On Wed, 01 Oct 2008 15:55:31 -0500, Wayne
wrote:
F. George McDuffee was thinking very hard :
On Mon, 29 Sep 2008 17:34:30 -0500, Wayne
wrote:
A friend at work has a wine press which needs some help. The internal
threads of a piece that moves up and down on an acme thread are
damaged.
I've been unsuccesful at getting him to bring it so I can measure it.
Through other methods it appears to be 1.25 x 3 TPI (or possibly
M32 x 8.5). I haven't been able to find any sources for any acme
nuts of that size. The lowest the my lathe will go is to 4 TPI.
It will also do 6 or 9 TPI.
Is there anyway to fudge a 3 TPI?
Wayne D.
==========
It depends on your lathe, and what change gears you have, can buy
or can make. Even with a quick change box you can generally
change some external gears between the spindle and box and get a
whole other range of threads.
Bear in mind that your thread dial may not work with the new
gears and you will have to leave the half nut engaged. Also note
that cutting 3 TPI with a 8 TPI lead screw requires the lead
screw revolve about 3 times [8/3s] faster than the spindle and
this can be a considerable load/strain on the gear train. Some
of the old old lathes had a set up to drive the lead screw to
reduce the strain for very course pitch threads. Acme threads
are tough anyhow so take it easy.
A good reference is http://lindsaybks.com/bks7/sscut/index.html @
$4.95
Let the group know how your make out and good luck.
Unka' George [George McDuffee]
-------------------------------------------
He that will not apply new remedies,
must expect new evils:
for Time is the greatest innovator: and
if Time, of course, alter things to the worse,
and wisdom and counsel shall not alter them to the better,
what shall be the end?
Francis Bacon (1561-1626), English philosopher, essayist, statesman.
Essays, "Of Innovations" (1597-1625).
Thanks for the input. Everything I do seems to take a long time.
I have started experimenting taking bigger cuts, but still am
conservative. I'd never make it in the real world of machining.
So if I tried an inside acme thread it'd probably be a day
or 2 project for me.
Wayne D.
==========
Although considered an obsolete accessory, a lathe spindle hand
crank is almost a necessity for this type of project.
see
http://mcduffee-associates.us/machin...ndle_crank.htm
Also be reminded that if this is indeed a metric screw both
metric Acme [29 degree included thread angles] and metric
trapezoidal threads [30 degree include thread angle] exist.
Good luck and let the group know what you find out and how you
make out.
Unka' George [George McDuffee]
-------------------------------------------
He that will not apply new remedies,
must expect new evils:
for Time is the greatest innovator: and
if Time, of course, alter things to the worse,
and wisdom and counsel shall not alter them to the better,
what shall be the end?
Francis Bacon (1561-1626), English philosopher, essayist, statesman.
Essays, "Of Innovations" (1597-1625).