jim rozen writes:

First off, what surface(s) are you hand-scraping, and to what
are they fitted?

The outer rim is what gets scraped, not in the usual machine-tool scraping manner (I think, not ever having done that) but
with a heavy wood plane blade or a cabinet scraper. The reason it gets scraped is to smooth it for the contact with the
strings. The strings rest on the wheel, which is rosined and acts like a bow. To keep the tone even, the wheel must have
very little runout: if there's variation in the diameter, the string pressure on the wheel varies, and the sound changes.
Instead of getting a nice smooth "ummmmmmmmmmmmmmmmmmmmmmmmmmmmm", it sounds like "MMMMMM-mmmmmm-MMMMMMM-mmmmmm".

I would suggest that you consider simply mounting the phenolic
blanks in OD jaws and and profile both sides, then mount on your
shaft or mandrel and take a skim cut across the OD to clean it
up.

The shaft you are using is pretty thin and flexible, that may
be where some of your chatter is coming from.

Initially when making the wheel I put the sawn blank on a faceplate to turn it down to the basic diameter, and to drill and
tap it (5/16"-18). There is less chatter in this situation, but of course the shafts have a little runout, and the tapped
hole is never exactly perfectly square to the blank - so between these two, there's always some runout in the wheel when it's
on the shaft. Consequently I make up matched sets of wheels and shafts: once a set has been assigned to an instrument, it's
not interchangeable with another set.

LE phenolic can be somewhat abrasive so if you are using HSS
tooling it will get beaten up pretty fast. Carbide if used
instead should be *un*coated as the coatings require a honed
edge and the phenolic really wants a sharp tool and fairly
large postive rake. My personal favorite for this is polycrystaline
diamond inserts from Valenite. I run the tpg221 sized ones
for composites and they last forever and give real sharp
edge.

My past experience with carbide, at least with metal, is that the poor old 9" SB lathe wasn't rigid enough for it.
Suggestions (besides a bigger lathe)? I'm using an Aloris QC toolpost.

You will also find that much of the aroma from turning phenolic
goes away when cutting with a very very sharp tool. I think
most of it has to do with burning at the cutting edge.

That would be nice. ;-)

A beefier mandrel as suggested would be a good way to go.
This is how we used to make sheaves, three operations - profile
first side, profile second side, and mount on mandrel and
turn OD.

The sides are less important - just the OD (which is not square, but is cut at several degrees angle.)

Thank you,

Alden
--
Alden F.M. Hackmann
Web: http://www.hurdygurdy.com/hg/hghome.html
"Beati illi qui in circulum circumeunt, fient enim magnae rotae."