"davenpat" wrote in message ...
"N. Thornton" wrote in message
om...
Harry Bloomfield wrote in message
o.uk...

What can happen with a quality drill, is that the tip changes colour and the
cutting edge gets rounded. The result is a hot drill. The cause is too fast
rotation or lack of push to keep the drill drilling. Or both.

The
result is that one has to go slow to avoid blunting the thing while
drilling just ONE hole. Yes I've done it. Even on wood I've had bits
that have got smoking hot and lost their cutting ability.

Wrong drill angles, that's all that was wrong.
Drill angle depends on the material to be drilled. Change the material and
you change the drill angles to those that work best.

I suspect thats the key to all this. Twist drills are generally
multipurpose, which means their angles are wrong for almost
everything. For wood theyre terrible.

Along comes my a with a steeper angle, its better matched and sails
through. But presumably it would not do well on harder materials like
stone, concrete and iron. But for the things I use them for they do
well.


Regards, NT