Just checking- so you've got something like a stunt saber with a 3/8'' threaded rod through it and the pommel you've got for it has a threaded hole smaller than 3/8'', is that correct?
If so here's how I'd probably go about it- allowing for the fact that I don't physicaly have it in my hands to make a decision, which can always change things as you can correct things on the fly.
Here's what you'll need-
A 3/8'' starting tap and a finishing tap and handle to suit-
You'll need to find out if your thread is UNC (a
Coarse thread- wide gaps between the threads) or UNF (a
Fine thread- small gaps between the threads). Take the rod to your hardware when buying the taps they'll be able to tell you which you've got.
Taps can come individually or as a set of three with a- starting, intermediate and finishing tap. All you really need is the starting and finishing taps in most cases (but it may be cheaper to buy the set rather than just the two). You'll need the starting tap to start off your thread as the start of it cuts a very shallow thread and gradually increases to the full thread size.
You'll also need a finishing tap as I'm assuming you have a "blind hole" meaning that the hole doesn't go all the way through the pommel. The finishing tap (or bottoming tap) doesn't have that shallow cut at the start and will give you a nice full thread almost all the way to the bottom of the hole.
Some cutting fluid-
Some light oil would probably do in your case if your pommel is aluminium.
A drill bit to suit the hole you need-
3/8'' UNC should be an 8mm and a 3/8" UNF should be a 8.5mm drill bit.
But check with the person at the hardware when you get the taps.
Depending on the size of your exsisting thread you may need to fill the old thread in. This depends on wether or not there will be any of the old thread left when you drill the hole for the 3/8" tap and how much. If the drill gets rid of most of it then it'll be fine just to tap over it and form a new thread. If not than the 3/8'' thread you form probably won't have enough meat for your rod to bite into and you may have a sloppy fit or no fit at all. Some metal repair putty would be the easiest fix for that and is quite in expensive. You just knead the two compounds of the putty together and fill in the old thread, let it set, tidy it up with the drill and do your new thread.
What to do-
Put your pommel in a vise-
Use something soft but firm around your pommel so the vise jaws don't damage it. Some aluminium is usually best but some leather or something similar would also do.
Make sure you've got it set in there straight and at a comfortable height to work with when you're drilling. The more preperation you do the more you're likely to get it right on the first go.
Use a square (as in a machinist or carpenters square) or anything with a right angle to help you line the drill bit up straight for drilling. If you don't drill straight then your thread won't be straight and the pommel will be ****** to one side.
Make sure not to drill too far! mark the depth that you want the drill to go by putting some masking tape around the drill bit at the correct length- a simple and easy trick that I love using.
When tapping use a bit of cutting fluid or oil to help prevent the tap from binding. Once the tap starts biting into the metal take a step back and use the same square/right angle to check you're tapping straight, check from two angles. If not you can correct it still at this point as the starting tap has only made a shallow cut into the material and is easy to straighten up. Every half a turn or so back it off- reverse it. This breaks the swarf that you're cutting off and helps prevent the tap binding and breaking on you which is a MAJOR pain in the arse to deal with. Take your time and reverse every half tun or so, don't forget this!
Once you've done the starting tap do the same thing again with the finishing tap. And then you're done!
Sorry I've been so long winded but I hope that explains how I'd go about it clearly and is of some help to you SirJediKnightTim. let us know how you go.
