On Oct 31, 3:24 pm, Jon Elson wrote:
rodjava wrote:
On Oct 31, 9:51 am, rodjava wrote:
Hi,
I would like to replace the threaded nose cap for my 10L SouthBend
lathe spindle.
It has a 2 1/4 - 8 threaded spindle. What size should I bore the
minimun hole for threading internally?

If somebody can reffer me a link where I can find the information
myself, that would be great too.

Thank you all in advance.

Rod

I found the answer to my own question hehttp://www.newmantools.com/tapdrill.htm#callink
BTW, its 2.128215 for a 75% thread percentage

Can you really machine to 1 micro-inch on your 10L? That's pretty good!

Jon



No need for 6 decimal place dimensions he-))

The rule of thumb that withstood the test of time is, for any 60
degree screw thread:

Tap drill diameter = major diameter - pitch of thread. For the thread
at hand we have:

2 1/8" tap drill diameter = 2 1/4" - 1/8" . Small adjustments may be
made for tough materials (make this hole bigger) or soft materials
(make hole smaller). Thread pitch = 1 / threads per inch.

Machinerys Handbook, any edition, is your friend for information like
this.

Wolfgang