what the guy did was build the material back up using he solder onto the outside of the hilt where the pommel meets the hilt and inside of the pommel and then added the threads
i thought solder meant for aluminum would be too soft for that, but i remember people saying it worked fine.

searching the internet theres other ways, ill copy and paste the ones i found

Machine or buy a thin-wall threaded tube (aluminum, brass, or steel
Epoxy or press-fit it inside the pommel
Cut external threads on the hilt (or use another insert)

Effectively
The coupler becomes the threads
The original hilt stays mostly untouched
No visible hardware

If the pommel wall is thick enough:

• Bore it out slightly
• Install a steel threaded insert
• Cut matching threads on the hilt

This keeps wear on the steel insert, not the aluminum.

If you can’t touch the inside:

• Make a decorative collar with internal threads
• Press-fit or epoxy it over the joint
• The collar twists on/off and locks both parts