Here's the actual process:
As above grind away as much of the rivet inside the slide as possible.
Put the slide on a padded bench block with the sight over the edge.
Use a punch to carefully tap the old sight out until it either falls free, or can be gripped with a pair of Vise-Grips and pulled out.
Clean up the sight area.
Determine whether you have the old style narrow sight tenon, or the new style wide.
The wide tenon is the same width as the sight.
Use a 1/4" Dremel carbide ball cutter to cut a small shallow "crater" or countersink around the sight's hole in the INSIDE of the slide.
This countersink gives the new sight's rivet a place to flow, so that later there's enough left to hold the sight.
Test fit the sight's tenon to the slide.
Use a solvent like acetone to degrease the slide and sight.
Apply a coat of Loctite Red to both sight and slide.
Fit the sight in place, rest it on a brass padded bench block and use the riveting tool to flair the sight tenon, making sure to flow the rivet down into the countersink you ground.
During riveting, make sure the sight remains level.
After firmly riveting the sight, use a Dremel tool with rubber abrasive tips to grind away JUST enough rivet to allow it to clear the barrel bushing.
DO NOT allow the sight or slide to get hot during grinding.
Once the rivet is flush enough to clear the bushing, allow to stand for 24 hours for the Loctite to cure, then use hot soapy water to clean off the excess.
Touch up with cold blue if desired, and apply a good rust proofing lube to prevent rust.
The "Secret" is the countersink in the slide to give the rivet room to flow.
Many people just rivet the tenon over the flush slide, and when they grind off the excess to clear the barrel bushing, they grind off most of the rivet from the curved slide surface.
Without enough rivet, the sight soon loosens up.
