If the entire rifle is going to be re-blued, what’s the industry standard on installing an NEGC classic express sight with island base?

Solder plus drill and tap? Or is just soldering acceptable?

I’ve read about using loctite on banded front sights and barrel bands, but can loctite be used on a rear sight along with drilling and tapping?

I've not had any problem with the 8-36 screw

Right. They ain't going to fall off. Might be overthinking it. Just soldering is fine but you are left with holes in the base, unless you fill them with dummy heads. Can loc tite be used? Of course. I personally, just drill and tap and that's it.

In the spirit of if it's worth doing, it's worth doing to excess, I use both solder & screws.

Good point!

How deep does the hole need to be without getting too close to the bore? Is three or four threads sufficient?

Yes. I always try for .050 wall thickness left.

I put one of these rear sights on this past weekend on a 9.3x64. The wall thickness worked out to .245". So by drilling .130" deep that left enough wall thickness for me and left between 2 1/2 to 3 threads of screw engagement to hold the rear sight on.

As most of my jobs go out in the white to the customer, I tell them that after it has been blued to degrease the threads and use a medium thread locktite on the sight and scope base screws

J Wisner

Intregal is always best but expensive, I like screws and solder on my guns, see no reason not to..