Tap drill size calculator
Pick a SAE or metric thread size and get the recommended tap drill for ~75% engagement — interactive, with the handbook chart source cited.
Recommended tap drill
#7
≈ 0.2010″
For thread 1/4-20 UNC
Values target ~75% thread engagement. Confirm against your tap manufacturer’s chart for the exact tool.
Search “tap and die set” on Amazon(affiliate link)
Opens Amazon.ca search results — not a confirmed product fit. Verify with the seller before buying.