenjig very understandable to most of us who seem to have lost our verbal comprehension. Alas, this includes me as well. The constraint with video is me. That's another group of skills to learn. Those skills are on my "to do" list, but not at the top.

Don't stop grumbling. :)

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: Jan on November 04, 2015, 05:51:52 pm
Ken, your kind words pleases me.  :)

There is one practical thing I would like to mention. When we turn the adjustable stop one turn, we shorten the projection length by 2.5 mm (0.1"), which will cause an increase of the bevel angle by 1.5 degrees i.e. enlargement of the edge angle by 3 degrees. This may be a simple guidance for micro bevel sharpening.

(http://img15.rajce.idnes.cz/d1503/11/11662/11662961_154b127859a75fd0e4c34b43d800ec69/images/My_knife_jig_drawing.jpg?ver=0)

Jan
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on November 04, 2015, 08:59:39 pm
Jan, excellent thought about the amount of angle chance in a revolution of the adjustable stop screw! :)

Your drawing describes my angle setting tool "a new angle setting tool" (topic) much better than does my photograph. Would you be willing to copy and modify your drawing by substituting a single bevel (acute enough to provide clearance with the wheel) and post it on the new angle tool topic? The angle tool and kenjig really need a video someday, but, for the present, your drawing is much more clear than my photograph.

Thanks.

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: wootz on November 04, 2015, 10:25:34 pm
... I concluded that the knife jig is working fully symmetrically for knives which blades are not thicker than about 2 mm.

So, to modify the knife jig for 3 mm thick blades, for maintaining symmetry with respect to flipping, I would remove 0.5 mm from each clamp.

To modify the jig for 4 mm thick blades, I would remove 1 mm from each clamp.

Jan

Hi Jan. The source of asymmetry is that the knife jig has only one adjustable jaw, so the fixed is the one to work on.
Title: Re: Long Knife Jig asymmetry problem
Post by: wootz on November 04, 2015, 10:28:48 pm
There is one practical thing I would like to mention. When we turn the adjustable stop one turn, we shorten the projection length by 2.5 mm (0.1"), which will cause an increase of the bevel angle by 1.5 degrees i.e. enlargement of the edge angle by 3 degrees. This may be a simple guidance for micro bevel sharpening.
Jan

A clever observation, Jan.
I've added it to my collection of Jan's adjustments.

This collection already has your sketch of the knife position in the jig, and this:
"One revolution of the micro-adjust wheel means elevation of the universal support by 1.5 mm (0.06"). This will increase the distance between the support and the stone, and cause that the chisel bevel angle will typically increase by 1 degree."

Much appreciated.
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on November 05, 2015, 02:56:11 am
I second Wootz' comments.

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: Herman Trivilino on November 05, 2015, 03:50:31 am
I realized the problem with adjustments every time as the knife is flipped over, is that when I have to alternate sides, it is impossible to maintain strictly the same angle, and because of that I cannot get sharp edge.

How is it that the asymmetry prevents you from getting a sharp edge? I would think it would simply make one vbevel wider than the other, and I can see how that wouldn't be desirable, but I don't see how it could affect sharpness.
Title: Re: Long Knife Jig asymmetry problem
Post by: wootz on November 05, 2015, 09:29:43 am
Hi Herman, what i was saying is that when I compensate for the bevel asymmetry by rotating the jig adjustable stop every time as the knife is flipped over, it is impossible to maintain exactly the same grinding angle, and therefore get a sharp edge, in a sharpening routine where passes are made alternating the blade sides.
And I alternate the blade sides with every pass in the last, finest, stages, on #4000 SJ and honing leather wheel, where 1 degree difference can dull the formed edge.
Title: Re: Long Knife Jig asymmetry problem
Post by: Jan on November 05, 2015, 11:26:14 am

Hi Jan. The source of asymmetry is that the knife jig has only one adjustable jaw, so the fixed is the one to work on.

Hi Vadim. Even though it is only one adjustable jaw, the original knife jig design guarantees bevel symmetry for thinner knives. If you filed away 1 mm from the static clamp only, you have disrupted this initial symmetry for thin knifes and not created fully symmetrical jig for thicker knives.

In my understanding, when modifying the jig clamps, we should proceed symmetrically, and remove the same amount of material from both clamps; 0,5 mm for 3 mm blades and 1 mm for 4 mm blades. This approach should ensure the bevel symmetry also for thicker knives.  :)

Jan
Title: Re: Long Knife Jig asymmetry problem
Post by: wootz on November 05, 2015, 11:41:41 am
As Goethe said, theory is grey, my friend, but the tree of life is evergreen.
Title: Re: Long Knife Jig asymmetry problem
Post by: Jan on November 05, 2015, 11:42:31 am
Jan, excellent thought about the amount of angle chance in a revolution of the adjustable stop screw! :)

Your drawing describes my angle setting tool "a new angle setting tool" (topic) much better than does my photograph. Would you be willing to copy and modify your drawing by substituting a single bevel (acute enough to provide clearance with the wheel) and post it on the new angle tool topic? The angle tool and kenjig really need a video someday, but, for the present, your drawing is much more clear than my photograph.

Thanks.

Ken

Ken, to modify the drawing is not so easy because it was sketched by hand and then scanned, so I cannot change some of the parameters and generate a new drawing.

But if you give me enough time, I'll think how to adjust the sketch for your topic "a new angle setting tool".  :)

Jan
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on November 05, 2015, 12:00:35 pm
Thanks, Jan. anything you can do will be most appreciated. No rush. I wish I had acquired drawing skill; it is a most useful skill.

Regarding removing material from both sides of the knife jig: If we remove enough material from the fixed side to allow the knife blade to be coplanar with the axis of the jig, why do we need to remove anything from the adjustable jaw, the clamping jaw? This assumes the adjustable jaw can be loosened enough to allow the knife to fit and be tightened.

Modifying the knife jig like this would make having an extra jig preferable. Care should also be taken not to remove enough material to weaken the jig.

Fine adjustments for thickness might be made with paper, cardboard or thin pieces of "feeler gage".

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: Jan on November 05, 2015, 06:14:32 pm
Ken, you're correct.   :)

In my recommendations, I was guided by the intention that the modified knife jig should provide the same comfort as the original one. Under the comfort I understand margins for the tightening knob and the parallelism of the clamps after tightening the blade. My recommendations are still valid, but are not necessary conditions for proper function of the modified jig.

As confirmed by Vadim, it is sufficient to file away some material from the static clamp only.

Jan

Title: Re: Long Knife Jig asymmetry problem
Post by: Jan on November 05, 2015, 06:18:30 pm
As Goethe said, theory is grey, my friend, but the tree of life is evergreen.

Vadim, thanks for your response through an appropriate quote. Appreciated.  :)

Jan
Title: Re: Long Knife Jig asymmetry problem
Post by: Herman Trivilino on November 06, 2015, 02:24:12 am
There can be only one knife thickness for which the bevel angle will be the same on both sides of the knife. A thinner knife will have a wider bevel on one side, a thicker knife on the other side. Thus, it's possible to accommodate a thicker knife by removing some metal from only one side of the jig, but only up to a limit. At some point a knife that's thicker yet will need to have additional metal removed from the other side, too.
Title: Re: Long Knife Jig asymmetry problem
Post by: Jan on November 06, 2015, 05:51:01 pm
Vadim, could you please estimate the size of the asymmetry before modifying the clamp? I think how much wider (in mm) was the bevel on one side than the other side?

