Grant Erwin wrote:

I'm making up a weldment in which the design calls for a continuous 2" of
internal threading. About 3/4" of it will be a threaded hole, and the rest will
be part of a rod coupler nut. I don't want the threads to bind. What I'm
thinking is to drill the 3/4" deep hole as though I were going to tap it, then
make up a scrap screw with the end 3/4" turned down to be a slip fit into the
tap hole, then use the scrap screw as an alignment tool to hold the coupler nut
centrally, clamp it tightly, weld it up, then remove the part to the hand tapper
and chase the threads in the coupler nut and use those to guide the tap to cut
the threads below.

I would just drill and tap the 3/4" hole and run my scrap screw in and screw on
the coupler nut, clamp it and weld it, but I've seen enough pieces move "just a
little" when welding to be leery. I don't want these threads to bind.

The threads are 5/8-11 so if they do bind, it could be really difficult to fix.

Ideas?

GWE

How about welding the coupler nut in place first and then drill the
pilot hole in the 3/4" stock using the coupler nut as a guide and then
finally run the tap through the coupler nut and through the 3/4" piece?
Might need a tap extension, but doing it in that order should insure
everything is in alignment.

Pete C.