#5-44 UNF tap drill size
Use a #37 drill (0.1040 in, 2.64 mm) for #5-44 UNF. It is the standard chart size and leaves about 71% thread, enough for full practical strength without excessive tapping torque.
| Drill | inch | mm | Thread % | Typical use |
|---|---|---|---|---|
| #40 | 0.0980 | 2.49 | 91.5% | Tight: high tapping torque, tap breakage risk |
| #39 | 0.0995 | 2.53 | 86.4% | Tight: high tapping torque, tap breakage risk |
| #38 | 0.1015 | 2.58 | 79.6% | General purpose |
| #37 (chart drill) | 0.1040 | 2.64 | 71.1% | General purpose |
| 2.65 mm (metric drill) | 0.1043 | 2.65 | 70.0% | General purpose |
| #36 | 0.1065 | 2.71 | 62.7% | Hard or tough material, deep or blind holes |
| Thread | Tap drill | Tap drill (mm) | Clearance close / free |
|---|---|---|---|
| #3-56 UNF | #45 (0.0820 in) | 2.08 mm | #37 / #35 |
| #4-48 UNF | #42 (0.0935 in) | 2.37 mm | #32 / #30 |
| #5-44 UNF (this page) | #37 (0.1040 in) | 2.64 mm | #30 / #29 |
| #6-40 UNF | #33 (0.1130 in) | 2.87 mm | #27 / #25 |
| #8-36 UNF | #29 (0.1360 in) | 3.45 mm | #18 / #16 |
Practical notes
Spiral-point taps suit through holes; spiral-flute taps lift chips out of blind holes. In a blind hole, drill a few threads deeper than the full-thread depth you need.
Typical engagement lengths: about 1 × diameter in steel, 1.5 × in cast iron or brass and 2 × in aluminium. In tough stainless or hardened steel a slightly larger drill (60–70% thread) cuts torque and tap breakage with little loss of strength.
Thread-forming (roll) taps need a larger hole, roughly 0.1136 in (2.89 mm, D − 0.5 × pitch). Check the tap maker's chart; forming suits ductile metals such as aluminium, mild steel and brass, not cast iron.
UNF (fine) threads have more threads per inch than UNC, a larger tensile stress area and better resistance to loosening, but they strip more easily in soft material and are more sensitive to drill size.
Clearance drills for a #5 screw: close fit #30 (0.1285 in, 3.26 mm), free fit #29 (0.1360 in, 3.45 mm).
FAQ
What size drill for a #5-44 UNF tap?
The standard tap drill for #5-44 UNF is a #37 drill, 0.1040 in (2.64 mm), which gives about 71% thread.
What clearance hole for a #5 UNF screw?
Use #30 (0.1285 in, 3.26 mm) for a close fit or #29 (0.1360 in, 3.45 mm) for a free fit. Clearance depends on diameter only, so it is the same for UNC and UNF #5 screws.
What metric drill can I use for #5-44 UNF?
The closest metric drill is 2.65 mm (0.1043 in), giving about 70% thread on #5-44 UNF.
What is the difference between #5-44 UNF and #5-40 UNC?
Both are #5 diameter. #5-44 UNF has 44 threads per inch and uses a #37 tap drill (0.1040 in); #5-40 UNC has 40 TPI and uses a #38 drill (0.1015 in). The threads are not interchangeable.
Sources: ASME B1.1 — Unified inch screw threads (UN and UNR form) · Machinery's Handbook — tap drill sizes and percentage-of-thread formula · ASME B94.11M — twist drills (number and letter drill sizes) · Common machinist clearance-drill chart (close / free fit)
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