If I knew the bevel angle, blade thickness and the radius of your wheel, I could try to calculate it. This would allow to understand better the source of the bevel asymmetry.  :)

Jan
Title: Re: Long Knife Jig asymmetry problem
Post by: Jan on November 18, 2015, 04:17:03 pm
There can be only one knife thickness for which the bevel angle will be the same on both sides of the knife. A thinner knife will have a wider bevel on one side, a thicker knife on the other side. Thus, it's possible to accommodate a thicker knife by removing some metal from only one side of the jig, but only up to a limit. At some point a knife that's thicker yet will need to have additional metal removed from the other side, too.

Herman you are correct.  :)

Today I have carefully measured the dimensions of the knife jig and came to the conclusion that the fixed side of the jig is 1 mm (2.5/64") below the longitudinal jig axis, around which the adjustable stop revolves.

So the knife jig is perfectly symmetrical for 2 mm (5/64") thick knife blade. The accuracy of my measurements is +/- 0.2 mm.

Jan
Title: Re: Long Knife Jig asymmetry problem
Post by: carvingcat on January 05, 2016, 04:34:52 pm
I had this exact same problem with the Tormek SVM-100 that came as part of a kit with my 1206 bought a few years ago, and after trying it out once (on one of my cheaper 8" chef's knifes) I found the results so bad (my knife sliced diagonally after!) I put the jig away until recently, putting it down to my novice sharpening skills. I use my Tormek almost exclusively for sharpening my carving gouges and so I forgot all about the SVM-100 until recently when I thought I'd have another go before selling it.

Looking at it again it is clearly offset, and the only option is to reset the angle for each side of the blade - it is a bit of a hassle but I've now had some reasonable results, I'll try to upload some images to illustrate.

Title: Re: Long Knife Jig asymmetry problem
Post by: carvingcat on January 05, 2016, 05:06:01 pm
Here's the jig holding my thinnest knife (kai shun 8" chef's), you can see the knife is not inline with the jig, even the larger cast part of the jig appears to bend away from the shaft...


(https://farm2.staticflickr.com/1579/23825106199_0df0760854.jpg) (https://flic.kr/p/CikU26) , (https://farm2.staticflickr.com/1541/24084863482_bc28bbb3b0.jpg) (https://flic.kr/p/CGidNW)




And here it shows how much the angle changes when turning the jig over...


(https://farm2.staticflickr.com/1529/23566107613_cb0d95a0b3_b.jpg) (https://flic.kr/p/BUssLe)
(https://farm2.staticflickr.com/1659/24166828976_b9367954a3_b.jpg) (https://flic.kr/p/CPxji7)


The only difference in the two images above is that the jig has been turned over, the angle has changed significantly
Title: Re: Long Knife Jig asymmetry problem
Post by: Jan on January 05, 2016, 06:20:52 pm
Welcome to the forum carvingcat.  :)

In this thread we have discussed mainly the Tormek knife jig SVM-45 and I am not quite sure if we can apply the conclusions also to your SVM-100 jig.

Based on Wootz experience the usage of the knife jig SVM-45 for thick knives (more than 3 mm) results in uneven bevel angles. He solved this problem by filling away 1 mm from the static clamp.

Based on my measurements the knife jig SVM-45 works perfectly symmetrically for 2 mm thick knife blade.

Because it is hardly imaginable that your knife is substantially thinner than 2 mm, it is probably necessary to look for the fault in the jig, or in the way the knife is mounted into the jig. When the blade is tapered and the jig grips only 2 or 3 mm of the knife’s blade, than the knife is often not sufficiently firmly mounted in the jig.

Jan
Title: Re: Long Knife Jig asymmetry problem
Post by: Edwe on January 05, 2016, 06:51:27 pm
Hia All

This is very sad to read and I think Tormek must ansver this and fix it.
I am not in the skill for sharpening on freehand and is very dependent on the jigs.

In Swedish
Tormek ni måste fixa detta, antingen byta ut jiggarna mot fungerande eller föreslå en lösning.

Best regards Edwe
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on January 05, 2016, 08:02:08 pm
I have never had much luck with the anglemaster on very shallow surfaces. (Chisels and plane blades are fine.) I would substitute something thin and flat like a plastic gift card. Then, make a cradle to hold the jig with the  knife. With another block of wood, mark the position of the knife edge. Flip the jig over and note the knife edge location difference. Add a shim of half the difference in thickness.

Sorry, this needs photos or a video.

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: stevebot on January 05, 2016, 11:53:07 pm
For a look at another sharpener's solution to this problem, see
http://amktactical.com/epages/3c926a50-9aba-43a5-9571-098ee03f1288.sf/en_US/?ObjectPath=/Shops/3c926a50-9aba-43a5-9571-098ee03f1288/Products/24
Watch the video from about 1:30.
Title: Re: Long Knife Jig asymmetry problem
Post by: Elden on January 06, 2016, 01:01:09 am
   I like that, Steve. That is a quick and easy fix for the asymmetry problem that thin knives produce. The process could easily adapted to the Tormek knife jigs. For thick knife problems, one would still have to modify the jigs or flip the knife over in the jig. That electronic protractor is nice as well.
Title: Re: Long Knife Jig asymmetry problem
Post by: grepper on January 06, 2016, 05:40:12 am
This is slightly off the off-center topic, but might save you a couple of $$.  I have a similar inexpensive digital protractor.  I think the one shown in the video is 0.1 degrees accurate:
http://tinyurl.com/hpbak5d

The one I have specs out to 0.2 degrees accurate:
http://www.amazon.com/gp/product/B006JR8XBG?psc=1&redirect=true&ref_=oh_aui_search_detailpage

I got it for hanging pictures.  I quit using it because I could tilt the picture frame and it did not register on the protractor.  I can plainly see level better than 0.2 degrees.  I get better results using a good quality bubble level.  0.1 degrees is 2X better than the one I have, but still I would rather use a bubble level.  It’s amazing how well the eye can judge the short distance at the ends of a bubble.

Accurate digital protractors are far more expensive.  I though I could get away with a cheaper one, I was laboring under a delusion.  After hanging a picture I could easily see it was out of level even though the cheapo protractor indicated level.

