Bob & Patsy Keith, via e-mail:
Is there a standard to go by to know if my lathe chisels are
sharp enough? I might also ask...what is TOO sharp?
How sharp is sharp may not the only question here. Answering, "What
is the proper angle?" may also help with successful lathe turning.
I would add that not only angle, but technique has a lot to do with
the results when turning. A sharp scraping tool ground at a long
angle will gouge into the wood causing tearing and require MUCH
sanding as well as frustration.
Scraping tools (such as the Round Nose) should be ground at 80 to
85 degree bevel angle. They require no honing (the burr cuts too).
They must cut exactly on center of the rotating stock with the tool
held horizontal. This tool cuts by tearing the fibers across grain.
When done correctly, this leaves a smooth surface that requires
some sanding and is easy to learn.
and cutting tools require a low, long bevel angle (sometimes as
low as 15 degrees). They require honing the cutting edge to a fine,
razor-sharp edge. They are used above center, at an angle to the
rotating stock. This technique will sever the wood fibers at a shear-angle
rather than tear the fibers perpendicular to the grain, as in scraping.
technique of sharpening as well as turning takes many hours of practice
(and sometimes frustration) to learn but the results will leave
a much smoother surface that, in some cases requires no sanding
at all. Sharpening can be made much easier.
offers a couple of great sharpening systems for lathe chisels. The
first is our Sharpening
Guide Kit, that works on the MARK V with the Disc Sander. The
second is our brand-new Strip
Sander Chisel Sharpening Kit, it has been designed to work with
the Shopsmith Strip Sander.
best test for a razor sharp edge is how easily it cuts through the
end grain of a hard wood such as maple or oak...though I also use
sharpened chisels to shave a small patch on my arm as a quick test.
. . .