"Frank Erskine" wrote in message
...
On Sat, 1 Apr 2006 08:06:39 +0100, Cordless Crazy
wrote:


If I want to form a M8 thread in a piece of sheet steel, what size hole
do I initially drill?

I am thinking 2mm less or is that too much?

Would that make it a 6mm hole?!?

6.8mm is the correct size, according to "Machinery's Handbook".

--
Frank Erskine
Sunderland

===================
My chart shows some variation depending on the pitch of the thread.

Fine thread (0.75) - 7.2mm drill, medium thread (1.00) - 7mm drill, coarse
thread (1.25) - 6.8mm drill. If you're not sure what the pitch is it would
be sensible to start with the smallest hole and if the tap binds go to the
next larger drill hole.

Cic.