Onion other hand, I suspect this one would be just fine:
http://tinyurl.com/jyo3fsb
Title: Re: Long Knife Jig asymmetry problem
Post by: Elden on January 06, 2016, 06:23:25 am
   Thanks for the warning, Mark. I am sure you are right, you get what you pay for. While not being extremely accurate, I have used the dial type magnetic protractor before for other projects. Here is a cheap one.

http://www.homedepot.com/p/Johnson-Magnetic-Angle-Locator-700/100161689?cm_mmc=Shopping%7cTHD%7cG%7c0%7cG-BASE-PLA-D25T-HandTools%7c&gclid=CjwKEAiA8K20BRDetNv3p6DNhXwSJADSwa3t8oF9f0KKDDSAd6szOcRKMtkwK7XSZ-LvwX9ieR9lsRoCpBfw_wcB&gclsrc=aw.ds
Title: Re: Long Knife Jig asymmetry problem
Post by: grepper on January 06, 2016, 06:41:29 am
And if you need to know the angle, like in the belt grinder video, a bubble is useless.
Title: Re: Long Knife Jig asymmetry problem
Post by: carvingcat on January 06, 2016, 03:15:37 pm
Welcome to the forum carvingcat.  :)

In this thread we have discussed mainly the Tormek knife jig SVM-45 and I am not quite sure if we can apply the conclusions also to your SVM-100 jig.

Based on Wootz experience the usage of the knife jig SVM-45 for thick knives (more than 3 mm) results in uneven bevel angles. He solved this problem by filling away 1 mm from the static clamp.

Based on my measurements the knife jig SVM-45 works perfectly symmetrically for 2 mm thick knife blade.

Because it is hardly imaginable that your knife is substantially thinner than 2 mm, it is probably necessary to look for the fault in the jig, or in the way the knife is mounted into the jig. When the blade is tapered and the jig grips only 2 or 3 mm of the knife’s blade, than the knife is often not sufficiently firmly mounted in the jig.

Jan


Thanks Jan, the SVM-45 is identical to the SVM-100 apart from the width of the blade jaws which are 100mm on the SVM-100 and (I assume) 45MM on the SVM-45, they both function in exactly the same way. The knife I'm using here is exactly 2mm thick, and the more I look at the jig the more I think it could be a defective item.


In the first image you can see how the lower jaw deviates from the straight line at the arrow, the other images showing the angle refer to the blade angle (not the bevel), the anglemaster reading was taken from one side of the blade and not changed for the other - it is to illustrate the different angle of the blade resting against the stone, if the jig was accurate then surely the blade should be resting flat against the anglemaster (at 16 degrees) in both images, not just on one side.


(https://farm2.staticflickr.com/1500/24127800801_393f6c34fc_b.jpg) (https://flic.kr/p/CL6hzx)


(https://farm2.staticflickr.com/1463/23583613773_0c413575fa.jpg) (https://flic.kr/p/BW1bJz)
(https://farm2.staticflickr.com/1698/23582216474_d85e16c3c6.jpg) (https://flic.kr/p/BVT2nd)


Note the anglemaster is set to 16 degrees in both images;


(https://farm2.staticflickr.com/1608/24184682646_724e55c7ed_n.jpg) (https://flic.kr/p/CR7Pz1)
(https://farm2.staticflickr.com/1473/23583952053_f58ef42d55_n.jpg) (https://flic.kr/p/BW2VhZ)
Title: Re: Long Knife Jig asymmetry problem
Post by: carvingcat on January 06, 2016, 03:27:19 pm
I'm very tempted to just knock this so that it runs straight, but I'm worried it might break - any thoughts on the alloy?


(https://farm2.staticflickr.com/1500/24127800801_393f6c34fc.jpg) (https://flic.kr/p/CL6hzx)
Title: Re: Long Knife Jig asymmetry problem
Post by: WolfY on January 06, 2016, 04:53:09 pm
Hi guys, I'm new here and this is my first reply :)

The problem you describe about the angle change as the jig is turned 180 dgrs is of little concern to me too.
But let say for the regular user with the standard jig that use it for years and never got into this measurements, is it a real problem? Let say the sharpening angle difference is 2~3 dgrs.
How much tolerance will you accept?

Carvingcat, Is your jig bent or was it so originally?
Title: Re: Long Knife Jig asymmetry problem
Post by: Edwe on January 06, 2016, 05:03:55 pm
God posting carvingcat, I love pictures.. makes much more sense :)

So this isnt only the long knife jig, maybe all jigs?
I still think Tormek have to fix this, chims or whatever.
Title: Re: Long Knife Jig asymmetry problem
Post by: Elden on January 06, 2016, 05:27:39 pm
   Welcome to the forum, Wolfy. As Stig (Stickan) has posted, it really is a cosmetic situation.

http://www.tormek.com/forum/index.php?topic=2577.msg13542#msg13542
Title: Re: Long Knife Jig asymmetry problem
Post by: WolfY on January 06, 2016, 05:52:37 pm
Thanks Elden.
Title: Re: Long Knife Jig asymmetry problem
Post by: carvingcat on January 06, 2016, 07:10:12 pm
Hi guys, I'm new here and this is my first reply :)

The problem you describe about the angle change as the jig is turned 180 dgrs is of little concern to me too.
But let say for the regular user with the standard jig that use it for years and never got into this measurements, is it a real problem? Let say the sharpening angle difference is 2~3 dgrs.
How much tolerance will you accept?

Carvingcat, Is your jig bent or was it so originally?


This is how it came from new, the original box was undamaged so there was no problem during transport, but to be honest I think it is bent, I'd be very interested to compare it against another one - I can't decide whether to try to straighten it, risking breaking it, or just leave it as it is and adjust the angle for each side.


   Welcome to the forum, Wolfy. As Stig (Stickan) has posted, it really is a cosmetic situation.

http://www.tormek.com/forum/index.php?topic=2577.msg13542#msg13542 (http://www.tormek.com/forum/index.php?topic=2577.msg13542#msg13542)


I think it is more than a cosmetic issue, after the first run it was impossible to cut a thin slice of garlic as the knife would slip out sideways on the cut.
Having taken much more time I'm now able to get a superb edge, but I have to do 2 strokes on one side, then flip the knife jig over and completely re-set the desired angle and do 2 strokes on the other. After testing with the knife still in the jig, if it needs further refinement I repeat the process again. It takes time, and it is a pain re-setting the angle (requiring 3 to 4 turns of the adjustable stop) but the final results are impressive - I can slice garlic as thinly as I'd ever need :)



Title: Re: Long Knife Jig asymmetry problem
Post by: Jan on January 06, 2016, 07:54:46 pm

Thanks Jan, the SVM-45 is identical to the SVM-100 apart from the width of the blade jaws which are 100mm on the SVM-100 and (I assume) 45MM on the SVM-45, they both function in exactly the same way. The knife I'm using here is exactly 2mm thick, and the more I look at the jig the more I think it could be a defective item.

You are welcome, Carvingcat! Congrats to your perfect photo documentation.  :)

You are probably correct, your knife jig could be defective. Before trying to straighten the jig I would recommend to experiment with centring the knife in the jig using suitable shim (spacer). See the post #37 of this thread.

Jan
Title: Re: Long Knife Jig asymmetry problem
Post by: WolfY on January 07, 2016, 03:00:00 am
This is how it came from new, the original box was undamaged so there was no problem during transport, but to be honest I think it is bent, I'd be very interested to compare it against another one - I can't decide whether to try to straighten it, risking breaking it, or just leave it as it is and adjust the angle for each side.
http://www.tormek.com/forum/index.php?topic=2577.msg13542#msg13542 (http://www.tormek.com/forum/index.php?topic=2577.msg13542#msg13542)

Carvingcat,
To me it looks like it getting the bent after tightening the screw to hard. There is a lot of torque power there. Maybe it was bent originally too, which add to the bent.
With such a bent no wonder you get large angle difference on the knife sides.

