Advice for these Blades

[JKeetonKnives]

I'm a custom knife maker and I have a few knife styles that I was looking for advice on how to sharpen. They both have fairly aggressive curves towards the tip in the direction of the spine.





When using the "handle raising method" and keeping the jig perpendicular to the guide; the tip bevel moves "up the wheel" towards the user. Which results in a different tip bevel angle.

Like this:





I found this old thread on a jig, but I'm afraid it will scratch my finish:

https://forum.tormek.com/index.php?topic=1592


I also found these collar stops:



Does anyone use these type of jigs? You have to pivot correct? Seems pretty difficult. But I'm game if that's what it takes.

Thanks for any help!
JKeeton

[wootz]

The thread you need is just a few downwards: https://forum.tormek.com/index.php?topic=3780.0

Yes, you need to pivot, and need a pivoting adapter of a sort on your knife jig as pivoting the stock Tormek knife jig will not grind even bevels.
See if you can make one yourself, similar in functionality to the Pin Pivot Collar described in the above thread.

[JKeetonKnives]

The thread you need is just a few downwards: https://forum.tormek.com/index.php?topic=3780.0

Yes, you need to pivot, and need a pivoting adapter of a sort on your knife jig as pivoting the stock Tormek knife jig will not grind even bevels.
See if you can make one yourself, similar in functionality to the Pin Pivot Collar described in the above thread.

Excellent, thank you very much! I missed that one. Cool jig for sure!

[JKeetonKnives]

After looking at it, I think I'm going to try to replicate this jig, however, I'm going to go a little simpler.

I was thinking of drilling a hole in the stem of the knife jig and inserting a pin, and then have a set screw @90 degrees. Very cool jig. Hope it works!

[JKeetonKnives]

Like this (can't wait to try it):



I peined over the holes a little to give a tight fit as a temporary solution. If I never take it off, I'll go back and epoxy it in with some G-Flex.

Cheers,
JKeeton

[RichColvin]

James,

The difficulty with your approach is that it doesn't allow for moving the pin to adjust the projection.  Such movement is needed to account for different size blades.

Rich

[JKeetonKnives]

Hey Rich, can't this be accomplished by raising and lowering the tooling arm till the appropriate secondary bevel angle is achieved?

[Elden]

Couple of previous ideas.

https://forum.tormek.com/index.php?topic=3802.msg25365#msg25365

https://forum.tormek.com/index.php?topic=3957.msg26950#msg26950

[JKeetonKnives]

Couple of previous ideas.

https://forum.tormek.com/index.php?topic=3802.msg25365#msg25365

https://forum.tormek.com/index.php?topic=3957.msg26950#msg26950

Wow those are sweet! Thanks so much for sharing those. I really like the triangular one. Great design.

[Jan]

Hey Rich, can't this be accomplished by raising and lowering the tooling arm till the appropriate secondary bevel angle is achieved?

Generally it is better to have two degrees of freedom, the USB height and the protrusion length. Nevertheless the USB height is sufficient to set the desired bevel angle provided that the protrusion is not too short.

Jan

[Ken S]

Hey Rich, can't this be accomplished by raising and lowering the tooling arm till the appropriate secondary bevel angle is achieved?

Generally it is better to have two degrees of freedom, the USB height and the protrusion length. Nevertheless the USB height is sufficient to set the desired bevel angle provided that the protrusion is not too short.

Jan

Jan expresses this very well. I use capital letters, Projection and Distance to denote the two variables. I like having the freedom to work with either or both. Part of this freedom is standardization. I found that using a Projection of 139mm falls in the middle of the adjustment range for chef's knives, slicing knives, and paring knives (when the SVM-00 is used with paring knives). I use separate preset jigs for the three sizes of knives. This means I rarely have to make even small adjustments when changing knives of different sizes. Using Dutchman's grinding angle tables, my Distance from the support bar
to the grinding wheel will be 80mm, for a 15° bevel angle with a 250mm wheel. The Knife Grinders applet also calculates in the FVB setting. The end result is essentially the same, the variables can be standardized; no individual measurement is necessary. This is an important time saver when one has many knives to sharpen in a short time.

Ken

[John_B]

I like having the fine adjustment when I am using the Sharpie method to exactly duplicate an existing angle. I have a couple of customers that specifically ask for the knife to be sharpened at the exact angle it is currently at. Without the laser tool to accurately measure the angle the sharpie is all I have at my disposal.

[RichColvin]

The aluminium block idea from Gord Cameron (GKC on the forum) is a really good one that is very cost effective.  It also allows the sharpener to adjust the projection.  The reason is that the generally accepted projection target is 139 mm.  I've adopted the idea of a block of wood, screwed to a base with a set the projection at 139mm, and this makes it easy for me.

That projection can be different, but it sets one of the variables.  And all the pivot ideas I've seen (http://sharpeninghandbook.info/indexJigs.html#PivotJig ) are designed around the idea of moving it in or out on the SVM knife jig.

Once this is set, fine adjustment is done via the nut on universal support bar. 

The terms and math for calculating this are here :

http://sharpeninghandbook.info/indexCalcProjDetails.html

If you go the route of using a front vertical base (FVB), then KnifeGrinder's calculator is quite useful. 

Good luck,
Rich

[JKeetonKnives]

Good luck,
Rich

Hey Rich, thanks for this explanation.

[JKeetonKnives]

Way better results with my modified jig than with the hand raise method alone. I think the combination of this jig and the handle raise method get me pretty damn close.

Thanks for the help!