Clamp of the week... (or try something different)...

[GKC]

Rick, I will be able to report soon on the Hewn & Hone self-centering jig (designed for Tormek and similar machines).  It has obvious blade size limitations because it was designed specifically for scandi grinds on thin carving knives, but it might provide you with some ideas or parameters for your own design.

Gord

[RickKrung]

Rick, I will be able to report soon on the Hewn & Hone self-centering jig (designed for Tormek and similar machines).  It has obvious blade size limitations because it was designed specifically for scandi grinds on thin carving knives, but it might provide you with some ideas or parameters for your own design.

Gord

Gord,

Just seeing the picture is a big help.  What would help further are some dimensions.  You could PM them so as to not clutter the forum. 

I've shifted my design efforts back to modifying an existing knife jig (SVM-45), which may take significant modification, in which case it may be better for me to use the design principles of interest from it and start from scratch. 

One feature I may go with is the use of Heli-Coil type stainless steel threaded inserts.  I found some locally that are M6x1 so I can use the Tormek screws, which I really like.  These would make starting from scratch more feasible. 

Thanks,

Rick

[Ken S]

I am the odd man when it comes to knife jigs. My knives, both kitchen and pocket knives, generally have very mild curves. I have thought about modifying the jig to eliminate the radius, thus relying on lifting the blade for the tip.I also use several jigs to minimize or eliminate the need to adjust jig length. Therefore, I would be happy eith a finer thread.

I don't expect Tormek to redesign the knife jigs just for me, although if I was a weekend warrior, I would have some custom machining work done.

Ken

[RickKrung]

...snip... I have thought about modifying the jig to eliminate the radius, thus relying on lifting the blade for the tip.

Ken, I am not following this.  What radius would you eliminate and why can you not already rely solely on lifting for the very mild curves of your knives?

I also use several jigs to minimize or eliminate the need to adjust jig length. Therefore, I would be happy eith a finer thread. ...snip...

Not following this either.  Finer thread of what?  If you have multiple jigs, each set at different projections (I'm assuming this) that you hardly ever change, why would the pitch of the thread (of the stop) matter? 

Rick

[Ken S]

Rick,

I would eliminate the radius on the adjustable stop. Actually, this would probably mean having two adjustable stops, one specifically designed for fairly straight blades and one for more curved blades. This bothered me more years ago; I may have outgrown the need for it.

I guess the shaft thread does not matter. As I rarely adjust more than a small amount (and much of the time require no adjustment at all) adjustment speed is of no importance to me. I would prefer fine adjustment. I realize that is a minority opinion.

The jig is essentially well designed, although I believe it can be improved.

Ken

[Ken S]

Rick,

The SVS-50 Multi Jig is designed to include radiused skews. It has a flat bearing surface against the support bar.

The scissors jig has no radius surface, even though scissors often have some radius.

Why do we need a radius on the adjustable stop of the knife jig for knives with little curve? (I think the Tormek plan is for a "universal", one size fits all adjustable stop. I propose that a dedicated flat adjustable stop for straighter blades would work better.)

Ken

[GKC]

OK Ken, I wasn't going to post about this idea, but...

A few of your points about eliminating the rounded edge on the adjustable stop, and having one stop for straight blades and a separate one for curved, prompt me to post these pictures of a "concept jig" I made to go on the knife jigs, for reasons similar to those you mention. 

It had occurred to me that you could have both the "keep it straight" support of a flat surface bearing on the USB (the evident purpose of the wide collar on the current Tormek stop), and the ability to pivot with complete freedom (and without changing the radius/projection) when you came to the curve.  All in one jig.

It is shaped like the prop of an airplane, so I called it a "prop collar".  The "blades" are 1/8" aluminium mounted (JB Weld) on a stop collar (tightens with a grub screw).

Going in each direction, the flat blade of the prop holds you straight, then you can pivot when you reach the curved section of the blade.  (the pivot point, if you want to pivot, is exactly in the centre of the collar.)  Then you flip over and do the other side, as you do normally.  It even gives you decent support if you are lifting, or pivoting and lifting.

Though I only made this prototype to test the concept, I have tried it and it really works, you just have to get the feel for the direction you are going, and develop some muscle memory.  Keep it flat against the USB for full control as you are sharpening the straight section, then pivot as much as you want once you come to the curve.  Flip and repeat.

