I picked up a few IHMSA rear sights for the T/C Contender. The stock
elevator stem has a crude black finish that is not hard. Its already
wearing away in the dovetail.

I did some Super High Intensity Tinkering, and found out that you can
open the base dovetail and the elevator stem of a Williams FoolProof
fits right in.... However, there is a problem, as the IHMSA sight
(possibly T/C made investment casting) uses a 6-40 thread, and the
Williams FP uses a 6-48 thread. Result- the elevator screw makes about
three turns, then everything stacks up.

I picked up some stainless steel hypodermic tubing, .148 OD and .110 ID
to thread internally. Drill out the existing thread, then press in the
threaded tubing. Waa-laa, correct thread.

Sight base is steel (suprise!)
Web thickness around existing internal thread is @.200"

The tubing comes out as .1475 OD on my Starret. The load will be light,
just the elevator stem. What should I drill the existing thread out with
(diameter) and follow up with a reamer (diameter)?

I dimly remember a drill should be about .005" under the diameter of the
reamer.

What should the final diameter be for a press fit?