Tormek Community

In the Shop => Knife Sharpening => Topic started by: Jimmy R Jørgensen on July 13, 2016, 09:43:47 pm

Title: So how do i sharpen a knife like this
Post by: Jimmy R Jørgensen on July 13, 2016, 09:43:47 pm
Sorry about the erhh poor Subject name. I don't know what do call this knife edge?

How do i sharpen this on (if at all) using the Tormek??

(http://i.imgur.com/tFUCXOO.jpg)
Title: Re: So how do i sharpen a knife like this
Post by: Jan on July 13, 2016, 10:31:22 pm
Jimmy, when you will sharpen the knife on Tormek than simply use the corner of the grindstone as shown in the picture bellow.  :)

(http://img21.rajce.idnes.cz/d2102/11/11771/11771137_37021e568ec44478b9ce7dc74d286378/images/Concave_blade_700DPI.jpg?ver=0)

Jan


Title: Re: So how do i sharpen a knife like this
Post by: Jimmy R Jørgensen on July 13, 2016, 11:26:36 pm
Now that doesn't look like a easy task to do?..
Title: Re: So how do i sharpen a knife like this
Post by: Herman Trivilino on July 14, 2016, 02:28:01 am
The correct way to describe that knife is a concave edge, as opposed to the more common convex shape seen on many kitchen knives and pocket knives.

I agree that it's a very difficult proposition to sharpen such a knife. I did have a cheap paring knife shaped like that, and when it got dull I just reshaped it so the edge was straight rather than concave.
Title: Re: So how do i sharpen a knife like this
Post by: Ken S on July 14, 2016, 02:47:50 am
Jimmy,

Nice to see you posting. This bird's eye knife reminds me of the hand cut dovetails class I took with Ernie Conover. Our project was a Shaker candle box with hand cut dovetails. Most of the student boxes, mine included, looked like student work. Ernie told us not to become discouraged. If we made fifteen boxes and worked hard, we would be proficient.

You can learn to sharpen knives with concave edges. Jan has shown you the right technique. All you need to add is work and practice. I suggest starting with some knives you own.

Courage and patience, my friend!

Ken

ps to Jimmy and Jan: Very nice photographs!
Title: Re: So how do i sharpen a knife like this
Post by: Elden on July 14, 2016, 07:23:48 am

Jimmy,

Recently our local lumber yard asked me to sharpen some scissors for them. I just about refused for various reasons (we were in the process of moving and I had not done any scissors for hire for several years). But I decided  to try to help them out. There were 3 pair of scissors, 2 were offset carpet fitter's duckbill scissors similar to these:

http://www.homedepot.com/catalog/productImages/400/a9/a9bc6dbb-8fe8-4a82-81c0-5cd1016fcb41_400.jpg

Those were easily done.

The other pair was in a leather case, I did not see them until later after getting home with them. If had seen them there at the store I probably would have said I could not do them.  They are made by Buck and come apart for easy clean-up (it also made it nice for the sharpening procedure). They have a concave on one of the blades.

http://basseast.com/wp-content/uploads/2010/11/buck_shears.jpg

 The sharpening machine I used,  has a grinding wheel 12.5 mm wide. One edge of the grinding wheel has a small radius.
 
I fretted about doing them for several days before doing them. After simulating doing them several times with the machine turned off, I very lightly tried it with it turned on. By using the edge with the radius on the concave portion of the scissors blade and flattening out to the whole face for the flat portion of the blade, it went very well.

I feel that simulation runs were key in getting the movements figured out to accomplish the sharpening procedure.

Title: Re: So how do i sharpen a knife like this
Post by: Jimmy R Jørgensen on July 14, 2016, 07:42:52 am
I think that i will tell the guy the truth.. that i'm willing to give it a try, with a little help from my friends (you all). But that it is my first with concave knife edge, so the outcome is erhh unseartant.. Mayby he will say, give it a go, or maybe not.. You'll get a full update.

Thanks all.
Title: Re: So how do i sharpen a knife like this
Post by: Rob on July 14, 2016, 08:32:55 am
You can publish a photo of the court summons :-)
Title: Re: So how do i sharpen a knife like this
Post by: Jan on July 14, 2016, 09:55:47 am
Agreed, Rob. I love antiques but not such a gun shown in the picture.

