(DoN. Nichols) writes:

*Tapped* hole? You mean that the wheel threads onto the shaft?
How do you tap it? In the lathe, just after drilling, while still on
the faceplate? If you go to a drill press, you're introducing an
additional place where error can come in.

The wheel is drilled and tapped on the lathe.

I would instead of tapping it, drill it slightly undersized, and
ream to size in the lathe (or bore before reaming, to make sure that
things are on-center), and make that size a light press fit on the
shaft. Then I would use a tiny end mill, or a reciprocating saw, to
make a short radial slot from the center hole, and drill the shaft for a
pin which would be pressed in and prevent the wheel from ever rotating on
the shaft. I would have a thread on the shaft just *after* the wheel,
and a screw-on nut (perhaps with pin spanner holes) to secure the wheel
to the shaft. The shaft *should* have a shoulder to assure that the
wheel is square to the shaft, and to resist the thrust of the nut.

There is a shoulder, 1/2" diameter.

The press fit/pin/nut are a cool idea, but the wheel needs to fit through a hole that has minimal clearance (1/32" - 1/16")
around the wheel. I don't think the body would stand up well to the shaft being pressed in.

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.

Is the wheel permanently mounted to the shaft from the time it
is machined to final installation? If it comes off for intermediate
operations, and there is no pin or other feature to assure alignment
between the shaft and the wheel, each removal and replacement can
introduce more error producing runout.

The shoulder does this, I assume. The wheel is removed from the shaft after machining.

[much useful advice deleted]

4) Minimize overhang in the compound. Ideally, the toolpost should
be centered over the pivot/mount of the compound to the
cross-slide.

Ah, there's the rub - as it is, I've had to slide the toolpost back so ~1/2" is hanging out. I probably need to make the cool
flat cross-slide from Metal Lathe Accessories.

5) Don't use the inexpensive sets of five insert holders (parallel
left, angled left, neutral, angled right and parallel right), as
they tend to be rather wimpy, and to use thinner inserts,
without a proper Carbide anvil supporting them, so they break
much more easily, and otherwise lead to chatter.

Um - a little lost here. Could you point me to some MSC Big Book pages showing the wimpy stuff and some showing the good
stuff? I'm afraid that I wouldn't know a good insert holder if it fell on me... but in any case, I guess I know which inserts
I'm looking for, so I can let that choice help me to find good holders.

Isn't it crowned? That was how the ones which I made were
produced. (Back before I had such nice tooling and machines to work
with. :-)

The surface is flat, with a small radius at the edge to keep the string from being cut by a sharp edge. I've tried
instruments with crowned wheels - not a good sound. The surface is much better flat, like the hairs of a bow.

Thank you for your comments,

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