Re: [CAD_CAM_EDM_DRO] Re: Cost estimate for machining of acme screws

In a message dated 11/17/2002 1:10:55 AM Central Standard Time,
elson@... writes:

> On my Atlas lathe, it would probably take a half hour for the first one, and
> maybe 15 minutes for each after that. With a 'real' lathe, it might get
> closer to 5 minutes each. It would take a bit longer if you wanted the
> ends ground instead of a turned finish.
>

Assuming you would just "chuck up" on the O.D. of the screw as simply as you
would with any length of CR rod, I would totally agree with your numbers,
here. But if you fiddle with some brass sleeve (I have made those for my
own similar applications in the past) to slip over the O.D. of the screw to
protect it from the chuck-jaw-teeth (even a "smooth" collet has three grooves
which COULD make "nicks" in an otherwise-very-smooth screw-O.D.!) it can take
more! None of us (or few, anyway) have mentioned "tolerance" for this
operation. Assuming you would want to press-on a ball-bearing, we would want
-0 to +0.0005", so the screw-end will press-into the ball-bearing without
"hydraulic force" required. But more than just an "interference fit"! It's
reaching, measuring, and ENSURING that rather precision O.D. that is the
time-consumer here!

Now, if you have a dozen or more such ends to do, with professional
experience in setup, and a very fine Hardinge, etc., lathe, you could do
these in only a couple minutes, each, perhaps even including "last-pass
measurement", but I still assert that "first one" would, as you say, take at
least a half-hour!l

But, wow! This is SURELY far-off-topic, particularly, by now! And in the
past when we've gotten off on "machine-shop tangents" like this, Bill has
jumped in our [deleted] and spanked us heartily! Wonder why THIS topic has
been tolerated for so long????

Jan Rowland



[Non-text portions of this message have been removed]