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True-ing SVM-45 knife jig

Started by summit sharpening, June 11, 2008, 05:26:20 AM

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summit sharpening

After experiencing minor differences in bevels from side to side while
sharpening knives, I tried researching the matter on the various forums
with little success. One poster mentioned that the knife jig may need to
be trued, but did not mention how. I stumbled across a reference
verifying the asymmetry of the knife jig:

'There is another problem with the Tormek knife holder. When alternate
sides of the blade are ground the knob seen in Fig. A4 will be
positioned either up or down. The die casting that composes the body of
the holder is apparently a bit unsymmetrical, so that the ? angle
formed in these two positions is a bit different. Experiments show that
the angle ground on the side when the knob is up, comes out larger than
with the knob is down. The difference was measured by the laser
goiniometer to be around 3.2 degrees, which means there is an asymmetry
of plus or minus 1.6 degrees when the holder is flipped. The ground
side of the blade oriented away from the knob has the larger angle by an
amount of around 3.2 degrees.'

-Experiments on Knife Sharpening (Pages 49 & 50)
(John D. Verhoeven Emeritus Professor Department of Materials Science
and Engineering Iowa State University)
http://www.cutleryscience.com/articles/index.html

Besides adjusting the micro-adjust or the knife jig's adjuster for each
side of the blade, does anyone have any other suggestions or solutions
(ie. metal spacer in jig)?

Most of the kitchen blades I sharpen don't warrant this attention to
detail, but a few of the more expensive Japanese blades do.

Does anyone know if there is also a significant (3+degrees) asymmetry in
the long knife jig?

Jeff Farris

I have not experienced the repeated asymmetry mentioned in Verhoeven's article.  Any asymmetry I have seen has been easily corrected by loosening the clamp slightly, rolling the knife slightly, and reclamping.  It is not necessary to "bury" the blade in the jig.  In fact, you will have the best results overall with the jig if you will just barely capture the back of the blade in the blade clamp.

By the way, Verhoeven did not contact us in any way when he wrote that article.  It is full of instances where he uses the Tormek in a manner contrary to its design and our recommended procedures.  I absolutely promise you that I can get far better results from the Tormek than he did, simply by reading the book that comes with the machine and following the procedures explained there.
Jeff Farris

summit sharpening

I do admit that I have been burying the blade in the jig.

By 'rolling' do you mean moving the tip up and down, or the blade left and right in relation to the knife?  

Jeff Farris

I mean centering the blade, relative to jaws so that the cutting edge
is visually centered between the top and bottom jaw.

Jeff Farris