In article ,
Alden Hackmann wrote:
(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.

O.K. So it should be on-axis, then.

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

[ ... ]

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.

O.K. I can see that. But a gentle press fit, not a firm one
might be do-able, with the pin dropped into a hole through about 2/3 of
the shaft's diameter at the last moment before entering the wheel. (I
presume that it would otherwise have problems feeding through the
bearing at the crank end.

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.

Thus a need to be able to assure the orientation of the wheel
relative to the shaft on re-assembly in the instrument.

[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.

That would probably make it a lot better for your purposes.

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.

O.K. Let's see what I can find (but the first clue is that the
wimpy ones come in sets of five, sometimes boxed, sometimes in a wooden
stand with holes for the five cutters, two spare screws for attaching
the inserts, and one or two hex keys (Allen wrenches) for the screws.

Names like Valenite and Carbaloy are found on the good ones,
plus some from Israel (Iscar). Let's start on page 617, upper left-hand
corner, for the PCD tipped inserts. (These would last a lot longer and
do a cleaner cut on your composite wheels. (From those, you can select
holders to fit the inserts available. (*Don't* use these on iron or
steel, however, it will convert the diamond to extra carbon in the steel
alloy, which doesn't help you at all.

If you use carbide, don't use the TiN coated ones (or the other
coatings), as it results in a slight rounding (dulling) of the edge.
Good in working steel, but bad for composites.

You'll have to stick to 1/2" square shanks, thanks to your
toolholder. Look for ones with carbide anvils as separate replaceable
items. it gives better support to the inserts. Valenite holders start
on page 622. Some styles are not available in the 1/2" size, which is
another thing to control your choices. (Find a combination of inserts
and holders which will work with your lathe and your materials.

Valenite is only one good brand, and happens to be first in the
catalog. (Reverse alphabetical order by any chance?)

Page 633 includes a diagram of how at least one style of good
holder goes together.

The cheap sets are shown on page 553, and I've found them to be
inadequate even for a 5" Emco-Maier Compact-5/CNC. Once I found a good
supply of the diamond inserts which fit the tools which came with it, I
was quite happy, and have totally retired the cheap sets.

I hope this helps. I'm putting the catalog back on the shelf
while I've still got some circulation to my legs. :-)

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.

O.K. But angled to match the angle of the strings?

Thank you for your comments,

You're welcome. I hope that they help.

Good Luck,
DoN.

P.S. My wife recognizes your name from some of her newsgroups (and/or
mailing lists).
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