Hey Wes,,

If threading fully to a shoulder is absolutely necessary, then
sometimes it is possible to add the shoulder later by some means.
Depending on the "meat" forming the shoulder, it is possible to do a
trepanning cut that allows the thread to actually go BEYOND the
shoulder face.
Another thought is to undercut the "nut" part so that the face of the
nut contacts the shoulder, but there is a half a turn or so turned off
the nut, and the shaft thread can stop a half turn "short" of the
shoulder.

Good luck. Take care.

Brian Lawson,
Bothwell, Ontario.

ps....I realize the drawing was made only for your own purposes, but
for the rest of us to view it is nice if all the "text" part is set in
the same direction, and it is also standard practice to indicate the
threaded part(s) with an arrow and text describing it, rather than
just with dimensions
eg. 2-1/2 - 14 TPI -----------

XXXXXXXXXXXXXXXXXXXXXXXXXX



On Fri, 31 Aug 2007 15:54:29 -0400, Wes wrote:

Well, it is once again time for me to use an engine lathe to single point
thread. It seems to be something I do every couple years so I've never
realy mastered it.

I'm restoring a Clausing 6903 lathe that uses a varidrive.

The driven sheave has a crack in it.
http://wess.freeshell.org/clausing/6...it_a_crack.JPG

My bud tried to gas weld it with cast iron rod but it wouldn't close.

http://wess.freeshell.org/clausing/6903_gas_welding.JPG

Not much of a picture, cell phone camera though a welding helmet.

So then we tried brazing.

http://wess.freeshell.org/clausing/6...rning_down.JPG
http://wess.freeshell.org/clausing/6...wn_brazing.JPG

It looks like the crack filled but since gas welding didn't work I don't
feel like trusting it. There could be dirty metal in crack. So plan #2
forms.

I'll replace the hub by turning it off, boring and threading sheave for a
1045 steel hub followed by loctiting with 271 and driving two pins in mating
diameter.

Here is a drawing.

http://wess.freeshell.org/clausing/C...ave_repair.pdf

So last night I took a practice pass at threading to get my brain
configured. Compound at 29 degrees, crossfeed set at 0, infeed with
compound, hand on halfnut lever and pulling out and pulling up on lever at
end of thread.

I ended up blowing a pull out once. There wasn't a shoulder and if you
looked at drawing their will be one. The only other thing I can think of to
improve my chances is to put a dab of paint marker on shafting so I can have
a timing mark to pull out.

I'm open to suggestions on any other tricks to thread up to a shoulder, I've
already put in an undercut and the slowest speed is 45 rpm and the machine
is a Leblond servoshift so going out of gear at the last part and cranking
by hand isn't an option.

Thanks,

Wes