tap drill size

[porthos]

what drill size for a 7/32-40 tap??

 

[Rooster]

Greetings, a 7/32-32 is a #12 so a 7/32-40 is most likely a #10

 

[CluelessNewB]

Online calculator: (also says #10)

http://theoreticalmachinist.com/TapDrillSizeCalculators

 

[RJSakowski]

Subtract the thread pitch in inches (1/tpi = .025) from the major diameter (7/32 = .219") for .194". This will give you about a 70% thread. A #10 drill is .193" and a #9 drill is .196". Either should work fine.

The formula works for all 60º threads.

 

[Tinkertoy1941]

The old tool makers used this formula.
Hole Size for 3/8 16 tap = Diameter .375 minus the reciprocal of the pitch 1/16 =.0625 = .375-.0625= Tap drill .3125
This will work for all threads.
This can also be found in The Henry Ford Trade school books!

 

[kd4gij]

Or download Drill Bit charts free for your phone. Nice app I use it all the time








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[Tinkertoy1941]

Use your phone and tell me the hole size for a 2.375Diameter 12 pitch Left Hand thread.

 

[Bi11Hudson]

It would be (2.375) minus (1/12) in inches. The handedness of the screw is not a relative factor.

 

[Tinkertoy1941]

You are correct!!