ours will , and its a rinky little nardini we make some threaded parts
on a larger scale than what the o.p. is looking at and the threads have
to be timed 90 degrees from each other , i dont know why but thats what
the print calls for ,
I've never done it, but what I would try is this: Make the sleeve and
simply tap it. Run a 5/16-18 threaded rod into it with a locknut on it.
Chuck it in the lathe and engage the half nut with the threading indicator
zeroed. Line the lathe up on the threaded rod, turning the lathe over by
hand and adjusting the threaded rod as necessary (be aware of the lash in
the lathe...). When you have everything lined up, tighten the locknut. Now
the lathe will be lined up horizontally on the bottom of the thread. Move
the carriage (by turning the lathe over) to put the cutting tool over the
sleeve and move in the crossfeed until it touches. Note the readings on the
crossfeed and the compound (again, roll the lash out) and do a little math
to figure how to set them so that, after you've cut the thread, the point of
the tool is at the same place horizontally, but is now laterally at the
bottem of the thread.
I hope this isn't too confusing. Just be aware of the lash in the lathe and
you probably will need a good magnifier to get the tool lined up at the
bottom of the thread on the rod. If you need to be really fussy, don't
forget to allow for the slight movement (fit tolerance) the rod will make
when you tighten the locknut.
Can you single point threads? If so then this will work: Machine to
finished length and tap all the sleeves. Then put a piece of stock in
the lathe and single point a 5/16-18 thread on it the length of the
sleeves. This thread should fit the sleeves snugly. Finally, screw
each sleeve on it and single point your 18 TPI thread on the outside.
The parts will get stuck on the threaded mandrel because they will
tighten up on it during threading. This means you will need to come up
with a wrench to loosen them. If just a few parts a nut sawed in two
and clamped onto the threaded sleeve with vise grips will work without
damaging the threads. For nice threads use a full profile threading
insert. You can either buy or make a tool holder.
Thanks all, actually this was not for me but another fellow who works on
cues. He asked me how to do it and thought it would be easy to do and I told
him I thought it would be difficult. Looks like I'm right. He thought he
could just single point the inside and then the outside and they would stay
in sink. I told him that wouldn't work as you would have to change tooling
and that even if he ran the lathe in reverse for the inside threads and then
kept the same tooling for the outside they would still be out because of the
backlash in the lead screw between forward and reverse. I'll contact him
right now so that he can review these answers.
Thanks very much,
RHN Custom Billiard Cues
Building fine cues for real pool players at
Single-point both threads, with inside and outside
tooling adjusted so that they cut at the same point
(use left-handed boring bar for "normal" OD turning,
bars have same length so adjustment is easy). Both
threads can be cut the same direction, so the backlash
is not important.
Could be done with normal OD thread turning tool with
some effort to set the ID thread boring bar and the OD
tool cutting point difference to be a multiple of thread
pitch. Just put one tool to quick-change holder, measure,
and then put the other tool to another holder and adjust
the position vs the previous measurement so that the difference
is a multiple of pitch.
Yet another way would to be use tap or ID thread turning tool
to make the inside threads, then make a treaded holder for the
sleeve, so that the sleeve is fixed to the thread same way
every time. The holder needs to be fixed vs. spindle - could be
between centers with driver centre/dog or at a chuck. Now, just
adjust OD turning tool vs. the thread of the holder (before
putting the sleeve in place), and turn the OD threads to sleeves
one after another.
When you cant seem to create a small enuf thread ...
use a coupler nut , cut threads on outside that are
diff by 1 thread in 20 feet ! Did i exagerate ?
You now have a differencial "incher" .
Move one , one way and the other the other way , and the differencial
will move something by microns !
But of course you must fine lap the threads ..
I have a book of mechanisms ..... fun fun fun ....
Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here.
All logos and trade names are the property of their respective owners.