Gord

[Ken S]

Gord,

This looks intriguing. I will examine it further in the morning when my brain is more awake,

Ken

[cbwx34]

...
It had occurred to me that you could have both the "keep it straight" support of a flat surface bearing on the USB (the evident purpose of the wide collar on the current Tormek stop), and the ability to pivot with complete freedom (and without changing the radius/projection) when you came to the curve.  All in one jig.

It is shaped like the prop of an airplane, so I called it a "prop collar".  The "blades" are 1/8" aluminium mounted (JB Weld) on a stop collar (tightens with a grub screw).

Going in each direction, the flat blade of the prop holds you straight, then you can pivot when you reach the curved section of the blade.  (the pivot point, if you want to pivot, is exactly in the centre of the collar.)  Then you flip over and do the other side, as you do normally.  It even gives you decent support if you are lifting, or pivoting and lifting.

Though I only made this prototype to test the concept, I have tried it and it really works, you just have to get the feel for the direction you are going, and develop some muscle memory.  Keep it flat against the USB for full control as you are sharpening the straight section, then pivot as much as you want once you come to the curve.  Flip and repeat.

Gord

Although I don't think keeping the straight part straight is that big an issue, (for most knives anyway)... I admire the creativity of your solution.  Pretty cool! (and an appropriate post for this thread).   I do understand the design... the desire to have both a pivot and flat in one jig is a good idea.  👍👍

[cbwx34]

...
The SVS-50 Multi Jig is designed to include radiused skews. It has a flat bearing surface against the support bar.

The scissors jig has no radius surface, even though scissors often have some radius.

Why do we need a radius on the adjustable stop of the knife jig for knives with little curve? (I think the Tormek plan is for a "universal", one size fits all adjustable stop. I propose that a dedicated flat adjustable stop for straighter blades would work better.)

Ken

I"ve never used the SVS-50... so I'll just quote from the book.  You can put a curved edge on a skew... you pivot the jig with the tool on the universal support...



... so it is not always used "flat".

The scissors jig is essentially a platform jig, with the clamped scissors riding on a platform, so it also is not "flat"... and can follow a curve?   (BTW, if a person doesn't believe in "pivot" vs. "lift"... doesn't the platform jig rely entirely on the former?)

...
I would eliminate the radius on the adjustable stop. Actually, this would probably mean having two adjustable stops, one specifically designed for fairly straight blades and one for more curved blades. This bothered me more years ago; I may have outgrown the need for it.
...

I'm curious... how much "flat" do you need in a jig to keep the knife jig flat against the USB?  The standard jig seems to have plenty of flat surface... I don't understand the desire to eliminate the radius... just don't use it?  Realllly not getting this...   

[Ken S]

My first exposure to sharpening knives with the Tormek was from watching Jeff Farris' video. Jeff explained that the way to sharpen the tip of the knife was to lift the handle of the knife, not rotate the knife. I found the radius on the adjustable stop a constraint for the standad kitchen knives I sharpen. While the radius may be useful for more curved shapes, I would have preferred a flatter surface for my knives.

In the long run, I believe an ideal knife jig would have more than one easily interchangeable adjustable stopd.

Ken

[sharpening_weasel]

Regarding self centering clamp- I've seen something like this used in a machinist's shop before. It's a relatively simple mechanism- two opposite thread pitches guide a ram along two exterior rails. If we could figure out a way to miniaturize this, and perhaps recess and angle the jaws so they don't interfere, I think we would be set. The problem would be ensuring the mechanism doesn't get in the way of the stone.

https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.spreitzer.de%2Fen%2Fclamping-technology%2Fcentre-clamping-vises%2F&psig=AOvVaw3Rbg-rf8IDQ8XefezsU019&ust=1611008691047000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCIjUgKSBpO4CFQAAAAAdAAAAABAD

Extrapolating from this setup, something along these lines would be might be simpler. The black bit remains exactly in the middle at all times. If we attach the post to the rear of the equivalent black bit, and cut reliefs in the jaws, I think this could very well work. A friend of mine is a machinist, but I'm afraid I have just about zero budget right now (t8 and KG purchases.) Anyway that's my very amateur two bits.