What is the correct tap drill size for a 3/4 X 16 UNF cap screw?

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Multiple Choice

What is the correct tap drill size for a 3/4 X 16 UNF cap screw?

When cutting internal threads, you drill a hole slightly smaller than the bolt’s major diameter so the tap can form the threads properly. For a 3/4-16 UNF screw, the standard tap drill size is eleven sixteenths of an inch. This size yields the correct thread depth for the 16 threads per inch UNF profile, giving adequate engagement without weakening the hole. Using a larger hole, like thirteen sixteenths or the full three quarters, would produce too shallow threads and weak engagement. A size such as twenty-three thirty-seconds is not the standard recommended for this exact size and would not give the correct fit.

When cutting internal threads, you drill a hole slightly smaller than the bolt’s major diameter so the tap can form the threads properly. For a 3/4-16 UNF screw, the standard tap drill size is eleven sixteenths of an inch. This size yields the correct thread depth for the 16 threads per inch UNF profile, giving adequate engagement without weakening the hole.

Using a larger hole, like thirteen sixteenths or the full three quarters, would produce too shallow threads and weak engagement. A size such as twenty-three thirty-seconds is not the standard recommended for this exact size and would not give the correct fit.

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