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tap drill size for acme taps.

this page is for information only

link to Acme Tap page

tap drill size for acme taps

Based on a 100% of thread as per ANSI

to calculate tap drill size for acme taps.

the magic formula

step 1

1 Divided by TPI ( threads per inch)

step 2

subtract this amount from the OD.

for pitches 10 and greater always add .005" for the drill size.

for pitches less than 10 TPI take the amount from step 1 and multiply x.05 ( 5 %) and add this to the drill size.

This is for 95% to 100% threads.

eg 1/2-10

1/10 = .100 ( step 1 )

.500 ( the OD ) minus .100 ( from step 1) = .400 drill size.

since the pitch is 10 or greater add .005" so the drill size is .405"

eg 3/4-6

1/6= .167"

.750 - .167 = .583" ( 100% )

.167 X .05 = .008" ( to obtain 5% )

.583 + .008 = .591" ( 95%)

thanks to Mack from Widell

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• ACME Thread Designer Program
Type in the nominal size and threads per inch for your ACME thread and get all the needed min and max diameters for your machine drawing.

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updated Aug 2007 , Apr 2004
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