How to Grind a Blade to Be Sharp Again

Here the perfect applied instance, the Spyderco Yojimbo ii. Its edge length is 75mm, and with this pocketknife model you lot are forced to start flush on the grinding wheel considering the obstructing knife's ricasso/eternalize would be in the style otherwise. Permit's assume that the border is 100.0% perfectly hateful-straight (because peradventure information technology was factory-ground on a 150mm wide large grinding wheel lol). And allow's assume that your grinding bicycle width is 45mm, i.east. narrower/shorter than the border length. Then i am challenge that repeated grinding sessions on this cycle will seriously concave the edge, no thing what you endeavour! In fact, even later the very get-go wheel grinding session ane could see the concaving effect through a 100.0% mean-flat reference surface, with lite shining through the concavity. I am not claiming that cycle grinding sessions will not sharpen the entire edge length; they will. All i am claiming is that bicycle grinding the Yojimbo edge on a 45mm narrow wheel volition instantly ruin the 100.0% perfect straightness of the edge. Solution? If you desire to keep the ex-fac perfect straightness, then either grind on a 80mm+ wide cycle or grind the blade on a "wide" 100.0% mean flat benchstone in such a way that each point of the edge gets

equal grinding time

, i.e. simultaneous grinding contact.

My thoughts on this topic in detail:

I was wondering about the exact maths when you starting time the wheel-grinding "flush", i.e. the heel is

resting on

the wheel with the heel being flush with one edge of the wheel, before you kickoff drawing the entire straight bract length along the wheel thickness w1. knifegrinders video shows that grinding on a bicycle could lead to a concaving of the (straight) bract section. i concord.

in lodge to avert the concaving event, in the video wootzblade suggests that we "spend more than time grinding the heel". i doht fully agree. permit's consider the extreme case similar the Yojimbo, i.e. a knife blade-handle-geometry which forces the user to starting time the grinding "flush", and the bract shape has a long straight blade section ending in the heel. then from the very outset the bike width is fully "covered with blade steel" and you leave that blade heel section lying on the grinding wheel. then as presently equally you lot commencement cartoon the bract in the proper management, the heel betoken (at 10 = x0) loses contact with the wheel whereas the "opposite" wheeling point (at 10 = x0+w1) withal gets grinding time T. And the slower you draw the blade, the much more than extra dwell time that is. in fact, that point gets the maximum of grinding time of the unabridged bract length. That point, or the section between the heel point and that point, volition eventually develop a recurve. To be crystal articulate, after a bike grinding session, the straight blade section will not be 100.0% straight anymore; this tin be easily confirmed by a subsequent honing test on a mean-apartment ceramic rock. Never listen the grinding wheel, this miracle is every bit true for grinding a direct blade heel section on a guided sharpening system (Ruixin, EdgePro, Lansky, KME, etc) or even on the 204MF: whenever the "grinding width" is so much narrower than the blade length, so it becomes incommunicable to maintain the mean straightness of the (direct) heel department.

Here are the maths and the computational confirmation that my formula is right:

I don't wait everyone to empathise the contents of the above two pics. The conclusion of the graphs/maths is: whatever you try to vary (making t0 shorter or longer or zero, increasing or decreasing v1), there is absolutely no way of grinding each indicate ten for an identical amount of time T(x).

Actually there is. Merely take a knife where you're not forced to get-go "flush", like a Santoku knife or a typical Japanese chef knife. Or cheque the last moving-picture show of my Berndes modding post; earlier the modernistic the Berndes geometry would take forced me start wheel-grinding flush, afterward the mod i could draw the blade across the bicycle width in such a way that each point x gets an identical amount of grinding time T(ten), and then its direct blade department would remain mean-straight even after repeated wheel grinding sessions.

maybe the accept abode message be: trying to distribute grinding fourth dimension equally over the entire edge length, i.e.

T(10) = const., for all x ​

is h*ll of a challenge! at least in theory.

Practice y'all take similar wheel-grinding experiences or other applied solutions for this "maths problem"?

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Source: https://www.bladeforums.com/threads/wheel-grind-a-straight-edge-without-overgrinding.1733595/

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