As this also bothered me even before seeing your pic's, so I have worked on some ideas on a self centering auto protrusion jig to keep at least the jig end to knife edge as constant as possible.
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on January 07, 2016, 03:22:06 am
Outstanding photography, carvingcat! I will have to clean up my act to keep up with the newer members. Out of curiosity, what lighting do you use?

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on January 07, 2016, 03:29:20 am
WolfY,

I am of two minds on this. I appreciate accuracy. I also realize that this sharpening was traditionally done by hand and without jigs. I tend to think that historically a couple degrees would not matter.

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: Elden on January 07, 2016, 04:39:46 am
Ken and Zeev,

   Check out the accuracy or lack thereof of this sharpening process.

https://www.youtube.com/watch?v=k5yENFigHEA

The movement of the knife in the line of the wheel travel when the grinding was started, really jumped out at me. I imagine he gets some Sharp knives, however. Sounds like he does quite a number of knives.

   By the way, I am glad I have a Tormek! Notice the sound of that unit slowing down when under a load.
Title: Re: Long Knife Jig asymmetry problem
Post by: carvingcat on January 07, 2016, 10:13:40 am
Outstanding photography, carvingcat! I will have to clean up my act to keep up with the newer members. Out of curiosity, what lighting do you use?

Ken


Thank you Ken, here I'm using a couple of Elinchrom D-Lite strobes with some 66cm softboxes attached, set either side of the shot. It's my standard setup for photographing my carving work (www.perrylancaster.com if you're interested). I love them, but any good quality lights will give the same results...
Title: Re: Long Knife Jig asymmetry problem
Post by: WolfY on January 07, 2016, 10:19:34 am
Ken and Zeev,

   Check out the accuracy or lack thereof of this sharpening process.

https://www.youtube.com/watch?v=k5yENFigHEA

The movement of the knife in the line of the wheel travel when the grinding was started, really jumped out at me. I imagine he gets some Sharp knives, however. Sounds like he does quite a number of knives.

   By the way, I am glad I have a Tormek! Notice the sound of that unit slowing down when under a load.

Looks terrible...
Title: Re: Long Knife Jig asymmetry problem
Post by: carvingcat on January 07, 2016, 10:30:16 am
WolfY,

I am of two minds on this. I appreciate accuracy. I also realize that this sharpening was traditionally done by hand and without jigs. I tend to think that historically a couple degrees would not matter.

Ken


I think if you were sharpening knives by hand all day as a full time job you'd probably be able to get results as good as any of us using the jigs! I tried sharpening a couple of small knives by hand too, and I got reasonable results (for a novice!) - but I bought into the Tormek system for controlled accuracy of sharpening, and I'm delighted with the results for my gouges, it has to be said I'm obsessive about my knives!
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on January 07, 2016, 12:00:05 pm
carvingcat,

I looked at your website. Very nice work! I recommend the forum members and guests also check it out.

Keep up the good work and keep posting.

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: carvingcat on January 07, 2016, 01:07:38 pm
Thank you Ken :)
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on January 07, 2016, 10:36:39 pm
Elden,

What  struck  me as odd about the you tube was that the grinding wheel had a distinct hollow. The presenter later mentioned this. I have not yet watched the first three in the series. The guy seems experienced, however, I was surprised that anyone would make a video with a wheel in obvious need of truing.

I have become a believer in frequent, light truing.

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: Jan on January 08, 2016, 03:10:41 pm
When I watched the video in question, I was horrified.  :o

Positioning the knife so obliquely to the grindstone cannot lead to sharpening a consistent knife edge. Also the method of using sharpening steel was not correct. The beginning of the video reminds me of prestidigitator’s performance with grinder and knife.  ;)

Jan
Title: Re: Long Knife Jig asymmetry problem
Post by: Elden on January 08, 2016, 07:20:02 pm
    I told you in the past that your English is probably better than mine, Jan. You made me use the dictionary with that post.  ??? :)
Title: Re: Long Knife Jig asymmetry problem
Post by: Jan on January 08, 2016, 09:15:17 pm
Sorry Elden, it was not my intention!  :)

When I realized how great is the change in the bevel angle when the knife meets the stone at an oblique angle, I began to think about how to use it for sharpening scissors which don't have the same bevel angle along their entire length.  ;)

Jan
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on January 09, 2016, 01:28:30 am
It is easy to think of a consistent bevel obtained by careful use of a jig as for appearance. The other factor, perhaps more important, is that careful use of a jig with the same settings over time will result in less metal being removed.

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: grepper on January 09, 2016, 04:41:04 pm
If you examine a freehand sharpened knife under a microscope, there is a lot of micro beveling back from the edge.  Well, at least when I do it.  ::)

So all of the passes that I took back from the edge were just wasted time and like Ken said wasted metal.  Obviously, if you don’t hit the edge the knife is not getting any sharper.

Consider what happens if you hit the edge on part of the blade, but miss on others because the blade was tilted away from the edge.  Obviously, eventually a perfectly useable edge can be created, but it’s easy to imaging what’s going on down there and easy to see under a scope.
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on January 09, 2016, 04:47:13 pm
grepper,

On a bandsaw blade, that pattern might be called"skip tooth". :)

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: carvingcat on January 14, 2016, 12:50:11 pm
After a bit of advice from Tormek Support I've managed to get my jig sorted! It turns out it was bent when I received it and so the results were not as expected, but I have managed to gently knock it back straight and now it performs perfectly. I straightened it by eye, and to check it was going to be correctly set up I marked the stone with a pencil to see where the blade would touch on either side. The images show very minor deviation now and I imagine any difference in bevel angle will be insignificant. Thanks to Stig for the advice!



(https://farm2.staticflickr.com/1500/24127800801_393f6c34fc_z.jpg) (https://flic.kr/p/CL6hzx)
Before


(https://farm2.staticflickr.com/1539/24005698069_5187ebf1d8_z.jpg) (https://flic.kr/p/CzitG2)
After


(https://farm2.staticflickr.com/1541/24077907360_9e5946c778_z.jpg) (https://flic.kr/p/CFFyZN)


(https://farm2.staticflickr.com/1587/24347275606_d84c1d4043_z.jpg) (https://flic.kr/p/D6u9MU)


(https://farm2.staticflickr.com/1448/23746669043_523b0995a1_z.jpg) (https://flic.kr/p/CbpTok)
The lines show negligible difference for each side of the blade







Title: Re: Long Knife Jig asymmetry problem
Post by: Jan on January 14, 2016, 01:35:28 pm
Thank you Carvingcat for posting information concerning your bent knife jig and congrats to your successful straightening it.  :)

The measurement you have done is not sufficient, but necessary condition for its symmetrical functioning.

Jan
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on January 15, 2016, 03:19:26 am
A verypractical suggestion. One for the memory bank!

