In article ,
PrecisionMachinisT wrote:

"Ignoramus9727" wrote in message
...
If I want to tap a hole for 1/2"-20 threading, what hole size should I
use? thanks

i

Suggest download a chart.......

http://www.google.com/search?hl=en&l...rt&btnG=Search

Or, if you have a drill index by HUOT, there is usually a chart
for tap drill and clearance drill for common threads. Not sure whether
there is anything as fine as 20 TPI for 1/2", however. The index is
downstairs, and I am not. :-)

Of course, _Machinery's Handbook_ has all the tables you could
ever need.

Good Luck,
DoN.
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