by david
(mooresville nc USA)
What size tap is used to tap a hole for a 1/4 inch air fitting?

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Tap fitting size?
Hmmm, not trying to be funny here. I would just select a 1/4″ NPT tap for a 1/4″ NPT fitting thread.
Or am I missing something in your question, David?
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1/4 inch tap
by: Buster
I agree with you Bill, haha.
He may have meant what drill bit size he needs to tap a 1/4 inch NPT thread, which would be 7/16″.
1/4 inch pipe quick connects can have different sizes of connections for different sizes of pipes, from 1/8″ pipe up to 3/4″ pipe thread with the most common being 1/4″ NPT.
Just a thought!!
Have a great day David!!!
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By Bill
If you google tap / drill size you’ll find many charts. Here’s one: https://www.lincolnmachine.com/tap_drill_chart.html .