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: Herman Trivilino on January 15, 2016, 04:51:49 am
After a bit of advice from Tormek Support I've managed to get my jig sorted!

Did they tell you straighten it out? So you were no longer afraid you might break it?
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on January 15, 2016, 11:19:26 am
I purchased a used (abused?) roughing gouge. I think the previous owner had a major catch with it. It was bent where it entered the handle. After much thought and concern, I finally put it in my woodworking vise and slowly leaned on it. To my pleasant surprise, straightening it took much less time than debating the issue. The solution was gradually applying the pressure.

Worst case scenario, T C was that you might have to replace the part or look for another jig. In the process you learned a new skill. I would call that a win. I do see Herman's point. Metal is often more brittle than we realize.

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: Jan on January 15, 2016, 02:40:52 pm
A very practical suggestion. One for the memory bank!

Ken

''But let your communication be, Yea, yea; Nay, nay: for whatsoever is more than these cometh of evil.''  :)

Jan
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on January 15, 2016, 04:34:07 pm
Great quote, Jan. Source?

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: Jan on January 15, 2016, 05:04:33 pm
King James Bible, Matthew 5:37.
http://biblehub.com/matthew/5-37.htm (http://biblehub.com/matthew/5-37.htm)

Jan
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on January 15, 2016, 08:28:43 pm
Interesting.

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: carvingcat on January 16, 2016, 04:51:50 pm
After a bit of advice from Tormek Support I've managed to get my jig sorted!

Did they tell you straighten it out? So you were no longer afraid you might break it?


That's correct Herman, Tormek said if it broke they would send me a replacement jig so I had the confidence to go ahead and bend it straight.
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on January 16, 2016, 05:27:13 pm
I call that excellent customer support.

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: wootz on February 05, 2016, 11:44:22 am
For a look at another sharpener's solution to this problem, see
http://amktactical.com/epages/3c926a50-9aba-43a5-9571-098ee03f1288.sf/en_US/?ObjectPath=/Shops/3c926a50-9aba-43a5-9571-098ee03f1288/Products/24
Watch the video from about 1:30.

Thanks for that, Steve. Have you guys watched it?
Recently I got a few knives which to bevel properly I couldn't do without shims, so I watched that video, and applied their approach to SVM-45.
Shim is placed on the bottom jaw, i.e. between the static part of the clamp and the blade.
Maths for Tormek SVM-45 are as follows.

Spacing from the centreline of the handle to the bottom of the knife clamp (the static part of the clamp) is 1.5mm.
Ideal for 3mm blades, but well acceptable to 2.5-3.5mm thick as well.

For knives outside this range, shims can be used. I use blades from a Feeler Gauge with 1cm wide blades as shims.
Measure thickness of the knife at the clamping spot, and divide by 2 - you get spacing to the centreline of the knife.
Difference between 1.5mm and halved knife thickness is filled with a shim.

Example 1
Knife thickness 1.7mm, divided by 2 = 0.85mm.
1.5mm - 0.85mm = 0.65mm shim.

Obviously, for knives thicker than 3mm you should not put shims in the standard SVM-45 - for them I use a second jig with 1mm filed off the static clamp (described earlier in this topic).
Spacing from the centreline of the handle to the bottom of this jig is 2.5mm.

Example 2
Knife thickness 4.6mm, divided by 2 = 2.3mm.
2.5mm - 2.3mm = 0.2mm shim.

These calculations have been proved practically.

Hope this will be useful to you where a perfectly symmetrical bevel is required.
Title: Re: Long Knife Jig asymmetry problem
Post by: Jan on February 05, 2016, 05:50:55 pm
Wootz, thank you for sharing the practical examples.  :)

I have only a minor comment. Previously I have expressed my opinion that the knife jig works fully symmetrically for knives which blades are about 2 mm thick. (Reply #31 of this topic.)

Recently I have specified this value to 2.5 mm. It is the thickness of the steel guide bar (1) of the Small Knife Holder.

(http://img21.rajce.idnes.cz/d2102/11/11771/11771137_37021e568ec44478b9ce7dc74d286378/images/Small_knife_jig_640.jpg?ver=0)

This thickness guarantees that the Small Knife Holder works symmetrically and the same is true for the knife blade of the same thickness in the Knife Jig.

Jan
Title: Re: Long Knife Jig asymmetry problem
Post by: wootz on February 06, 2016, 01:04:15 am
Brilliant thinking, Jan!
Thank you for the correct figure. I happily stay corrected - the exact clamp centreline is 1.25mm.
Title: Re: Long Knife Jig asymmetry problem
Post by: Jan on February 06, 2016, 01:19:36 am
You are welcome, Wootz!  :)
I am also happy that it was possible to determine this important figure in this elegant way.

Jan
Title: Re: Long Knife Jig asymmetry problem
Post by: Elden on February 06, 2016, 06:06:32 am

(http://img15.rajce.idnes.cz/d1503/11/11662/11662961_154b127859a75fd0e4c34b43d800ec69/images/My_knife_jig_drawing.jpg?ver=0)

P.S.: Ken, in the sketch above you can see settings for a kenjig: projection length 139 mm, support-stone distance s = 80 mm, which for stone radius 125 mm should guarantee the bevel edge 15 degrees.

As s’ = 79 mm you can see my small correction of s, which reflects the way how we measure the support-stone distance with a kenjig.  ;)

Jan,
   Out of curiosity, is the above mentioned bevel angle a measurement of the edge angle or of the chord? The drawing appears to picture the chord, however, I know that is not what you were illustrating.
   Does the KenJig set up for the edge angle or the chord angle? That is really what I am wondering about.
Title: Re: Long Knife Jig asymmetry problem
Post by: Jan on February 06, 2016, 10:45:49 am
Elden, you are correct, at the scale my drawing is shown, it is not recognisable what kind of line segment is delimiting the bevel angle.

Let me illustrate it on a chisel type bevel. Chord has both endpoints A and B on the grindstone and against chord we measure the hollow. The chord angle, not shown in the drawing, is 28.1o.

(http://img21.rajce.idnes.cz/d2102/11/11771/11771137_37021e568ec44478b9ce7dc74d286378/images/ELDEN-CHISEL_25_deg_125mm_700_chord_1.jpg?ver=0)

Tangent line touches the grindstone at A and never enters the grindstone’s interior. Tangent to the grindstone is square to the radius.

The line which delimits the edge angle is a tangent line segment. Please note that in the  example shown here the edge angle is 25o, while the heel angle is 31.2o.

Also Kenjig sets up for the edge angle and not the chord angle. The chord angle corresponds to the mid angle, i.e. the edge angle at the midpoint of the tool, where the hollow size is maximal.

Jan
Title: Re: Long Knife Jig asymmetry problem
Post by: Elden on February 06, 2016, 04:11:35 pm
   Thank you, Jan! That satisfies my curiosity. It really did not matter,but was a thought born out of previous discussions. Due to thickness of most knives, I suppose there would be less difference between the chord and tangents angles than that of a chisel. Thick knives might be an exception to that statement.
Edit: Because the taper ground into the knife, there really shouldn't be a great difference between thick and thin knives.
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on February 06, 2016, 04:34:33 pm
Good point, Elden.

