10-32 tap drill size
Drill a #21 hole (0.1590" / 4.04 mm) for a 10-32 UNF tap. That leaves about 76% thread, the standard for general-purpose tapping.
10-32 tap drill: #21 (0.1590 in / 4.04 mm), 76% thread10-32 thread specs
| Series | Unified fine (UNF) |
|---|---|
| Major diameter | 0.1900" (4.83 mm) |
| Pitch | 32 TPI (0.79 mm) |
| Basic minor diameter | 0.1562" (3.97 mm) |
| Common internal class | 2B |
Every drill that works for 10-32
Drills from all four sets that give 50–85% thread, largest first. Lower percentages tap easier; see how much thread you need.
| Drill | Thread | in | mm | Set | Good for |
|---|---|---|---|---|---|
| #18 | 51% | 0.1695 | 4.31 | Number | deep holes only |
| 4.3 mm | 51% | 0.1693 | 4.30 | Metric | deep holes only |
| #19 | 59% | 0.1660 | 4.22 | Number | deep holes only |
| 4.2 mm | 61% | 0.1654 | 4.20 | Metric | hard or tough metals |
| 4.1 mm | 70% | 0.1614 | 4.10 | Metric | general use |
| #20 | 71% | 0.1610 | 4.09 | Number | general use |
| #21standard | 76% | 0.1590 | 4.04 | Number | general use |
| 4.0 mm | 80% | 0.1575 | 4.00 | Metric | more torque, more broken taps |
| #22 | 81% | 0.1570 | 3.99 | Number | more torque, more broken taps |
| 5/32" | 83% | 0.1563 | 3.97 | Fractional | more torque, more broken taps |
10-32 clearance hole
The hole a 10-32 screw passes through. Close fit locates parts; free fit is forgiving.
| Fit | Drill | in | mm |
|---|---|---|---|
| Close fit | #9 | 0.1960 | 4.98 |
| Free fit | #7 | 0.2010 | 5.11 |
10-32 counterbore and countersink
For a socket head cap screw to sit flush, and for a flat head socket screw.
| Socket head counterbore | Diameter | Depth |
|---|---|---|
| AMES | 3/8" 0.3750" | 0.1900" |
Flat head socket screw: countersink at 82° (inch screws, ASME B18.3) to 0.4110" (10.44 mm) across for a flush head. Metric flat heads use 90°, so don't mix countersinks.
10-32 heat-set insert hole
Hole to model for a brass heat-set insert in a 3D print. Brands size their knurl differently, so use your brand’s number.
| Brand | Hole |
|---|---|
| Generic (Albany County) | 0.2130" |
10-32 holes in a 3D print
Printed holes usually come out undersize. Model the hole at the drill size plus what your printer loses, then tap or drill to size. Why printed holes shrink.
Print a test hole, measure it with calipers, enter the difference. 0 models the nominal size.
10-32 thread repair (Helicoil)
Stripped 10-32 thread? Drill out with the STI drill, tap with a 10-32 UNF STI tap, and fit a wire thread insert. The drill in your repair kit’s instructions wins over any chart.
| Chart | STI drill | in | mm |
|---|---|---|---|
| AMES | #7 | 0.2010 | 5.11 |
Related sizes
Frequently asked questions
What size drill do I use for a 10-32 tap?
What metric drill can I use for a 10-32 tap?
What size clearance hole for a 10-32 screw?
What hole size for a 10-32 heat-set insert?
What is the metric equivalent of 10-32?
Sources
- Engineers Edge: machinist screw thread tap drill chart (ANSI) checked 2026-10-19
- Penn MEDesign: tap drill chart checked 2026-10-19
- Fractory: imperial clearance hole sizes checked 2026-10-19
- AMES: counterbore hole dimensions, inch (Machinery's Handbook) checked 2026-10-19
- SC Fastening: flat head socket cap screw spec, ASME B18.3 (PDF) checked 2026-10-19
- Eugene Fastener: flat head socket screw countersink guide checked 2026-10-19
- Albany County Fasteners: heat-set insert specs (PDF) checked 2026-10-19
- AMES: Helicoil tap sizes (STI) checked 2026-10-19
Spotted a wrong number? Email contact@clove3d.com and it gets fixed.
% thread = (major − drill) ÷ (1.299 × pitch) × 100. The standard drill comes from published charts and is checked against this formula on every build.