I have never tapped or threaded any material before, and therefore I would lke to ask for advice on the following:

I have two 40mm rods. I would like to externally thread about one inch of one rod, and corespondingly tap one inch of the other rod so that the two rods screw together. S my questions are these:

I) What size drill bit do I need to use to drill the hole prior to tapping?

ii) What size tap do I need to buy?

iii) What size die do I need to buy?

Your help will be greatly apreciated.


Kind regards,

MG

40mm, 1 5/8" or so, is pretty big to try and tap and cut an external thread, particularly a machine thread. You won't be able to do it without reducing the size as the thread on the internal tap would cut through the rod wall. Why not drill smaller holes on the centers, 10,12 or 13mm machine thread, tap both and then join them with a smaller threaded rod?