That could propose a problem, especially using tool steel. A carbide insert
though will cut it. The only thing is you have to take a deeper cut sometimes
as something will give when the tool meets the work. In other words, dial it in
for a 0.001" cut and get a 0.0005" one. That takes some experience though, and
trial and error. I worked at a machine shop, running a 10 foot bed lathe, and
used to have to turn/bore hardened pump parts. I've actually seen a boring bar
at least 1-1/2" to 2" diameter deflect when taking a cut. You would mic the
bore and find you removed very little if none at all. We didn't have a toolpost
grinder handy so we had to do it this way. That's another thought on the
threads, is to use a thread grinder. That's expensive though as those wheels
are very expensive. One would need to send out the stem to a custom shop to do
this. They use these machines to grind the threads on taps. Case hardening
though, the part is softer so far under the surface so you h
ave to watch for that. About the best idea would be to have somebody like
Cleveland Twist Drill, or another tap manufacturer make a die for it. Then set
the die to be loose with the set screw (split die) so it will clean up the
boogered threads and not try to cut them any deeper. A carbide die would be way
better than one made of tool steel here.
Best,
Will
*********** REPLY SEPARATOR ***********
On 3/14/06 at 7:13 AM HAROLD B MANDEL wrote:
>Dear Will,
>
>>From what I remember of the Jennings lead screws they are
>case-hardened.
>
>This puts a dent in the one - to five thou cut, huh?
>
>Hal
>On Mon, 13 Mar 2006 19:24:30 -0500 "Will Matney" <craxd1@verizon.net>
>writes:
>> Al's correct. For any who want to try it, the way I used to chase
>> threads on a lathe was as follows. First, mount the shaft and bring
>> it into round with your dial indicator using a 4 jaw chuck. Next,
>> bring the carriage up close to the work, and engage the half nut
>> lever while watching the thread dial for the proper place for even
>> and odd number threads. Let the carriage run until the tool holder
>> is in front of the thread. Stop the lathe and mount the V-tool in
>> the tool holder. Push it into the thread until it bottoms out. Make
>> sure it is aligned straight into the thread. Note what number you
>> dropped the half-nut in on. Back the tool out of the thread and
>> watch how far out it takes to clear using a dial indicator behind
>> the cross-slide (for example 0.1"). Release the half-nut and back
>> the carriage back towards the tailstock out of the thread. Run the
>> tool in the amount you noted on the indicator before (0.10"
>> example). Start the lathe, and watch for the same number on the
>> thre
>> ad dial you recorded. Drop the half-nut in on this number and try
>> to clean it up first with the tool just tipping the bottom of the
>> thread. If this dont work try taking about a 0.0005" to 0.001"
>> deeper cut than what the bottom depth is. This being add that to the
>> 0.10" example you backed the tool out by. 0.005 to 0.001 inch will
>> make the fit of the thread looser but will clean it up. Remember,
>> what you take on one side reduces the OD by two times. Keep a set of
>> thread wires and a mic handy too. That's about all I can think of
>> but using a good cutting fluid sometimes helps.
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