Here there is an alternative picture of the same Smith & Wesson karambit knife.

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

Jan

P.S.: From my personal experience I can confirm that the concave edge is great for peeling boiled potatoes. I maintain the inside curved edge with a ceramic steel of larger diameter, because I do not want to wear off the corners of the expensive Tormek grinding wheel.
Title: Re: So how do i sharpen a knife like this
Post by: Ken S on July 14, 2016, 10:47:52 am
Jimmy,

This is a situation which proves the value of a black marker, the stone grader (graded fine), and a light touch. These will allow you to carefully monitor your progress while very slowly removing steel. As you gain experience and confidence, you can work more quickly.

When I help my granddaughter learn a new piece on the piano, she plays it very slowly, taking time to name the notes and then count. As she becomes more proficient, we increase the tempo.

Patience and persistence carries the day.

Ken
Title: Re: So how do i sharpen a knife like this
Post by: Jimmy R Jørgensen on July 14, 2016, 10:52:42 am
Thanks Ken.. belive me i will go slow.. babysteps..

As to the gun. it is softguns. but still a gun. We're not allowed to have gun in Denmark, only af few kind for hunting that's all.. it is only a few people that have guns here.
Title: Re: So how do i sharpen a knife like this
Post by: Ken S on July 14, 2016, 11:34:14 am
Jimmy,

Do an online search of "Steve Bottorff youtubes". Your time will be very productive with many well done videos, including one which specifically covers sharpening knives with inside curves.

Ken
Title: Re: So how do i sharpen a knife like this
Post by: Jan on July 14, 2016, 01:57:02 pm

As to the gun. it is softguns. but still a gun. We're not allowed to have gun in Denmark, only af few kind for hunting that's all.. it is only a few people that have guns here.

Jimmy, thanks for the clarification of the gun origin. You have calmed me down.  ;)

Jan
Title: Re: So how do i sharpen a knife like this
Post by: That Sharpening Guy on July 18, 2016, 09:47:02 pm
Jimmy, I had asked a similar question a while back so maybe some of the answers I was given may help.

Good luck!!

http://www.tormek.com/forum/index.php?topic=2407.msg11995#msg11995
Title: Re: So how do i sharpen a knife like this
Post by: Jan on July 19, 2016, 09:07:00 am
Good reminder, TSG!  :)

Your wave shaped karambit knife was surely much more difficult to sharpen because of the double curved blade and also the more pronounced blade concaveness. Some sharpeners understand the second blade curve as a large serration.

What is your current procedure to sharpen such a knives?

Jan
Title: Re: So how do i sharpen a knife like this
Post by: wootz on July 21, 2016, 08:38:22 am
I tried to word the procedure I follow myself for sharpening concave blades on Tormek.
Feel free to ask if unclear in any part.

Knives I sharpen using the below procedure.
(http://home.exetel.com.au/dropbox/Concave_knives.JPG)

The stone must be graded fine and the stone corner must be smoothed out, just a little.
(http://home.exetel.com.au/dropbox/Concave_stone.JPG)

Grind away from the edge.
Set grinding angle at the concave trough, with the jig adjustable stop pressed against the Universal Support.
Mark the line of contact (LOC) with a laser.
Lock collar at the ends of the concave (crests), with the collar pressed against the Universal Support.
(http://home.exetel.com.au/dropbox/Concave_sharpening.JPG)

The concave is sharpened near the edge of the stone on the side of the handle.
E.g. with tip pointing to you right, sharpen near the left stone edge area ~5mm wide.

1.
Start at the bolster end of the concave (crest), i.e. with the locked collar pressed against the Universal Support, positioning the blade at the point where the laser LOC crosses the stone edge, and tilting the blade just enough not to touch the stone with the rest of the blade.

Do the descending part moving the jig with lateral and forward movement, maitaining the blade contact with the stone at the LOC crossing the stone edge, and not tilting unnecessarily.
E.g. with tip pointing to you right, move the jig left-and-forward; maintain the jig position perpendicular to the Universal Support.

2.
Do the trough segment with the jig adjustable stop pressed against the Universal Support.

3.
Then continue to the ascending part, moving the jig with lateral and backward movement.
At the end of the ascending part you reach the locked collar.

