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Old 25th Jun 2021, 5:38 pm   #6
GrimJosef
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Join Date: Sep 2007
Location: Oxfordshire, UK.
Posts: 4,310
Default Re: Tapping a hole in metal: What size hole?

Quote:
Originally Posted by SiriusHardware View Post
... it seems that the general answer is that you do NOT use a drill which equals the 'M' size of the tap / screw to be used ...
Yes. The tapping drill is smaller by an amount that depends on the thread profile. If you use a drill larger than this then the screw will be loose. If you use one smaller then there is an increased risk that the tap will snap as you try to cut the excess metal away. Of course for this to work properly you need to drill the tapping hole carefully. A drill press will ensure that the bit runs true. If you have to use a hand-held drill (either powered or hand-turned) then there's a real risk of wobbling and the final hole turning out larger than it should.

Cheers,

GJ
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