I don't know if it makes any real difference, especially on the
outside of the bowl which is convex, although most use an 8 inch
wheel, and some a 6 inch wheel, and some others use a metal belt
sander which will leave a flat surface. On the inside of the bowl,
which is concave, you will be riding more on the back point of the
bevel. I do relieve the edge of the bevel for inside the bowl turning
so the sharp edge of the bevel isn't rubbing on and bruising the wood.
I have never tried a double bevel, but do have gouges with a couple of
different bevel angles from more pointy for the outside, to very blunt
for the bottom of the bowl.
robo hippy

On Mar 18, 3:36*pm, Fred Holder wrote:
On Mar 18, 2:20 pm, John wrote:



A thought came to mind today whilst sharpening some gouges, what is the
optimum grind.

Let me explain

If I grind a tool on a 3 inch wheel I get a bevel with a radius of 1.5
inches,
but
If I grind a tool on a 12inch wheel I get a bevel with radius of 6
inches.

I would guess that the ideal radius of the grind would be larger than
the radius of the piece of work? My understanding is that if the radius
of the bevel were less then you would ride the back of the bevel until
the front touches, nothing in between, with an increased chance of dig
in on contact. If it is larger radius you can pivot on any point of the
bevel till the front touches, better control *and less chance of dig in
on contact..

So assuming I have this correct, what is the best bevel radius to use
when you start getting to a really large diameter turning say 24inch
dia? Would no bevel be the best option ?

--
John

Hello John,

What many people do to eliminate or reduce this problem is the use two
bevels. One is a short or narrow bevel at the cutting edge and then a
secondary bevel which grinds away a part of the heal of the bevel.
With this method, there is a very short bevel riding on the wood and
the problems you describe disappear. The actual cutting bevel is
generally about 1/16 inch to 1/8 inch wide. The rest of the normal
bevel is ground away at a different angle to get it out of the way
when turning.

My recommendation would be to give it a try and see how you like it.
I've used tools with no more that a 1/16 inch wide bevel with
excellent success. Several well known turners do this.

Fred Holder
http://www.morewoodturning.net