These steps are illustrated on the next 3 photos.
(http://home.exetel.com.au/dropbox/Concave_1.JPG)
(http://home.exetel.com.au/dropbox/Concave_2.JPG)
(http://home.exetel.com.au/dropbox/Concave_3.JPG)

Similarly sharpen the other side of the blade on the opposite stone corner.

Hone on a tapered felt wheel with 0.5 micron diamond paste.
(http://home.exetel.com.au/dropbox/Concave_honing.JPG)
Title: Re: So how do i sharpen a knife like this
Post by: Jan on July 21, 2016, 01:17:23 pm
Wootz, thanks for posting a detailed description of your procedure for sharpening concave blades.  :)
I was also pleased to read that you are using a laser line.  :)

I would like to ask you how much you charge for a single concave blade sharpening. In my opinion, the preparation of the rounded edge of the grinding wheel and subsequent truing is quite a costly affair. I assume that the rounding and truing procedure will cost you at least 2 mm of grindstone diameter which represents more than 2% of its total capacity.  :-\

It would be good to have one grindstone dedicated to this work. Do you think that a worn grindstone would it be appropriate for this purpose?  :-\

Jan
Title: Re: So how do i sharpen a knife like this
Post by: wootz on July 22, 2016, 08:25:46 am
Hi Jan, haven't spoken with you for long.
You guess right, I have two alumina SG stones, one with square corners, and another with rounded. This covers all knife shapes, the rest is technique.
What to charge depends both on the time and consumables spent; to sharpen a short karambit like pictured might cost more than an 8" kitchen knife only because the karambit takes longer to set up.

Title: Re: So how do i sharpen a knife like this
Post by: Jan on July 22, 2016, 05:16:13 pm
Wootz, thanks for your clarification!  :)

Jan
Title: Re: So how do i sharpen a knife like this
Post by: WolfY on July 23, 2016, 02:27:51 pm
Just yesterday as I was demonstrating and sharpening at a knife and cold weapon fair, and had some queries for shaping and sharpening concave blades. I tried to avoid it as I knew I have to use the edge of the stone and didn't want to round it. And today I see this post :)

So, after lots of thinking about the necessity of it my q. is: Is it really necessary to have a straight 90 dgrs edge for knife sharpening, for ex. or the rounded edge don't make a different, leaving the necessity of either truing (not an option) the stone or having 2 stones. I even think it will be an advantage to have it rounded always.

The other thing I noticed is the use of laser line marker. Can you pls, show and explain how you added it to the machine?

Thanks in advance
Title: Re: So how do i sharpen a knife like this
Post by: SharpenADullWitt on July 23, 2016, 03:43:19 pm
Won't having rounded corners, just make the stone narrower? (for sharpening purposes)
Trying to remember what JF said about minimum stone size.  Because I am thinking that maybe one could make a spacer and use a T-4 wheel, with rounded corners on the T-7 and the spacer could give clearance on both sides of the wheels, for unusual profile knives. ???
Title: Re: So how do i sharpen a knife like this
Post by: Jan on July 23, 2016, 06:10:01 pm
Just yesterday as I was demonstrating and sharpening at a knife and cold weapon fair, and had some queries for shaping and sharpening concave blades. I tried to avoid it as I knew I have to use the edge of the stone and didn't want to round it. And today I see this post :)

So, after lots of thinking about the necessity of it my q. is: Is it really necessary to have a straight 90 dgrs edge for knife sharpening, for ex. or the rounded edge don't make a different, leaving the necessity of either truing (not an option) the stone or having 2 stones. I even think it will be an advantage to have it rounded always.

The other thing I noticed is the use of laser line marker. Can you pls, show and explain how you added it to the machine?

Thanks in advance

Wolfy,
Ad1) Having the stone corners rounded you cannot sharpen the edge near the handle.  ;)

Ad2) Laser line is a battery powered laser line module mounted on a bar which can be attached to Tormek housing e.g. via the USB sleeve. It is good for freehand sharpening, belly sharpening, platform sharpening and in many other situations.
 
