Ig,
pipe threading requires an enormous amount of torque. Flat vice jaws
haves too
little surface contact.
Try making this tool I have several sizes of.
For 1/2" pipe (.840" OD) clamp two 3" pieces of 1" aluminum bar
together with .015"
shims between them. Drill thru the joint 27/32" long ways. With any
luck this with
make a saddle clamp with allmost 100% contact. Now put your pipe in
this tool and
into the 4" vise and try the threading die.
This tool is also great for screwing/unscrewing nipples without
damage.
RichD, Atlanta