Thread: Tap drill size
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James Waldby[_3_] James Waldby[_3_] is offline
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Default Tap drill size

On Fri, 10 Jul 2020 15:43:04 -0700, Christopher Tidy wrote:

Hi folks,

Can anyone tell me the correct drill size for use with this tap?

https://www.ebay.com/itm/15-32-32-GH...AOSwpnRe86N k

I am guessing 7/16" or very close, but does anyone know for sure?


In metric the tap would be 11.9 x .794 mm; charts like at
https://www.victornet.com/reference/Tap_Drill.html show
11.25 mm drill for 12 x 0.75, and taking off 0.1 mm would
give 11.15, which is 0.0015 over 7/16". The metric calculator
at http://theoreticalmachinist.com/TapDrillSizeCalculators
gives 11.20 for a 12 x 0.8 mm thread at 77% thread.

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jiw