The longest bevel I remember was the mortising chisel Jan posted a while back. A bevel that long would have considerable hollow.

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: Jan on February 06, 2016, 05:48:26 pm
Yes, Ken.  :)
For my ancient 3/4" mortise chisel the calculated hollow was some 1 mm and the Elden’s chord angle was by some 7o larger than the edge angle!  For aesthetical reasons the chisel was ground flat.

Jan
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on February 06, 2016, 08:08:30 pm
Jan,

I am pleased that you can appreciate both the logical beauty of mathematics and the aesthetic beauty of a chisel bevel.

Don't change.

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: Jan on February 07, 2016, 07:59:34 pm
Lovely and aptly said, Ken! Appreciated.  :)
Everything has its beauty and our task is to see it.
(Modified according to Confucius.)

Jan
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on February 12, 2019, 01:24:00 pm
A question from Texaspro inspired an idea. It is borrowed from sharpening skew chisels. With skew chisels, the amount of skew by setting the skew amount to a perpendicular line drawn on the grinding wheel. To draw this line, lower the support bar until it touches the grinding wheel. (Be sure the grinding wheel has been trued.) Using a fine point Sharpie marker, draw a line across the grinding wheel, using the support bar as a straightedge.

Set the jig to the desired bevel angle. With the knife jig with the knife mounted onto the support bar with the sharp edge touching the line. Without moving the grinding wheel, flip the jig over. If the knife is set symmetrically, both sides of the blade should touch the line.

This may be easier to see if the the support bar is raised to hold the knife at a right angle to the grinding wheel.

Ken

Title: Re: Long Knife Jig asymmetry problem
Post by: cbwx34 on February 12, 2019, 04:16:11 pm
A question from Texaspro inspired an idea. It is borrowed from sharpening skew chisels. With skew chisels, the amount of skew by setting the skew amount to a perpendicular line drawn on the grinding wheel. To draw this line, lower the support bar until it touches the grinding wheel. (Be sure the grinding wheel has been trued.) Using a fine point Sharpie marker, draw a line across the grinding wheel, using the support bar as a straightedge.

Set the jig to the desired bevel angle. With the knife jig with the knife mounted onto the support bar with the sharp edge touching the line. Without moving the grinding wheel, flip the jig over. If the knife is set symmetrically, both sides of the blade should touch the line.

This may be easier to see if the the support bar is raised to hold the knife at a right angle to the grinding wheel.

Ken

I (of course) ;) went and tried this on a thick (3.75mm) hunting knife... and it worked... you could easily see the difference.  (Part of me thinks this has come up before?... or maybe a "deja vu" moment)...

Anyway... give it a try!
Title: Re: Long Knife Jig asymmetry problem
Post by: Skitz on February 12, 2019, 04:36:28 pm
Hi I’m newby trying to research tormek supergrind 2000 do the new htk jigs work on that model
Cheers peter

Title: Re: Long Knife Jig asymmetry problem
Post by: cbwx34 on February 12, 2019, 05:11:29 pm
Hi I’m newby trying to research tormek supergrind 2000 do the new htk jigs work on that model
Cheers peter

Yes... the new jigs work on the 2000... there’s no difference in the basic setup in that aspect.
Title: Re: Long Knife Jig asymmetry problem
Post by: RichColvin on February 12, 2019, 05:13:58 pm
CB is right :  I use them all on my SuperGrind 2000.

Kind regards,
Rich
Title: Re: Long Knife Jig asymmetry problem
Post by: texaspro on February 13, 2019, 03:18:39 pm
A question from Texaspro inspired an idea. It is borrowed from sharpening skew chisels. With skew chisels, the amount of skew by setting the skew amount to a perpendicular line drawn on the grinding wheel. To draw this line, lower the support bar until it touches the grinding wheel. (Be sure the grinding wheel has been trued.) Using a fine point Sharpie marker, draw a line across the grinding wheel, using the support bar as a straightedge.

Set the jig to the desired bevel angle. With the knife jig with the knife mounted onto the support bar with the sharp edge touching the line. Without moving the grinding wheel, flip the jig over. If the knife is set symmetrically, both sides of the blade should touch the line.

This may be easier to see if the the support bar is raised to hold the knife at a right angle to the grinding wheel.

Ken

Thanks for the feedback Ken. However, I already know that my 2.5mm wide blade (Benchmade Mini Griptillian) in the SVM-45 is not the same on both sides. I am trying to figure out why and how to fix it. Unfortunately putting shims in the jig or grinding the jig down as Wootz suggests, is not applicable on 2.5mm wide blades (his method is more for under 2mm or over 3mm, from what I understand).

To be perfectly clear, the problem I am having is an uneven bevel (one side is higher than the other). No matter what I try, the angle is always different on one side as opposed to the other, causing the bevel to be higher on one side.

Is there a solution for this or am I just screwed? I can't be the only one that has this issue...Are people just saying, "oh well"??

Title: Re: Long Knife Jig asymmetry problem
Post by: texaspro on February 13, 2019, 03:19:05 pm
other side
Title: Re: Long Knife Jig asymmetry problem
Post by: RickKrung on February 13, 2019, 05:30:57 pm
Thanks for the feedback Ken. However, I already know that my 2.5mm wide blade (Benchmade Mini Griptillian) in the SVM-45 is not the same on both sides. I am trying to figure out why and how to fix it. Unfortunately putting shims in the jig or grinding the jig down as Wootz suggests, is not applicable on 2.5mm wide blades (his method is more for under 2mm or over 3mm, from what I understand).

To be perfectly clear, the problem I am having is an uneven bevel (one side is higher than the other). No matter what I try, the angle is always different on one side as opposed to the other, causing the bevel to be higher on one side.

Is there a solution for this or am I just screwed? I can't be the only one that has this issue...Are people just saying, "oh well"??

I find this curious and perplexing.  2.5mm should be a perfect fit for equal bevel on both sides, using the stock knife jig (SVM-45).  I've gone to the trouble of milling away some of the fixed jaw sides of several of my SVM-45s for different blade thicknesses and use shims for the varying blades.  I have done so exactly as Wootz had posted about and have one jig milled down to accept up to 4.6mm.  In my measurements and the table of shims I developed to use with the various blades, 2.5mm is a perfect fit for the unmodified knife jig, requiring no shims. 

Which side is having the larger bevel?  The fixed jaw side (bottom) or the movable (top) jaw?  Have you turned the blade over in the jig to see if the difference follows the knife or the jig?  Do you have a way to measure the bevel angle of each side (I don't, other than a laser protractor and that would be difficult to really tell.) to see if the it is different or if they are the same?

