Hi Guys

I need to tap a 1/2 BSP hole in an alloy rocker covet I have. I have seen some taps on ebay but am confused as to what i need - bottom, tapered etc. What exactly do i need? The part i want to screw in isnt tapered if it helps.

Also, what size hole will I need to drill to tap 1/2" BSP?

Thanks
Shaun

Taps are available in carbon or high speed steel (HSS) and in sets of 3. Taper or first tap, second and finally plug or bottoming tap. You will need a fairly hefty tap holder for that size.

A carbon steel tap should be fine except if you are tapping stainless and then you will need HSS which cost a bit more. Normally one would drill a hole of the correct size given here:
http://homepages.tesco.net/~a10bsa/bspgo.htm
Use the taper tap first which might be sufficient if you are not tapping a blind hole or don't need the thread to reach the bottom of the hole.

Hope this helps

Yeah, basically you start with a tapor, then do a intermediate, then a bottoming for a full job on a blind hole.

However if your not taping a blind hole you dont need a bottoming tap, and if its fairly thin with plenty of space the other side you can do it all with a tapor.

I have also used a intermedate only on alumium with care. Not advised with smaller taps!


Daniel

Thanks guys - I the alloy is make 10mm think so I have ordered a 19mm drill bit nd a pair of taps - hopefully I will be ok!

Shaun