In article ,
Alden Hackmann wrote:
jim rozen writes:

Hmmm. I would stay away from a tapped hole to mount it to the
shaft, for the reason you say, this does not provide good
locational accuracy for the finished assembly. A better
design would be a straight bore in the phenolic, and a
round section on the shaft. The shaft could have a shoulder
at one side and threads on the other, a nut could compress
the phenolic up against the shoulder.

This doesn't work with the system we're using, for esthetic reasons.
;-( However...

The nut doesn't have to *look* like a nut. It can be a cone,
with pin holes or grooves (which could be disguised as decoration)
allowing a special wrench to tighten it firmly.

Add that to an anti-rotation pin (as I just suggested in another
branch of this thread), and you assure that it goes back in the same
position.

Tapped holes do *not* work well if you are trying to minimize
radial runout. Just taking the part off the shaft, and putting
it back on, will give you a few thousanths of error right there.

How about a wheel that is tapped (half) and reamed (half)? Would the
phenolic threads hold up?

How thick is the wheel at the hub? What pitch are the threads?
I think that you are using a wheel of about 1/2" thickness, which is not
really enough if half of its length is taken up by threads. And the
rather coarse threads which would seem to make sense in phenolic would
result in not enough of them to really trust.

Otherwise, this is similar to how a lathe's spindle centers its
chuck, with a register shoulder and threads for the force.

Do you ever encounter a player who likes to turn the wheel
backwards most of the time? Do you have problems with it coming off
under those circumstances?

I would think so. Would the half that's
bored straight be enough to stabilize it? That's the way we used to do
it, with a nylon insert in a wood wheel, until we had several incidents
of the nylon threads being stripped.

I think that this answers your question. :-) It just isn't long
enough to devote half of the thickness to threads and half to a reamed
hole for centering.

Does the shaft stick out much beyond the hole? If not, a
cone-shaped nut could look rather nice, and be a lot stronger than the
phenolic, let alone than the nylon.

BTW Have you looked into using Delrin (acetal) for your wheel? It
is available in both Balck and natural (a sort of light cream
colored white. and is a lot more durable than nylon.

Good luck,
DoN.


P.S. Can you trim your line length a bit? Standard length should
be no longer than 72 characters, to allow some levels of quoting
before they start to get folded. I've been having to re-format
your lines so the whole of the text is visible in my editor,
instead of part of it hiding beyond the right margin. Since
some are worse than others, I suspect that you are using a
proportional pitch font for posting (which means that ASCII
graphics will appear distorted -- including my earlier attempt
to show the shape of the special Aloris tool holder which would
be more rigid than what you are using. If it was
unintelligible, go back to look at it with a fixed pitch font
selected, such as Courier (always a safe choice. :-)
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