Positioning the SVM-45

[Tom Maynard]

On page 116 of the User Manual there is a classic "Goldilocks" illustration of the positioning of a knife in the jig: (a) too close to the handle, (b) too close to the tip, and (c) "Just Right."

I've been wondering about this.

If there is a "just right" mounting point for each knife in the jig, there must be a way of determining where that point is.  I'd like to eliminate the eyeball guesswork (and the chance of a later "Ooops -- wrong spot)", and be able to position the knife in the jig algorithmically.

How is the optimum mounting determined?  The manual illustrations oversimplify the task by showing the "just right" mount in the middle of the blade.  I know from personal experience that this isn't always correct (not all blades are the same shape!).

Any input is appreciated.

Tom.

[Jeff Farris]

This opens up a huge can of worms, but maybe we can work through it.

First, if you watch the TORMEK video, the SharpToolsUSA DVD, and read the manual on page 119, you will find that none of those agree with the illustrations on page 119.  I think it is a matter of old artwork being recycled even after improved methods have been developed.  In the video instructions, you will see that the movement to keep the blade on the stone is axial to the shaft of the knife jig. In other words, if the shaft of the jig were the center of a clock, the handle of the knife is moved like the hands to follow the contour of the knife on the grindstone. The flat area of the jig head (the black plastic part) should remain in contact with the Universal Tool Support at all times.  

Once you start using this method, instead of riding the radius on the edge of the jig head, jig positioning on the knife is much less critical.  I usually position the jig so that it is parallel with the straightest part of the blade (which is generally not parallel with the back of the blade), and approximately centered on the length of the blade.

[Tom Maynard]

> This opens up a huge can of worms, but maybe we can work through it.
Nothing better than canned worms for a light snack!  

> the movement to keep the blade on the stone is axial to the shaft of the knife jig
Golly, you're speaking my language!  (Few people do these days.)  So, if I understand you correctly, lifting the handle of the knife cancels out the critical positioning of the jig?  In fact, you say exactly that so it must be so.

> parallel with the straightest part...approximately centered on the length
Well, I think I can manage that.  And at that point working the tip of the knife becomes essentially identical to the motion used in manual sharpening on a bench stone with an edge guide.

Thanks.