Usual rule of thumb is that nut is stronger than the bolt when the nut
thickness is .7 x the bolt diameter. This varies with various grades of
bolt but it is a good start. So any thread length over 1/2" is not doing
anything useful.

Grant Erwin wrote:

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