Knife Jig Attachment and Calculator Use

[John_B]

One of the takeaways from the recent knife sharpening videos produced by Tormek is attach the jig so that the front edge is parallel to a line drawn from the point to the heel. On a good many knives this results in a fairly straight alignment of knife and jig. Measuring the jig base to edge distance is straightforward for these knives. Knives with a more pronounced curve will be attached to the jig so that the jig adjuster face and the knife edge are at an angle. My assumption is that the measurement of jig face to knife edge should be made in the center of the knife. Most of the jigs I have seen would work well on the first case of knife types where everything is fairly parallel but a different method might be needed for more curved knives.

[cbwx34]

One of the takeaways from the recent knife sharpening videos produced by Tormek is attach the jig so that the front edge is parallel to a line drawn from the point to the heel. On a good many knives this results in a fairly straight alignment of knife and jig. Measuring the jig base to edge distance is straightforward for these knives. Knives with a more pronounced curve will be attached to the jig so that the jig adjuster face and the knife edge are at an angle. My assumption is that the measurement of jig face to knife edge should be made in the center of the knife. Most of the jigs I have seen would work well on the first case of knife types where everything is fairly parallel but a different method might be needed for more curved knives.

I'm not sure why Tormek adopted this method of setting the knife... it came from sharpeners like the KME... where the knife is clamped in place and the stone is on a pivot that moves up and down the edge.  (Even there, it's not really correct).  Personally I wouldn't use or recommend it.  There's no reason for it... at least not one I've found... especially using the stock setup. 

If you use a "pin pivot" collar, and want to clamp a knife where you pivot as you move along a curved edge... draw a line across the stone, and clamp the knife so it stays close to that line.  You'll see it as no relation to the method Tormek describes.

I would, after clamping the knife, just measure the Projection Distance like any other knife... just put the knife jig straight down the ruler or measuring device, and use the resulting measurement.  That way you'll have a consistent method (which I often say is just as, if not more important than accuracy).

[micha]

CBW, I second your proposals. Seeing that method of clamping had me thinking, too.

I think that recommendation was a little arbitrary, and if you actually start pivoting with the standard collar, the results will be quite unpredictable because of alternating pivotal points.

I also think it's more consistent (and more repeatable) if you clamp the knife straight and follow its curve by lifting.
And if we really need to pivot, one of the pin pivot collars will give way better results. 

Just my thoughts, I may be missing something...

[John_B]

Most of the knives I sharpen are fairly straight. The only one that I have that is curved is a skinning knife that rarely need sharpening. I have always mounted the knives in the jig as straight as possible and lifted the handle as I sharpened the curved portion. What I always try to do is to keep my contact point on the wheel constant as I lift. This seems to produce a consistent bevel for me.