I need to indicate an internal thread. It is a 2 1/4-8 thread and it
is on a backplate. Someone bored the register off center and I need to
bore and resleeve the backplate but the register bore has got to be on
the same centerline as the thread to make this work. I have the back
plate set up in the 4 jaw now I just need to figure out how to dial it
in so the bore and the thread centerline line up. Any suggestions
greatly appreciated. Thanks, Steve

"Steve" wrote in message
om...
I need to indicate an internal thread. It is a 2 1/4-8 thread and it
is on a backplate. Someone bored the register off center and I need to
bore and resleeve the backplate but the register bore has got to be on
the same centerline as the thread to make this work. I have the back
plate set up in the 4 jaw now I just need to figure out how to dial it
in so the bore and the thread centerline line up. Any suggestions
greatly appreciated. Thanks, Steve

Dial in the pitch diameter of the thread while the feed train is set up for
8tpi and engaged, so your indicator follows the thread as the chuck is
turned over by hand.

Ideally, your ball on the point of the indicator should be close to same dia
as a thread measuring wire would be for measuring an 8 tpi external.

--

SVL

I'm not sure exactly how accurate you need to be, but one time I needed to
do something like this, I turned a small piece of threaded rod down smooth
on one end in the lathe. I screwed this rod into the threaded hole and
indicated off the turned end.

To mount the threaded rod for turning, I placed a piece of bar stock in the
3-jaw chuck, and then bored and threaded it to the same thread. I then
tightened the threaded rod into this simple jig to hold it centered in the
chuck....or course doing all of this without unchucking anything.

I'm sure this isn't an exact method...but it worked very well in my
case...especially since the threaded hole I was working on was kinda small.
Not sure how well it would work for a larger hole like yours.

Todd

"Steve" wrote in message
om...
I need to indicate an internal thread. It is a 2 1/4-8 thread and it
is on a backplate. Someone bored the register off center and I need to
bore and resleeve the backplate but the register bore has got to be on
the same centerline as the thread to make this work. I have the back
plate set up in the 4 jaw now I just need to figure out how to dial it
in so the bore and the thread centerline line up. Any suggestions
greatly appreciated. Thanks, Steve

In article , Steve says...

I need to indicate an internal thread. It is a 2 1/4-8 thread and it
is on a backplate. Someone bored the register off center and I need to
bore and resleeve the backplate but the register bore has got to be on
the same centerline as the thread to make this work. I have the back
plate set up in the 4 jaw now I just need to figure out how to dial it
in so the bore and the thread centerline line up. Any suggestions
greatly appreciated. Thanks, Steve

One way is to make a tight fitting plug gage threaded the same
as the backplate. Leave a section sticking out that you
can indicate on.

Another approach (easier) would be to a) make a short
ring spacer to go over the register diameter on the spindle.
b) re-sleeve the backplate undersized. c) put the backplate
on the spindle, wrong-way-around, with the ring spacer in
place to allow it to bottom on the spindle.

Then bore the register diameter.

The first way would be more accurate, I think.

Jim


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