(http://img21.rajce.idnes.cz/d2103/11/11709/11709430_28620584321cb814b04ba1648f79a5d3/images/LASER_LINE_1_640DPI.jpg?ver=0)

For more info read
http://www.tormek.com/forum/index.php?topic=2562.135


 Jan
Title: Re: So how do i sharpen a knife like this
Post by: WolfY on July 23, 2016, 09:28:39 pm
Ad1) Having the stone corners rounded you cannot sharpen the edge near the handle.  ;)
Of course losing 3 mm of the corner will decrease the sharpening area and the ability to fully get close to the start/ end point of sharpening near the handle. Normally it's not a problem for me as I don't sharpen the closest 5mm near the handle for user safeness :)

Ad2) Laser line is a battery powered laser line module mounted on a bar which can be attached to Tormek housing e.g. via the USB sleeve. It is good for freehand sharpening, belly sharpening, platform sharpening and in many other situations.

I have other thoughts of use this kind of attachment. Not for freehand sharpening purpose.
Can you provide a link to where I can get one of those?

Thanks.
Title: Re: So how do i sharpen a knife like this
Post by: Jan on July 23, 2016, 09:38:11 pm
Wolfy, the laser line shown is my homemade prototype. Your interest may inspire some manufacturer.  :)

Jan
Title: Re: So how do i sharpen a knife like this
Post by: WolfY on July 23, 2016, 09:41:26 pm
Wolfy, the laser line shown is my homemade prototype. Your interest may inspire some manufacturer.  :)

Startup :) Kickstarter?
I'm signing up for one. Just name the price ;)
Title: Re: So how do i sharpen a knife like this
Post by: wootz on July 23, 2016, 09:58:21 pm
I use this laser I sourced from eBay, cost me US$ 9.50 delivered
http://www.ebay.com/itm/Industrial-650nm-5mW-focusable-Red-Laser-Line-Diode-Module-w-AC-Adapter-13x42mm-/131790206137?hash=item1eaf4ef4b9:g:SyYAAOSw1DtXGuNH (http://www.ebay.com/itm/Industrial-650nm-5mW-focusable-Red-Laser-Line-Diode-Module-w-AC-Adapter-13x42mm-/131790206137?hash=item1eaf4ef4b9:g:SyYAAOSw1DtXGuNH)

Unlike Jan, I didn't attach it to the Tormek, but have it on a separate stand next to it.

Laser marking of the line of contact helps to properly do concave, pronounced convex and S-shaped blades.
But the locking collar is not as necessary, it's just an additional reference point aiding with a complex shape.

So grateful to this forum for this laser LOC idea. If I remember right, Ken first suggested it, and Jan realised.
Title: Re: So how do i sharpen a knife like this
Post by: RichColvin on July 25, 2016, 01:44:17 pm
Won't having rounded corners, just make the stone narrower? (for sharpening purposes)
Trying to remember what JF said about minimum stone size.  Because I am thinking that maybe one could make a spacer and use a T-4 wheel, with rounded corners on the T-7 and the spacer could give clearance on both sides of the wheels, for unusual profile knives. ???

I recently listened to a Fine Woodworking podcast where they discussed the advantages of rounding the surface of the grinding wheel.  They advocate that this makes sharpening easier & faster. 
Title: Re: So how do i sharpen a knife like this
Post by: Ken S on July 25, 2016, 08:23:45 pm
Rich,

I believe the podcast goes back to one of the Isles family of toolmakers. He puts a crown on his (dry) grinding wheels to minimize the contact area during grinding to keep the tool cooler. I will check. I printed the article. I believe it was on Tools for Working Wood. Here is the link. It is well worth your time for dry grinders.

http://www.toolsforworkingwood.com/store/blog/453/title/Further+Thoughts+On+Grinding

Ken
Title: Re: So how do i sharpen a knife like this
Post by: RickKrung on October 01, 2017, 05:11:45 am
Disregard this post.  Had a question about how to power it, but found one that has the power adapter, so order it. 

Rick
Title: Re: So how do i sharpen a knife like this
Post by: Ken S on October 02, 2017, 03:53:53 am
I recall a post where Jeff Farris, the founder of this forum and a very experienced Tormek user, stated that he had ground a small radius into the inside corner of his grinding wheel.

Ken
Title: Re: So how do i sharpen a knife like this
Post by: cbwx34 on October 02, 2017, 02:35:39 pm
I always knock the sharp edge off of the wheel (both sides, not just one)... sharpening stones too.