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UNC / UNF Tap Drill Size Chart
The tap drill for every inch machine screw thread – coarse (UNC) and fine (UNF). Read the table or tap any size for its full reference page.
UNC & UNF tap drill chart
| Thread | System | Tap drill | inches | mm |
|---|---|---|---|---|
| 1/4-20 | UNC | #7 | 0.201 | 5.105 |
| 10-32 | UNC | #21 | 0.159 | 4.04 |
| 8-32 | UNC | #29 | 0.136 | 3.45 |
| 10-24 | UNC | #25 | 0.1495 | 3.8 |
| 6-32 | UNC | #36 | 0.1065 | 2.71 |
| 5/16-18 | UNC | F | 0.257 | 6.53 |
| 3/8-16 | UNC | 5/16 | 0.3125 | 7.94 |
| 5/16 | UNC | F | 0.257 | 6.53 |
| 3/8 | UNC | 5/16 | 0.3125 | 7.94 |
| 1/4-28 | UNF | #3 | 0.213 | 5.41 |
| 1/4 | UNC | #7 | 0.201 | 5.105 |
| 1/2-13 | UNC | 27/64 | 0.4219 | 10.72 |
| 1/2 | UNC | 27/64 | 0.4219 | 10.72 |
| 5/8-11 | UNC | 17/32 | 0.5313 | 13.49 |
| 3/4-10 | UNC | 21/32 | 0.6563 | 16.67 |
| 7/16-14 | UNC | U | 0.368 | 9.35 |
| 5/16-24 | UNF | I | 0.272 | 6.91 |
| 3/8-24 | UNF | Q | 0.332 | 8.43 |
| 4-40 | UNC | #43 | 0.0890 | 2.26 |
| 1/2-20 | UNF | 29/64 | 0.4531 | 11.51 |
| 5/8 | UNC | 17/32 | 0.5313 | 13.49 |
| 7/16 | UNC | U | 0.3680 | 9.35 |
| 1-1/4 | UNC | 1-1/8 | 1.1250 | 28.58 |
| 12-24 | UNC | #16 | 0.1770 | 4.50 |
| 2-56 | UNC | #50 | 0.0700 | 1.78 |
| 6-48 | UNF | #32 | 0.1160 | 2.95 |
Most popular sizes
The most-searched inch sizes – jump straight to the ones machinists look up the most:
Drill bit size guides
Dedicated pages for the individual number and letter drill bits – each shows the bit diameter in inches and mm and the thread it drives:
#7 Drill Bit
0.2010 in · 1/4-20 tap drill
#21 Drill Bit
0.1590 in · 10-32 tap drill
#29 Drill Bit
0.1360 in · 8-32 tap drill
#30 Drill Bit
0.1285 in
#25 Drill Bit
0.1495 in · 10-24 tap drill
#10 Drill Bit
0.1935 in
#8 Drill Bit
0.1990 in
F Drill Bit
0.2570 in · 5/16-18 tap drill
#3 Drill Bit
0.2130 in · 1/4-28 tap drill
#36 Drill Bit
0.1065 in · 6-32 tap drill
#16 Drill Bit
0.1770 in · pilot & clearance