On 2015-04-04, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
unk fired this volley in
:
...but it's not a one-off, this is an idea for a friend who might use
MANY of these bits so eliminating a few steps for a few cents extra
makes sense.
If you have a lathe, and some reasonable measuring tools, 'part
duplication' is a fast and easy process. About the only departure from
'normal' would be adding a compliant die adaptor to your tailstock to
handle a 1/4-20 die (point threading wouldn't suit for rapid
duplication).
[ ... ]
Then re-chuck the cutoffs, turn the minor diameter and thread them. The
'compliant' die holder is so you can force a start, then stop the die
with the spindle switch before it hits the shoulder. Then you just hand-
turn the last two or three threads, and reverse the spindle to get the
die back off the end.
Even better -- if you have a bed turret available for your
lathe -- is to use something like a Geometric die head. It cuts to the
point where your turret stop is for that station (another station does
the drilling, and another perhaps a bit of finish turning before
threading), and when the stop is hit, the threads already cut pull it a
bit deeper, until it releases a clutch which lets the four chasers pop
out radially to clear the workpiece so you can withdraw the die head
while the workpiece is still spinning. If you set it up right, you can
thread right up to a shoulder at fairly high spindle speeds.
But -- if the threads in the aluminum are going to be used for
frequent adjustments, you probably want to look into a rolling threader
instead. No chips, and the thread material is work hardened for better
life.
Quick, easy, cheap. (but I don't know how much you 'pay' yourself for
such mundane work).
If his friend is going to be making things in the thousands, it
would make sense to find a commercial part which would serve -- or find
someone with a screw machine lathe and automate the production. Run it
one day and have 10,000 of the parts you need. :-)
Enjoy,
DoN.
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