I think it would be costly to buy a tap that size and you would also need a
large machine . But there are shops
that do nothing but cut threads. Any kind you can think of. And most machine
shops can cut threads. Look in Yellow pages under threads or threading.
I used to use Vescio Threading in Santa Fe Springs Ca
And they had a ton of threading machines maybe 50
of them and I think they also ground threads.
Jim
"Bernard Arnest" wrote in message
ups.com...
Hi,
I was wondering if it would be possible to tap the interior of a ~4"
diameter pipe? I can't imagine a tap so large...? Can I tap it on the
lathe, by somehow getting the cutterhead inside (I'll need to go back
to the shop on Monday to assess if it can)...? If not, are there
places that will economically tap it for me? Or, just rethink my
design to not require this; although it just makes the design better if
I can do it.

Secondly, is there a way to tap for acme-style threads; are such
threads preferred for higher-load applications like bringing together
to vise jaws?


thanks!
-Bernard Arnest