Installing an old mortise lockset into a front door. Lockset was purchased (quite pricey with door knobs, cover plates etc.) from a restoration hardware place. They reconditioned all the parts and patinated (sp?) them all to look similar.

Problem: The threaded lock cylinder needs to be fixed from rotation with a radially applied screw that is over 2-1/4 inches long. The existing threads in the bronze casing is 8-32. I have three choices:
1) Find a screw of the proper length and 8-36 thread with a fillister head
2) Find any long 8-36 screw and turn down the head to fit the hole
3) Re-tap the threads for 8-32 which opens a whole world of screws.

The problem with option 3 is that all of my 8-32 taps (I have over 50) are about a 1/4 to a 1/2 inch too short. Have any of you successfully lengthened an existing tap? I have mig, tig & oxy but am worried about axial alignment on the tap extension.

What are the probable result of re-tapping an 8-36 to an 8-32 in bronze? Will I end up with a crappy loose thread fit?

BTW, tried McMaster-Carr and Fastenall. At McMaster I cannot find 8-36. At Fastenall, I do find 8-36 but maximum length is 1-1/4 inches. I would need to buy quantity 100 but at least I would get to practice my screw-lengthening skills which should be easier than tap-lengthening.

All advice appreciated.

Ivan Vegvary