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Author Topic: What is the correct Drill size for 3/8" NPT tap?  (Read 5496 times)

Offline ChuckMC8

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What is the correct Drill size for 3/8" NPT tap?
« on: May 04, 2006, 03:06:22 AM »
 Does anyone have a chart that tells which drill bit size to use before a 3/8" NPT tap? It usually sez on the tap,but thisone doesnt have it inscribed.Thanks, Chuck L.
Far better is it to dare mighty things,to win glorious triumphs,even though they may be checkered by failure, than to rank with those poor spirits who neither enjoy nor suffer much,because they live in the gray twilight that knows neither victory nor defeat.  Theodore Roosevelt (1858-1919)

Offline Ednj

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Re: What is the correct Drill size for 3/8" NPT tap?
« Reply #1 on: May 04, 2006, 03:48:22 AM »
To answer your question 3/8 – 18 npt = 19/32
.
Here’s some info.
.
NPT National Pipe Thread
Tap size. Threads per inch. Drill size.
1/8              27                          11/32
¼                18                            7/16
3/8              18                            19/32
½                14                             23/32
¾                14                             15/16
1                  11-1/2                      1-5/32
1-1/4           11-1/2                       1-1/2
1-1/2            11-1/2                      1-23/32
2                   11-1/2                      2-3/16
2-1/2              8                             5-5/8
 
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Offline ChuckMC8

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Re: What is the correct Drill size for 3/8" NPT tap?
« Reply #2 on: May 04, 2006, 04:12:01 AM »
Thanks Ed.     
Far better is it to dare mighty things,to win glorious triumphs,even though they may be checkered by failure, than to rank with those poor spirits who neither enjoy nor suffer much,because they live in the gray twilight that knows neither victory nor defeat.  Theodore Roosevelt (1858-1919)