# 10-32 tap drill size

URL: https://www.clove3d.com/tools/tap-drill/10-32/

Tap drill for 10-32 UNF: #21 (0.1590 in / 4.04 mm), about 76% thread.

## Thread specs

- Series: UNF
- Major diameter: 0.1900 in
- Pitch: 32 TPI
- Basic minor diameter: 0.1562 in

## Every drill that works (50-85% thread)

| Drill | % thread | in | mm | Good for |
|---|---|---|---|---|
| #18 | 51% | 0.1695 | 4.31 | deep holes only |
| 4.3 mm | 51% | 0.1693 | 4.30 | deep holes only |
| #19 | 59% | 0.1660 | 4.22 | deep holes only |
| 4.2 mm | 61% | 0.1654 | 4.20 | hard or tough metals |
| 4.1 mm | 70% | 0.1614 | 4.10 | general use |
| #20 | 71% | 0.1610 | 4.09 | general use |
| #21 (standard) | 76% | 0.1590 | 4.04 | general use |
| 4.0 mm | 80% | 0.1575 | 4.00 | more torque, more broken taps |
| #22 | 81% | 0.1570 | 3.99 | more torque, more broken taps |
| 5/32" | 83% | 0.1563 | 3.97 | more torque, more broken taps |

## Clearance hole

- Close fit: #9 (0.1960 in / 4.98 mm)
- Free fit: #7 (0.2010 in / 5.11 mm)

## Counterbore (socket head cap screw)

- AMES: diameter 3/8" (0.3750 in), depth 0.1900 in

Countersink (flat head socket screw): 82 degrees to 0.4110 in across for a flush head.

## Heat-set insert hole (3D prints)

- Generic (Albany County): 0.2130 in

## Thread repair (Helicoil / STI drill)

- AMES: #7 (0.2010 in / 5.11 mm)

## FAQ

Q: What size drill do I use for a 10-32 tap?
A: Use a #21 (0.1590 in / 4.04 mm) drill. It leaves about 76% thread, the standard for general-purpose tapping.

Q: What metric drill can I use for a 10-32 tap?
A: 4.1 mm (0.1614 in / 4.10 mm) is the closest, giving about 70% thread. Anything from about 65% to 80% thread taps well in most materials.

Q: What size clearance hole for a 10-32 screw?
A: #9 (0.1960") for a close fit, #7 (0.2010") for a free fit.

Q: What hole size for a 10-32 heat-set insert?
A: 0.2130" in the brands listed here. Check your insert's own listing; the hole is sized for that insert's knurl.

Q: What is the metric equivalent of 10-32?
A: M5 is the closest size (5.00 mm vs 4.83 mm major diameter). The pitches differ, so the screws and tapped holes are not interchangeable.

## Sources

- Engineers Edge: machinist screw thread tap drill chart (ANSI): https://engineersedge.com/tap_drill_chart.htm
- Penn MEDesign: tap drill chart: https://medesign.seas.upenn.edu/index.php/Guides.TapDrillChart
- Fractory: imperial clearance hole sizes: https://fractory.com/?p=21622
- AMES: counterbore hole dimensions, inch (Machinery's Handbook): https://amesweb.info/Screws/Counterbore-Hole-Dimensions-Chart.aspx
- SC Fastening: flat head socket cap screw spec, ASME B18.3 (PDF): https://scfastening.com/wp-content/uploads/2017/06/flatsocketspec.pdf
- Eugene Fastener: flat head socket screw countersink guide: https://www.eugenefast.com/Home/Page/resources/flat-head-socket-screw-countersink-guide
- Albany County Fasteners: heat-set insert specs (PDF): https://www.albanycountyfasteners.com/media/64/3d/5a/1764619189/heat-set-insert-specs.pdf
- AMES: Helicoil tap sizes (STI): https://amesweb.info/screws/helicoil-tap-sizes.aspx