How can we jig this short & curved blade?

[Sharpco]

This is CRKT Squid that has a short & curved blade.

As a result of sharpening with the SVM-45, the angle of the tip increased significantly.

Is there a way to solve this?

[wootz]

You can ask Rick Kruger if he has got one of his Pivot Collars for you - they are designed to help with this, and as far as I know he may have a couple of them spare right now.
The Pivot Collar is put on the Tormek knife jig und used instead of the adjustable stop; when you don't need it, you can remove it.

Pictured is an initial design, in the last version you just remove the adjustable stop when and use the Pivot Collar instead.





more details here:
https://forum.tormek.com/index.php?topic=3459.75

[cbwx34]

This is CRKT Squid that has a short & curved blade.

As a result of sharpening with the SVM-45, the angle of the tip increased significantly.

Is there a way to solve this?

Technically, that blade at 54mm is too short for the SVM-45... its min. recommended blade length is 60mm.

But, this is where having a pivot point comes in handy.  As wootz posted, the pivot collar, or even cutting down the stock collar is part of the solution... but not the entire answer.

Since the blade is so short, the other part is to clamp it at an angle (to get the clamp out of the way).  Since you're now rotating on a point, it makes it easy to follow the shape of just about any blade.

I don't have that particular knife, but I have a CRKT with a similar shape... so I "shortened" it, by clamping it closer to the tip...




... clamping it "straight" I still might have had problems to sharpen it properly, but angling the knife allowed me to set it so that it stayed on the same line on the wheel.  (Like I posted somewhere else, draw a line across the wheel, and set the blade so that it stays on, (or as close as possible to), the line as you sharpen from heel to tip.  This allowed me to properly sharpen the knife, keeping a consistent bevel from heel to tip...



Also, an alternative for some blades, is to use the "Small Knife Holder" (SVM-00), and clamp it on the handle...



... this will allow you to clamp the blade farther back, and should give you enough length you'll be able to do a "pivot & lift" technique to better follow the bevel with the standard stop collar.

[RickKrung]

You can ask Rick Kruger if he has got one of his Pivot Collars for you - they are designed to help with this, and as far as I know he may have a couple of them spare right now.
The Pivot Collar is put on the Tormek knife jig und used instead of the adjustable stop; when you don't need it, you can remove it.
...snip...
more details here:
https://forum.tormek.com/index.php?topic=3459.75

I do have a few, but have not sent them out to anyone yet.  I haven't really done much testing with them yet and only recently got a few of them welded rather than Loc-Tited.  As Wootz mentioned, the design has changed, from a collar that is secured with a set-screw that benefited greatly with a flat milled in the side of the jig shaft (SVM-45).  The new design uses a clamping collar, thanks to CB and Wootz's suggestions.  Much more positive locking and no possibility of marring the shaft and no need for milling a flat.

First is an image of the welded pin pivot clamp collar (PPCC).


Second shows it clamped on a knife jig (SVM-45) shaft.


Third is an assortment, showing the cut down stock adjustable stops that I use behind the PPCC, to some extent as an aid in positioning, but more so there is something more comfortable and substantial behind the PPCC to grip while holding it on the USB.  This shows the Schrader blade clamped in the jig.  Technically, this knife is also too short for the SVM-45, at a length of 50mm (why do they call it "45" if that is smaller than the nominal knife blade length capacity?). 


PPCC on the jig shaft showing how it rests on the USB.


And then, on the T8, set for 15º bevel angle, using Wootz's applet. 


Rick

[RickKrung]

Here is how sharpening that Schrader 50mm blade went.  I started with the SB stone set at 15º bevel angle.  After re-reading the extensive thread on whether to "Pivot or Lift", and looking at some of the referenced links, I finally got it about lifting the blade as you work up the curve to the tip. 

After grinding the blade on the SB, and coming up with a fairly nice even bevel (no pic of it), I tried to set up the leather honing wheel for the angle, but blew it badly, setting much to low of an angle.  After working up to an angle close to 15º, I messed up the edge by over-honing it. 

I recently bought a dissecting microscope with a magnification range from 3.5X-90X.  I justified/rationalized it as a fun tool for showing my 4-yr old granddaughter the micro world, which she has already been thrilled with.  (Did you know bees have hair on their backs?).  As a fish biologist when I was a working stiff and a fly fisherman, I know lots of things to show her.  I also had in mind examining knife edges. 

