Author Topic: Long Knife Jig asymmetry problem  (Read 33493 times)

Offline Skitz

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Re: Long Knife Jig asymmetry problem
« Reply #90 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


Offline cbwx34

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Re: Long Knife Jig asymmetry problem
« Reply #91 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.
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Offline RichColvin

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Re: Long Knife Jig asymmetry problem
« Reply #92 on: February 12, 2019, 05:13:58 pm »
CB is right :  I use them all on my SuperGrind 2000.

Kind regards,
Rich
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Offline texaspro

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Re: Long Knife Jig asymmetry problem
« Reply #93 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"??


Offline texaspro

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Re: Long Knife Jig asymmetry problem
« Reply #94 on: February 13, 2019, 03:19:05 pm »
other side

Offline RickKrung

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Re: Long Knife Jig asymmetry problem
« Reply #95 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
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Offline texaspro

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Re: Long Knife Jig asymmetry problem
« Reply #96 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.

Offline texaspro

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Re: Long Knife Jig asymmetry problem
« Reply #97 on: February 13, 2019, 06:37:40 pm »
This is a crude representation of what the bevel looks like from the side.

Offline texaspro

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Re: Long Knife Jig asymmetry problem
« Reply #98 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 😎

Offline cbwx34

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Re: Long Knife Jig asymmetry problem
« Reply #99 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...



... 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?
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Offline texaspro

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Re: Long Knife Jig asymmetry problem
« Reply #100 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.

Offline texaspro

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Re: Long Knife Jig asymmetry problem
« Reply #101 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

Offline cbwx34

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Re: Long Knife Jig asymmetry problem
« Reply #102 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...



... at any rate, glad you got it figured out!
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Offline texaspro

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Re: Long Knife Jig asymmetry problem
« Reply #103 on: February 15, 2019, 04:04:37 am »
Ah, that makes sense...

Offline RickKrung

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Re: Long Knife Jig asymmetry problem
« Reply #104 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)


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
« Last Edit: February 15, 2019, 06:29:31 am by RickKrung »
Quality is like buying oats.  If you want nice clean, fresh oats, you must pay a fair price. However, if you can be satisfied with oats that have already been through the horse, that comes at a lower price.