Rick
Title: Re: Long Knife Jig asymmetry problem
Post by: texaspro on February 13, 2019, 06:12:25 pm
I have calipers I can try to measure with. It'd be hard though. In person, it's definitely noticeable looking down the edge. One side is short and the other is long. Really terrible looking.
Title: Re: Long Knife Jig asymmetry problem
Post by: texaspro on February 13, 2019, 06:37:40 pm
This is a crude representation of what the bevel looks like from the side.
Title: Re: Long Knife Jig asymmetry problem
Post by: texaspro on February 13, 2019, 06:40:07 pm
BTW, thanks to many on this forum as well as a few guys on a Facebook group, the edge is super sharp. I know a lot of folks look at this and say, "if it works, don't worry about it", but I'm a perfectionist. #NeverSettle 😎
Title: Re: Long Knife Jig asymmetry problem
Post by: cbwx34 on February 13, 2019, 07:41:03 pm
Putting your pictures side by side (although I know pics can be deceiving)... it doesn't look that bad...

(https://www.tormek.com/forum/index.php?action=dlattach;topic=2577.0;attach=3050)

... asymmetry can be caused by several things...uneven to begin with can be a culprit... like I said in another message... "a guided sharpener will tell you how bad your knives were previously sharpened".  :-\  You may just need to spend a bit more time on the thin side, to even things out.

BTW, thanks to many on this forum as well as a few guys on a Facebook group, the edge is super sharp. I know a lot of folks look at this and say, "if it works, don't worry about it", but I'm a perfectionist. #NeverSettle 😎

What tips/tricks worked that got you the "super sharp" edge?
Title: Re: Long Knife Jig asymmetry problem
Post by: texaspro on February 13, 2019, 11:06:31 pm
Thank you. I know it's hard to tell, but I can tell, which is what matters, right? :-) Haha I tried to get a pic from the tip looking down the edge, but my camera wasn't having it. I'll continue to try though.

Regarding the tips to make it sharp, there were quite a few since I was a total newb to sharpening. I've learned a lot in the past few weeks. I would say the tips that helped the most was how to strop (I was going too deep/hard, too fast on the leather) and to use the 1k stone on already beveled blades - and to raise the burr across the entire blade on both sides. I plan on detailing my experience from day 1 once I get this bevel figured out. I've already started drafting it.
Title: Re: Long Knife Jig asymmetry problem
Post by: texaspro on February 14, 2019, 11:21:55 pm
I figured it out. I was not clamping the knife down with the top screw all the way down first. On the jig it says, “1” on the big knob, the “2” on the front screw, and “3” on the other side of the black knob. So, I was going in those steps to clamp it, which is very difficult. I always thought that was odd…Anyways, someone mentioned holding the clamp tight on the knife, tightening the front screw down as far as it would go and then tightening the black knob. Did that and it eliminated the angle difference. Phew!!

I also put these $8 pads that my buddy Pratt makes and sells, on the clamp jaws, which might have helped a little too. https://www.ebay.com/itm/Adhesive-Felt-Pads-for-Tormek-Knife-Jigs-Improved-Grip-Blade-Protection-2-Sets/192808509934?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
Title: Re: Long Knife Jig asymmetry problem
Post by: cbwx34 on February 15, 2019, 01:51:26 am
I figured it out. I was not clamping the knife down with the top screw all the way down first. On the jig it says, “1” on the big knob, the “2” on the front screw, and “3” on the other side of the black knob. So, I was going in those steps to clamp it, which is very difficult. I always thought that was odd…Anyways, someone mentioned holding the clamp tight on the knife, tightening the front screw down as far as it would go and then tightening the black knob. Did that and it eliminated the angle difference. Phew!!

I also put these $8 pads that my buddy Pratt makes and sells, on the clamp jaws, which might have helped a little too. https://www.ebay.com/itm/Adhesive-Felt-Pads-for-Tormek-Knife-Jigs-Improved-Grip-Blade-Protection-2-Sets/192808509934?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

It is a tad confusing... the “1” is actually supposed to be telling the user to 1st loosen the big knob...

(https://www.tormek.com/forum/index.php?action=dlattach;topic=2577.0;attach=3054)

... at any rate, glad you got it figured out!
Title: Re: Long Knife Jig asymmetry problem
Post by: texaspro on February 15, 2019, 04:04:37 am
Ah, that makes sense...
Title: Re: Long Knife Jig asymmetry problem
Post by: RickKrung on February 15, 2019, 06:24:19 am
I figured it out. I was not clamping the knife down with the top screw all the way down first. On the jig it says, “1” on the big knob, the “2” on the front screw, and “3” on the other side of the black knob. So, I was going in those steps to clamp it, which is very difficult. I always thought that was odd…Anyways, someone mentioned holding the clamp tight on the knife, tightening the front screw down as far as it would go and then tightening the black knob. Did that and it eliminated the angle difference. Phew!!
...snip...

Yes, these jigs are essentially parallel clamps and they work best when the workpiece is clamped as parallel as possible.  Hard to tell when many knives have such narrow spines that are unground, parallel steel. 

Yesterday, motivated by your issue, I started doing some testing, with a surface plate, gauge blocks, calipers and a height gauge, but I used a flat piece of steel for making measurements rather than an actual blade.  After a lot of work, I simply demonstrated to myself that despite my perceptions of how well a blade might be clamped by looking at the gaps at the front of the jaws, the blade is held the most parallel, in the same plane as the jig centerline, when the top jaw, behind the front screw, is the most parallel with the lower jaw.  (If prompted, I will inflict upon everyone all the gory details, tables, graphs and pictures, so be careful what you ask for ::)

My take away is that one should open the screws when inserting a blade, tighten the front screw until it gets a little snug and then tighten the rear screw.  And then check how parallel the inside jaw surfaces - from the are, by eye.  Adjust BOTH screws, as needed, until the jaws are as parallel as you can get them.  Don't worry about gaps at the front of the jaws where the blade is held, just being sure it is held securely enough that it won't shift during use.  (Set screw used in place of the large knob for these tests only)
(https://www.tormek.com/forum/index.php?action=dlattach;topic=2577.0;attach=3058)

I think what texaspro posted about holding the knife in the jig jaws and then tightening the screws in order is a good general approach.  I think it doesn't go far enough because it doesn't include checking for and adjusting for parallelism of the jaws. 

One noteworthy observation is that it is possible to bend the top jaw with the rear screw, which I think is unnecessary. Only use as much pressure as needed to securely hold the blade. 

Rick
Title: Re: Long Knife Jig asymmetry problem
Post by: texaspro on February 15, 2019, 06:54:12 am
#1 - wow, that's just awesome. You must have genuinely been curious about these jaws to go through all of that!

#2 - Interesting idea. Did you try it the way I suggested and was it offline? Was there any method that yielded an offline grip? I want to be certain I did indeed resolve the issue and didn't just get lucky on this one, before moving to another knife. Your setup is great!
Title: Re: Long Knife Jig asymmetry problem
Post by: RickKrung on February 15, 2019, 07:14:34 am
#1 - wow, that's just awesome. You must have genuinely been curious about these jaws to go through all of that!

#2 - Interesting idea. Did you try it the way I suggested and was it offline? Was there any method that yielded an offline grip? I want to be certain I did indeed resolve the issue and didn't just get lucky on this one, before moving to another knife. Your setup is great!

#1 - yes, I was really curious, but also perplexed.  As some may think but have not said publicly, I can go a bit "over-the-top" on things, sometimes... 

And...