Well, I looked at the grind pattern (scratches really) and the edge condition.  Not pretty.  So, I decided to try the SJ stone for the first time, to see how it works refining the scratch pattern and to see if it could salvage the edge.  It did a great job of significantly refining the scratches, but I was not able, yet, to repair the botched honing on the edge. 

Two photos showing the bevel and edge.  The camera I got with the microscope (3MP) is not good enough to get the kind of images I want and there is no focusing ability on the trinocular, which is where the camera mounts.  So, it is a trial and error job of getting the camera in focus on the same plane as the oculars.  I have already drafted a design for adding a fine focusing feature for the trinocular.  Waiting for materials and a tap.  I also have a much better camera on order (18MP).

I do not know what magnification these are actually at, but it is clear the grind/scratch pattern is very fine.  What I do know is I was somewhere withing the primary magnification range of the 3.5X objective. 


The fine dark line along the top edge is the remnant of the botched honing job. 


Three photos of the finished sharpening, as it stands now.  I want to go back later to work out the last of the poor honing job.  This is, however, the best job of sharpening I have accomplished so far, at least as far as uniformity of the bevel width at the same time as maintaining the same bevel angle. 







I did notice for the first time, the asymmetry of the bevel width, I believe due to the blade not being centered in the jig, as has been discussed elsewhere.  From prodding CB, I am working on a design to address that asymmetry.

Rick

[cbwx34]

...this knife is also too short for the SVM-45, at a length of 50mm (why do they call it "45" if that is smaller than the nominal knife blade length capacity?).

The clamp is 45mm across.

First is an image of the welded pin pivot clamp collar (PPCC).

Lookin' good!!! 

[Sharpco]

You can ask Rick Kruger if he has got one of his Pivot Collars for you - they are designed to help with this, and as far as I know he may have a couple of them spare right now.
The Pivot Collar is put on the Tormek knife jig und used instead of the adjustable stop; when you don't need it, you can remove it.

Pictured is an initial design, in the last version you just remove the adjustable stop when and use the Pivot Collar instead.





more details here:
https://forum.tormek.com/index.php?topic=3459.75

The idea of Rick Kruger is wonderful.

If you need to sharpen a squid-like knife, how can you solve this problem without Rick Kruger's jig?

[Sharpco]

This is CRKT Squid that has a short & curved blade.

As a result of sharpening with the SVM-45, the angle of the tip increased significantly.

Is there a way to solve this?

Technically, that blade at 54mm is too short for the SVM-45... its min. recommended blade length is 60mm.

But, this is where having a pivot point comes in handy.  As wootz posted, the pivot collar, or even cutting down the stock collar is part of the solution... but not the entire answer.

Since the blade is so short, the other part is to clamp it at an angle (to get the clamp out of the way).  Since you're now rotating on a point, it makes it easy to follow the shape of just about any blade.

I don't have that particular knife, but I have a CRKT with a similar shape... so I "shortened" it, by clamping it closer to the tip...




... clamping it "straight" I still might have had problems to sharpen it properly, but angling the knife allowed me to set it so that it stayed on the same line on the wheel.  (Like I posted somewhere else, draw a line across the wheel, and set the blade so that it stays on, (or as close as possible to), the line as you sharpen from heel to tip.  This allowed me to properly sharpen the knife, keeping a consistent bevel from heel to tip...



Also, an alternative for some blades, is to use the "Small Knife Holder" (SVM-00), and clamp it on the handle...



... this will allow you to clamp the blade farther back, and should give you enough length you'll be able to do a "pivot & lift" technique to better follow the bevel with the standard stop collar.

Good idea.

I would like Tormek to design a new knife jig, or make an additional jig to solve this situation. But it's hard to anticipate it, so it would be nice to make a "Stop" that can be replaced for pivoting.

[Sharpco]

You can ask Rick Kruger if he has got one of his Pivot Collars for you - they are designed to help with this, and as far as I know he may have a couple of them spare right now.
The Pivot Collar is put on the Tormek knife jig und used instead of the adjustable stop; when you don't need it, you can remove it.
...snip...
more details here:
https://forum.tormek.com/index.php?topic=3459.75

I do have a few, but have not sent them out to anyone yet.  I haven't really done much testing with them yet and only recently got a few of them welded rather than Loc-Tited.  As Wootz mentioned, the design has changed, from a collar that is secured with a set-screw that benefited greatly with a flat milled in the side of the jig shaft (SVM-45).  The new design uses a clamping collar, thanks to CB and Wootz's suggestions.  Much more positive locking and no possibility of marring the shaft and no need for milling a flat.

