I've got a Gillette "New Improved" Tuckaway, but the handle's cracked and won't hold together at all. The head is a nice shave, on a Fat Tech handle, so to repair the Tuckaway...
The handle top nut isn't threaded right the way, so first thread completely through.
Yep, right through. Nerve-wracking to do, harder than I'd have expected from brass.
Then the bottom part of the handle. The tube isn't cracked at the bottom, so the base plug is still firm.
Put it in the collet chuck. (Tighten enough that it won't spin and scratch the finish. But not so much that it damages the finish. Winding insulating tape over helps!)
Yes, it's in there! Now center drill.
And then drill, 4.5mm The base plug is quite thick (IIRC, 15mm, so can take a hole 8mm deep, meaning I can thread about 5mm).
Now I can screw a threaded M5 brass rod into the base plug, and into the top nut.
Mix some epoxy, dab the end of the threaded rod in it as a heavy duty threadlock. Cut rod to length, tip the rest of the epoxy down to help stabilise. Let set.
Mix more epoxy, dab on the other end of the rod, tip epoxy in, screw on top nut, leave to set head down.
No epoxy leaked! Bit heavier than before, but ready for use!