#2 - Actually, I'm not entirely clear on what you mean by an "offline" grip.  Do you mean that the blade was out of line with the jig centerline?  That makes sense as that is what I meant by "canted". 

I only tested the surrogate blade when the jaws were either parallel or the top jaw was significantly canted upward causing the blade to be canted downward.  I think the only way to effectively grip a blade and have the top jaw canted is if it is canted upward.  I think it would not make any difference, as long as the blade was caused to be canted also. 

I think you should be safe, just making sure the jaws are parallel and firmly gripping the blade.  It would be good if you tested it, however, to satisfy yourself.  I would use some "test" knives for it. 

Rick
Title: Re: Long Knife Jig asymmetry problem
Post by: cbwx34 on February 15, 2019, 04:36:27 pm
Rick is "spot on" in his assessment.

I think "offline" means getting a blade that is the appropriate width, to grind one side more than the other because it wasn't clamped correctly.  The answer to that would be yes... as Rick points out, it will cant the blade... in fact, there is a post of a user adjusting the knife by manipulating the two screws HERE (https://www.tormek.com/forum/index.php?topic=3249.msg19115#msg19115).
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on February 15, 2019, 05:38:22 pm
We are expecting a lot from one relatively inexpensive knife jig. We expect it to accurately grind both bevels of knives with quite a range of thicknesses and blades which are are not parallel.I think Wootz is moving in the right direction by dedicating four jigs to achieve this goal.

I believe the final solution will be one or perhaps a series of more advanced, self centering jigs. This will be a demanding order for Tormek. I would guess it will sell for a much higher price and in considerably smaller quantities if Tormek decides to go forward with such a jig.

I do not see such a jig being a practical investment for the hobbiest of part time sharpener.
I would like to be wrong.

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: GKC on February 18, 2019, 05:44:39 am
I believe the final solution will be one or perhaps a series of more advanced, self centering jigs. This will be a demanding order for Tormek. I would guess it will sell for a much higher price and in considerably smaller quantities if Tormek decides to go forward with such a jig.
Ken

I think it is reasonable to expect this of Tormek, and the price should not be out of line with the rest of the equipment.  I have heard that Tormek wants to get deeper into the knife sharpening market (see the T4 Bushcraft), and it is my view that if you want to be a serious contender in this field you need to have a good self-centring jig.  Other systems have them.  The TSProf has a good self-centring jig on a rod (like a Tormek jig), I can't see why Tormek couldn't do this.

Gord
Title: Re: Long Knife Jig asymmetry problem
Post by: texaspro on February 18, 2019, 09:15:16 am
We are expecting a lot from one relatively inexpensive knife jig. We expect it to accurately grind both bevels of knives with quite a range of thicknesses and blades which are are not parallel.I think Wootz is moving in the right direction by dedicating four jigs to achieve this goal.

I believe the final solution will be one or perhaps a series of more advanced, self centering jigs. This will be a demanding order for Tormek. I would guess it will sell for a much higher price and in considerably smaller quantities if Tormek decides to go forward with such a jig.

I do not see such a jig being a practical investment for the hobbiest of part time sharpener.
I would like to be wrong.

Ken

I just wish they would figure out a way to use the jig that comes with the T-2, on the T-8. To me that is a true jig.
Title: Re: Long Knife Jig asymmetry problem
Post by: cbwx34 on February 18, 2019, 03:29:05 pm
I just wish they would figure out a way to use the jig that comes with the T-2, on the T-8. To me that is a true jig.

Herman’s Homemade Knife Rest (https://www.tormek.com/forum/index.php?topic=1592) will do this.

(A video demoing it)...  https://www.youtube.com/watch?v=AcWAkQmoU8c
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on February 19, 2019, 12:47:10 pm
I just wish they would figure out a way to use the jig that comes with the T-2, on the T-8. To me that is a true jig.

Herman’s Homemade Knife Rest (https://www.tormek.com/forum/index.php?topic=1592) will do this.

(A video demoing it)...  https://www.youtube.com/watch?v=AcWAkQmoU8c


The jig on the T2 is designed to allow restaurant staff with very little sharpening experience to sharpen most kitchen knives. Neither the T2 nor its built in jig were designed to be used by skilled sharpeners.

I agree that the homemade knife rest (Herman's small platform) works well. The T2 knife jig can be converted into a small platform, however, the conversion is expensive. Tormek does not want the T2 to be used for anything more than basic kitchen knife sharpening by kitchen staff with the built in knife jig being used conventionally.

A sharpener is much better served with a T4 or other Tormek and the traditional Tormek knife jigs. This arrangement allows a sharpener the flexibility to use his skills.

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: Darrell C on February 21, 2019, 07:22:03 am
 
Quote

Herman’s Homemade Knife Rest (https://www.tormek.com/forum/index.php?topic=1592) will do this.

(A video demoing it)...  https://www.youtube.com/watch?v=AcWAkQmoU8c

Now I like that, gotta make me one, thanks for the link..........
Title: Re: Long Knife Jig asymmetry problem
Post by: Ken S on February 21, 2019, 08:52:43 am
Don't be tempted to use the Torlock platform instead of the platform from the scissors jig. Been there; done that; the higher center of gravity does not work as well.

Every Tormek knife sharpener should have a small platform jig.

Ken
Title: Re: Long Knife Jig asymmetry problem
Post by: andrew08 on March 14, 2019, 04:37:07 pm
I generally have the right side as convexed as I can, and I even keep the shoulder on the left one on purpose in some extreme cases. But steering is a very individual matter. Get used to it, (https://www.aanmeegam.in/2019/02/mahamaham-masi-magam.html) loosen your grip and little by little you will compensate for it and need less correction of the geometry.

A good trick to see how the blade itself behaves is by making a cut without any pressure, only with the blade's weight in the inverse sense of your normal cutting. If you normally push, try this pulling and vice versa. See under which angle cuts the best.
Title: Re: Long Knife Jig asymmetry problem
Post by: smurfs on October 17, 2019, 11:09:57 pm
Apologies for resurrecting an old thread but I found this discussion on uneven bevels extremely informative and I wish to make an observation which I think is relevant which doesn't seem to have been mentioned (although it has possibly been made in another thread I've yet to read  :D).

What prompted me was the following post from texaspro...

<snip..>. I already know that my 2.5mm wide blade (Benchmade Mini Griptillian) in the SVM-45 is not the same on both sides. I am trying to figure out why and how to fix it. Unfortunately putting shims in the jig or grinding the jig down as Wootz suggests, is not applicable on 2.5mm wide blades (his method is more for under 2mm or over 3mm, from what I understand).

To be perfectly clear, the problem I am having is an uneven bevel (one side is higher than the other). No matter what I try, the angle is always different on one side as opposed to the other, causing the bevel to be higher on one side.

I can think of two scenarios where uneven bevels could occur with a perfectly centered blade, i.e 2.5mm in thickness. The first would be an uneven number of grinding passes on each side of the blade, and/or the uneven application of pressure during each pass.

It may seem obvious, but having a perfectly centered blade will not guarantee a symmetrical bevel. It also requires that refined human touch!