First is an image of the welded pin pivot clamp collar (PPCC).


Second shows it clamped on a knife jig (SVM-45) shaft.


Third is an assortment, showing the cut down stock adjustable stops that I use behind the PPCC, to some extent as an aid in positioning, but more so there is something more comfortable and substantial behind the PPCC to grip while holding it on the USB.  This shows the Schrader blade clamped in the jig.  Technically, this knife is also too short for the SVM-45, at a length of 50mm (why do they call it "45" if that is smaller than the nominal knife blade length capacity?). 


PPCC on the jig shaft showing how it rests on the USB.


And then, on the T8, set for 15º bevel angle, using Wootz's applet. 


Rick

Good job!

[cbwx34]

The idea of Rick Kruger is wonderful.

If you need to sharpen a squid-like knife, how can you solve this problem without Rick Kruger's jig?

Actually, overlooked the obvious.  You can sharpen the knife without any jig... freehand sharpen it.

Short knives are easier to do this way... since you don't have to move your hands much, you can use the USB as a rest/guide for you hands... to help hold the angle, and consistent spot on the stone.  (Best done on the horizontal USB).

Another option to consider!

[RickKrung]

The idea of Rick Kruger is wonderful.

If you need to sharpen a squid-like knife, how can you solve this problem without Rick Kruger's jig?

Actually, overlooked the obvious.  You can sharpen the knife without any jig... freehand sharpen it.

Short knives are easier to do this way... since you don't have to move your hands much, you can use the USB as a rest/guide for you hands... to help hold the angle, and consistent spot on the stone.  (Best done on the horizontal USB).

Another option to consider!

Or you could find yourself a source for a 12mm ID collar and use it in place of the stock adjustable collar.  I believe CB was the first one I saw (he posted here about it).  I get mine from McMaster-Carr, but they come in packs of 10 and cost over $100 for the pack. 


A piece of some kind of tubing, rubber, PVC or whatever, slit down the length so it can compress, compressed with a hose clamp might work.  Ya gotta get a bit ingenious. 

[RickKrung]

A piece of some kind of tubing, rubber, PVC or whatever, slit down the length so it can compress, compressed with a hose clamp might work.  Ya gotta get a bit ingenious.

Here is a solution that anyone should be able to do, if they have some very basic tools. 

Here is what it took:

Cordless (or corded) drill
1/2" drill bit

From a hardware store:
1/2" x 1/4" PVC (MIPxFIP) pipe fitting reducer

Blue painters tape (or any kind of masking type tape).

Drill out the the pipe fitting using the 1/2" drill.
Wrap the SVM-45 shaft with enough tape to make the pipe fitting a snug but turnable fit. 

Adjust to the projection distance you want for the knife.

Done

20 minutes. 

[cbwx34]

Or you could find yourself a source for a 12mm ID collar and use it in place of the stock adjustable collar.  I believe CB was the first one I saw (he posted here about it).  I get mine from McMaster-Carr, but they come in packs of 10 and cost over $100 for the pack. 

A piece of some kind of tubing, rubber, PVC or whatever, slit down the length so it can compress, compressed with a hose clamp might work.  Ya gotta get a bit ingenious.

The Stop Collar I got, also from McMaster Carr, can be bought individually, and can be found HERE.  Not as fancy as Rick's version, but does the job.

I agree with Rick.... just about anything to reduce the pivot point down should work... although it needs to be able to slide along the USB.  Another alternative is to just remove the Stop Collar... basically becomes a "guided freehand" setup... but you need a way to insure you stay on the same line on the wheel.  (Where the laser comes in).   

[RickKrung]

...snip...
I agree with Rick.... just about anything to reduce the pivot point down should work... although it needs to be able to slide along the USB.  ...snip...

I would modify this to "it has to be movable (as in sliding or rotating or pushed) along the shaft and be position-able with a fairly positive stop/locking method. 

Rick

[Stickan]

Hi,
One solution with short blades is to mount the jig as close to the handle as possible and pivot the handle on the knife upwards while sharpening and not follow the curve on the blade.

Sincerely,
Stig