(03-10-2020, 03:48 PM)blgentry Wrote: You see, with the KR, the angle is not a wedge you are sitting on top of. Instead it's a SPACE between the table and the abrasive. So, when you set the blade body on the rest and it has (for example) a 4 degree included angle, you are getting CLOSER to the abrasive. With an angle wedge the body lifts further away from the abrasive! The tool rest is backwards from this. You get closer to the abrasive, therefore the edge angle is DECREASED by the body of the blade. Wow. I know, I know, it's just basic geometry but for me it was a wow moment.
Which means that if I set the KR to 15 degrees and I put my 4 degree (inclusive) blade body on it, I'm going to be grinding in a 13 degree edge angle. Or said the other way, if I want a 15 degree edge angle on my 4 degree blade body, I have to add the offset. 15 (edge) + 2 (offset) = 17. I need to set the KR to 17 degrees in order to get a 15 degree edge angle on this 4 degree blade body.
Mr. Brian, you are correct!
The angle of the adjustable guide of the Kallyrest has to be increased by ½ of the (included) taper angle of the blade.
Jan
P.S.: Mr. Grepper, the figures from my example are biased, probably because the grind of the blade was convex. Numerically biased but qualitatively OK.