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#5-44 tap drill size
Use a #37 drill (.1040 in / 2.64 mm) to tap #5-44 UNF. That gives about 71% thread engagement. Closest metric drill: 2.6 mm.
#5-44 thread specifications
| Thread | #5-44 UNF (fine) |
|---|---|
| Major (nominal) diameter | .1250 in / 3.17 mm |
| Threads per inch | 44 (pitch 0.577 mm) |
| Theoretical drill for 75% thread | .1029 in (2.61 mm) |
| Recommended tap drill | #37 = .1040 in |
Alternative drills and % of thread
Any of these drills will tap #5-44. Smaller drills give more thread but make tapping harder and raise the risk of breaking the tap, especially in stainless steel and in small sizes. 60–65% thread is common in tough materials. 75% is the general-purpose standard.
| Drill | Inch | mm | % thread |
|---|---|---|---|
| #38 | .1015 in | 2.58 | 80% |
| #37 | .1040 in | 2.64 | 71% |
| #36 | .1065 in | 2.71 | 63% |
| 7/64 | .1094 in | 2.78 | 53% |
| #35 | .1100 in | 2.79 | 51% |
Tips for tapping #5-44
- Use cutting fluid, and with a hand tap back off about half a turn every turn or two to break the chip. Aluminium and soft materials are the exception: they tap cleanly with spiral-point taps.
- For blind holes, drill deeper than the thread you need. Allow at least 3–4 pitches beyond the last full thread for a plug tap (0.091" for 44 TPI).
- Thread engagement of 1–1.5 × the diameter (3.2–4.8 mm) is enough for most steel parts. Softer materials need more.