Tapping Copper
 

I have begun two blocks and with both I have broken the taps off when trying to thread the block so one will be a NB block but I will have to tap that too. Is there some thing I am missing with tapping copper? Why are they snapping off? I'm using taps that have four channels too, used em in stainless and aluminum with 0 problems :shrug:

Using a T handle?

Lubrication?

1/2 turn forward, 1/4 turn back to clear the threads?

Tapping copper is horrible with small taps. Typically anything 6-32 or smaller is really hard with regular taps.

For one, make sure your doing what uberblue is doing,
secondly. if you got a lot to tap, get ahold of some thread forming taps, also called cold forming or fluteless. They use a little larger hole and you can virtually turn them all the way through the material with a little oil. The only downside is that there isnt as much of threads there. Close but not quite as much. They are typically a little stronger than the same amount of thread with a cutting tap becasue the metal is being pushed and not cut.

I use a 4-40 tap and a #38 drill and I have tapped probably over 100 holes with the same tap. about 90% being in copper.

They can be found at mcmaster, jtsmachine.com and many other places. dont expect to find them locally.


Jon

I have found that drilling the tapping hole slightly larger than specified (ie 0.2mm) works well in the soft copper. The slightly larger hole allows the tap to go through with a little less difficulty, yet still cuts a strong thread.

Arc

Slow, slow, and slower. Uberblue got it right. You cannot do a full turn into copper. Copper is very soft and very dense. The material does NOT remove as well as aluminum. Slow with WD-40 or similar.

Exactly, and if it is thick you are going to clog the debris channels pretty quickly. This means you will be forced to remove the tap completely and clean it out, re-lube it up, and go in again. Be careful with a T-handle: you can put a lot of torque on a tap, a bad thing with a smaller tap. This means you have to "feel" the tap and look at it to be sure it isnt flexing. If you see much flex, back off and try again. Also, if you get stuck and the thing is jammed in there and wont go any farther, back it off and drill it again: you might just have something stuck in there.

And yes, using larger bits does work as long as the holes do not need to be blocking water or holding a signinficant load.