[TowerTalk] drilling chrome-moly mast

[john at kk9a.com]

Yes this is good advice. It is also much easier to push a hand drill using
this method and the bit is less likely to walk off center.  The drill may
try to jam if you increase the size in small increments. I personally
approximately double the size with each cut, for example if I wanted a Ø3/8
hole and was using a hand held drill, I might start with 3/32, than 3/16 and
then 3/8. Because the smaller starting bit has less circumference you need
to run that drill bit significantly faster to maintain the proper surface
feet per minute of cutting or you will break it, which is no fun on the
tower.

John KK9A

From:	Warren Munro <wmunro1 at hawaii.rr.com>
Date:	Tue, 28 Aug 2018 15:29:03 -0400

>
All:

This may have been mentioned before, but my machinist brother-in-law advises

drilling starting with a quite small bit and then use new gradually larger
bits 
as you step up in hole size. This will cut down on the annealing, and will
help 
eliminate the "bite" at the end of the final hole.

73

Warren    KH6WM