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DIY & Home Improvement

Nittersing

(7,028 posts) Sun Apr 14, 2024, 09:34 AM Apr 2024

Need help understanding tap & die sizes [View all]

I have a piece of acrylic that is 5/16" (?) thick.

I want to tap four holes for screws with 1/4-20 thread

I believe the drill size I need to use is a #7.

But I can't figure out the tap size. I don't see any numbers that reference 1/4-20.

I have both metric and sae...

What am I not understanding?

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11 replies

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Need help understanding tap & die sizes [View all] Nittersing Apr 2024 OP

1/4-20 tap must be missing from your set. amerikat Apr 2024 #1

OK - found it... nt Nittersing Apr 2024 #6

yes, a number 7 drill is correct, BUT... ret5hd Apr 2024 #2

Good tip about a smaller drill hole. Thanks. nt Nittersing Apr 2024 #7

Do you think a drill guide is worth it? Or is it mostly hype? Nittersing Apr 2024 #9

i won't speak to that... ret5hd Apr 2024 #10

and that item IS NOT what you need... ret5hd Apr 2024 #11

You are on the right track. 1. look closer at the tap. 2. look for an accompaning chart that details the layout of the.. usaf-vet Apr 2024 #3

This is how I finally found it... matching up the threads Nittersing Apr 2024 #8

Do. NOT. essaynnc Apr 2024 #4

I was surprised to see that there's a choice of tap drill sizes for 50% and 75% thread engagement. usonian Apr 2024 #5