Thursday, February 06, 2014

Some Thoughts on Sharpening

I've been in the "Sharp Enough" school for awhile. While irons so sharp they make arm hair commit hari-kari (sorry I can't help myself sometimes) just by getting close are impressive the truth is at the first touch of wood the edge will fracture. At least for me I want an edge sharp enough to do the job well but at the same time resists early fracture.

With that preference I will usually sharpen chisels by hand, putting a slight convex curve to the bevel. It's fast, sharp enough, and gives a fracture resistant edge, I think stronger than either a micro bevel or flat bevel. With plane irons I've usually sharpened with either the Tormek or a honing jig like the Eclipse because I've felt jigs and/or the Tormek will produce a sharper iron and because plane irons usually do not endure the abuse chisels do. The extra time to use either the Tormek or a jig was a good trade off for plane irons. That may change.

I'm off today but have to work the next three days and there really isn't time to get involved in a big project so I thought I would run a very subjective test of my thoughts on sharpening plane irons. I have a #3, a #4, and a #5 Woodriver planes all with Hock O1 irons and chip breakers. I hand sharpened the #5, used the Tormek (with the 3000 grit Japanese water stone to finish) on the #3, and the Eclipse, using the same diamond stones I used to hand sharpen, on the #4. The hand sharpened iron and the jig sharpened iron were stropped on a horse's butt strop charged with Herb's Yellow Stone.

After re-installing the irons I edge planed some Sapele, Red Oak, Sycamore, and Cherry and face planed the Sapele. All very subjective but at first the Tormek sharpened #3 felt a very slight bit sharper while edge planing the Sapele but with the other woods I really could not feel any difference. The real difference came when face planing the Sapele. The Tormek iron and the Eclipse iron both had tear out, the hand sharpened iron was smooth as a baby's butt.

When I looked at the irons with a 20X lupe after the planing there was some slight fracturing of both the Tormek iron and the Eclipse iron. The hand sharpened iron looked just like it did when I first finished sharpening it.

I expect I will continue to use the Tormek on my 51 shooting plane iron and some of the smaller irons and plow irons that are hard to hold but for the rest I'll do 'em by hand. It's faster and just as good. YMMV.

Now some tool porn:

From left to right: Hand, Tormek, Eclipse

Not that you can tell anything but all post about planes must have a photo of the plane with shavings:

The hand sharpened iron:

The Tormek iron:

The Eclipse iron:

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