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Drill Rod sizes vs. Drill/Reamer sizes

Glenn Wegman

Hot Rolled
Joined
Jan 6, 2007
Location
Florida
I was making small diameter pins from Drill Rod (not drill blanks) and needed a reamer to fit them so I headed for the MSC Catalog.

It turns out that #10 Drill Rod (W-1, 0-1) is .191", but a #10 Drill or Reamer is .1935, but a #11 Drill or Reamer is .191".

What's up with that?
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For some silly reason I thought that #10 Drill Rod would be the same size as a "10 Drill or Reamer!

Upon further investigation, very few of the designated drill rod sizes for wire sizes coincide with designated equivalent drill/reamer sizes. I've checked every catalog I can find, all with the same results. Fractional and Letter sizes all coincide.

Anyone know why that is?

Glenn
 
A little more research in Machinery's Handbook yielded this:

Drills are sized to ANSI B94.11M-1979,R1987

Fractional and Letter size Drill Rod is apparently sized to the ANSI standard above.

Wire size Drill Rod is sized to Stub's Steel Wire Gage sizes which range from #1 to #80 which is similar in designation to Wire Size drills (1 thru 92?) which are sized to the ANSI Standard above.

Apparently, from what I could find, there are at least six different wire gage standards that all use number designations but have differing decimal sizes.

Makes perfect sense........right?
Must have been an Engineer involved
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Thanks,

Glenn
 








 
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