Author Topic: Knife Jigs Solution  (Read 23530 times)

Offline wootz

  • Hero Member
  • *****
  • Posts: 509
    • View Profile
    • knifeGrinders.com.au
Knife Jigs Solution
« on: March 16, 2016, 08:05:43 pm »
This is to solve annoying bevel asymmetry.
Jig #1 - up to 3mm thick knives.
Jig #2 - for 3-4mm thick knives.
Jig #3 - for 4-5mm thick knives.
Jig #4 - for 5-7mm thick knives.

For centering knives in the jig I use blades from a Feeler Gauge with 1cm wide blades as shims, as explained below.



Tormek Knife Jig SVM-45 has 1.1mm spacing from the centreline of the handle to the bottom of the knife clamp (the static part of the clamp) - thanking Jan for the exact figure.
Ideal for 2.2mm knives, but well acceptable for 2-3mm thick as well.
Knives thinner than 2.2mm will get the top bevel higher, whereas knives thicker than 2.2mm will get the base bevel higher; the further from the ideal 2.2mm thickness, the more noticeable is the bevels asymmetry.

For knives 2mm and thinner I use shims.
Measure thickness of the knife at the clamping spot, and divide by 2 - you get spacing to the centreline of the knife.
Difference between 1.1mm and halved blade thickness is filled with a shim.
Shim is placed on the bottom jaw (the static part of the clamp).

Example
Knife thickness 1.7mm, divided by 2 = 0.85mm.
1.1mm - 0.85mm = 0.25mm shim.

Obviously, for knives thicker than 2.2mm you cannot put shims in the standard SVM-45 - for them I use second jig where I ground away 0.5mm from the static clamp.
Spacing from the centreline of the handle to the bottom of this jig is 1.1mm + 0.5mm = 1.6mm
Ideal for 3.2mm knives, but well acceptable for 3-4mm thick as well.

Third jig with 1mm ground off the static clamp.
Spacing from the centreline of the handle to the bottom of this jig is 1.1mm + 1mm = 2.1mm
Ideal for 4.2mm knives, but well acceptable for 4-5mm thick as well.

Example
Knife thickness 3.9mm, divided by 2 = 1.95mm.
2.1mm - 1.95mm = 0.15mm shim.

Fourth jig is adapted Triton Long Knife Jig with 3mm ground off the static clamp. Triton jig has no offset.
Spacing from the centerline of the handle to the bottom of this jig is 3mm.
Ideal for knives 6mm thick at the spine, but can be used for 5-7mm thick as well.

Shim is always placed on the bottom/stationary jaw.



« Last Edit: August 08, 2018, 12:12:04 am by wootz »

Offline Ken S

  • Moderator
  • Hero Member
  • *****
  • Posts: 6674
    • View Profile
Re: Knife Jigs Solution
« Reply #1 on: March 16, 2016, 10:14:38 pm »
Clever, Wootz. This makes a good jig more versatile.

Ken

Offline Jan

  • Hero Member
  • *****
  • Posts: 1341
  • Iron sharpens iron, and one man sharpens another
    • View Profile
Re: Knife Jigs Solution
« Reply #2 on: March 17, 2016, 03:47:43 pm »
Another great job, Wootz, congrats!  :)

You have brought the modification of the knife jig to perfection. It is really a professional set of knife jigs for all possible knife blade thicknesses.

Jan

Offline Ken S

  • Moderator
  • Hero Member
  • *****
  • Posts: 6674
    • View Profile
Re: Knife Jigs Solution
« Reply #3 on: March 17, 2016, 04:08:52 pm »
Well stated, Jan.

Ken

Offline SharpenADullWitt

  • Hero Member
  • *****
  • Posts: 667
  • I'm a sharp craftsman!
    • View Profile
Re: Knife Jigs Solution
« Reply #4 on: March 17, 2016, 06:36:19 pm »
How did you grind them so precisely?
Do you have some other sort of marking on them, so you don't accidently grab the wrong jig (since you have so many)?
Favorite line, from a post here:
8)

Yeah you know Tormek have reached sharpening nirvana when you get a prosthetic hand as part of the standard package :/)

Offline wootz

  • Hero Member
  • *****
  • Posts: 509
    • View Profile
    • knifeGrinders.com.au
Re: Knife Jigs Solution
« Reply #5 on: March 17, 2016, 06:49:59 pm »
I had them ground for me at a machinery shop.

Offline Ken S

  • Moderator
  • Hero Member
  • *****
  • Posts: 6674
    • View Profile
Re: Knife Jigs Solution
« Reply #6 on: March 17, 2016, 09:42:22 pm »
We should make more use of good machinists. I had a machinist modify my Omnijig (dovetail routing jig). That increased its versatility manyfold.

