On Jan 1, 12:55*am, Don Foreman wrote:
I will agree the only way to do it properly (even on a cnc lathe) is
with gauges (go and no-go). This is an odball thread but using the
machinery handbook you can figure out the proper dimensions. On page
1733 of the .pdf version of the 17th edition it has a diagram of the
unc/unf thread series. You can use the values there to calculate your
thread depth and Minor diameter. If you want to make a thread gauge
so that you know the threads are %100 correct on pg. 1922 of the same
pdf gives the standards for computing the dimensions for a thread
gauge both go and no-go sizes.
In all reality, this is not necessary if you are just making a collet
closer. You can just figure out the root dimension of the 1.238-20
thread (1.19469 check my math.... ) and then cut your ID about .010-.
015 larger and cut your threads until the collet spins cleanly into
the thread.
-Brian
On Thu, 31 Dec 2009 20:15:48 -0500, Wes wrote:
I'm making a 5c collet closer, the collet thread afaikt from the internet is 1.238-20.
I'll freely admit, I generally just look up threads in machinery's handbook and cut the
thread.
That one isn't in there.
I'm thinking that boring my chunk of 1 3/8" 4130 tubing to *1.238 - 1/20 is a possible
solution before threading, much like calculating a tap drill. *Then using my selection of
collets to check for fit is a plan that may work.
I'd really like to know how to calculate this as in I'll build a spreadsheet for future
oddball threads.
Thanks,
Wes
DoN Nichols wrote a little program that John Beidl made usable under
Windows. I've been using that for years.http://www.metalworking.com/dropbox/...s/Threadsw.txt
The one I use is v5.0.0.0, 2 Mar 99. It's worked on every Windows
machine I've owned, currently running Win XP Pro. *
A formula that seems to work for internal threads is:
ID = OD - .975/TPI
I made a spreadsheet with these values and printed a chart that is
taped to my lathe. *
It's a guide, not gospel. *I've made parts to fit a mating part 1500
miles away (and they did) but with internal threads it's really best
to have a try gage at the lathe if at all possible. Perhaps not so
true with ultra-rigid CNC machinery, I don't know anything about that.- Hide quoted text -
- Show quoted text -