Don Foreman wrote:
On Wed, 24 Aug 2005 18:27:40 -0700, 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


Have a design review with the requestor.

3/4" of thread will contribute about zilch to the strength beyond the
1.25" thread length of the coupler nut with 11 pitch thread.

Make a clearance hole in the 3/4" material, let the ample thread of
the rod coupler nut bear the load, no worry about aligning threads.

Um, the threaded piece that goes through this hole is only 1" long.

GWE