Good show, Wootz!

Ken

Offline wootz

  • Hero Member
  • *****
  • Posts: 509
    • View Profile
    • knifeGrinders.com.au
Re: Knife Jigs Solution
« Reply #7 on: March 17, 2016, 10:17:46 pm »
BTW the machinist told me the Triton jig material and accuracy is "utter crap" compared to Tormek's.
I resorted to Triton's only because it is thicker, allowing to grind off 3mm.
« Last Edit: March 17, 2016, 10:27:34 pm by wootz »

Offline Ken S

  • Moderator
  • Hero Member
  • *****
  • Posts: 6674
    • View Profile
Re: Knife Jigs Solution
« Reply #8 on: March 18, 2016, 12:57:28 am »
Wootz, if your machinist is impressed with the metal of the knife jigs, he will be blown away with the new zink jigs. It's just my opinion, but I believe most of the jigs will utilize zink in the next very few years.

Ken
« Last Edit: March 18, 2016, 01:01:13 am by Ken S »

Offline wootz

  • Hero Member
  • *****
  • Posts: 509
    • View Profile
    • knifeGrinders.com.au
Re: Knife Jigs Solution
« Reply #9 on: May 29, 2016, 12:44:20 am »
Knives with flat-sided wedge profile require more adjustment.
I noticed that sharpening flat-sided wedge knives I don't get equal bevel on sides even if the knife is 2.5mm thick in the original SVM-45 jig: theoretically I should be getting even bevel on each side, but it wasn't unusual to get 0.2mm difference in the bevel height between sides. You could see the asymmetry and it was damn irritating.
Then I realised that because sides of these knives aren't parallel at the back, the jig clamps the blade only at the very spine, and the blade plays even if clamped tightly and during sharpening moves from the centred position (rolls to one side).

Shims pushed from the edge between the blade and jig top and bottom jaws help to center the blade relative to jaws.
In the pictured example I used 0.004 inch (0.1mm) shim on each side, with perfect result.



« Last Edit: May 31, 2016, 01:10:25 am by wootz »

Offline angpanday

  • Newbie
  • *
  • Posts: 14
  • I'm a sharp craftsman!
    • View Profile
Re: Knife Jigs Solution
« Reply #10 on: October 10, 2016, 11:41:49 am »
Third jig with 1mm ground off the static clamp.
Spacing from the centreline of the handle to the bottom of this jig is 1.25mm + 1mm = 2.25mm
Ideal for 4.5mm knives, but well acceptable for 4-5mm thick as well.

Taking off a 1mm from the static clamp. Does it mean .5mm to be machined off on per side?

Offline Jan

  • Hero Member
  • *****
  • Posts: 1341
  • Iron sharpens iron, and one man sharpens another
    • View Profile
Re: Knife Jigs Solution
« Reply #11 on: October 10, 2016, 01:16:22 pm »
No, you always take off the metal only from the inner side of the static clamp. In this case you ground off 1 mm from the static clamp while the adjustable clamp remains unchanged. 

The small screw of the knife jig enables to adjust it to fit the spine thickness of the knife. No material is removed from the adjustable clamp. ;)

Jan
« Last Edit: October 10, 2016, 01:30:56 pm by Jan »

Offline Ken S

  • Moderator
  • Hero Member
  • *****
  • Posts: 6674
    • View Profile
Re: Knife Jigs Solution
« Reply #12 on: October 10, 2016, 04:45:30 pm »
I would have some unsupported reservations about deepening the groove in the ststionary jaw. My concern would be structural integrity, however, these reservations may well be unfounded. Realistically, the Tormek operates at 90 or 100 rpm. I don't think there is a safety issue, even in the unlikely event that the jaw should fail. Worst case scenario, a new jaw or jig is not expensive. I would give it a go.

I would size the depth of the groove to match your piece of steel exactly. Measure the thickness of your steel and halve that thickness.

Do keep us posted.

Ken

Offline wootz

  • Hero Member
  • *****
  • Posts: 509
    • View Profile
    • knifeGrinders.com.au
Re: Knife Jigs Solution
« Reply #13 on: October 14, 2016, 11:41:49 am »
The pictures show that grinding the stationary/bottom jaw won't weaken it thanks to the wedge profile.





Offline Jan

  • Hero Member
  • *****
  • Posts: 1341
  • Iron sharpens iron, and one man sharpens another
    • View Profile
Re: Knife Jigs Solution
« Reply #14 on: October 14, 2016, 01:03:30 pm »
Wootz, thank you for posting the detailed pictures of your modified knife jig. I guess from the shown static clamp 0.5 mm was ground off.

Regards
Jan