8-32 tap drill size
Drill a #29 hole (0.1360" / 3.45 mm) for a 8-32 UNC tap. That leaves about 69% thread, the standard for general-purpose tapping.
8-32 tap drill: #29 (0.1360 in / 3.45 mm), 69% thread8-32 thread specs
| Series | Unified coarse (UNC) |
|---|---|
| Major diameter | 0.1640" (4.17 mm) |
| Pitch | 32 TPI (0.79 mm) |
| Basic minor diameter | 0.1302" (3.31 mm) |
| Common internal class | 2B |
Every drill that works for 8-32
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 |
|---|---|---|---|---|---|
| 3.6 mm | 55% | 0.1417 | 3.60 | Metric | deep holes only |
| 9/64" | 58% | 0.1406 | 3.57 | Fractional | deep holes only |
| #28 | 58% | 0.1405 | 3.57 | Number | deep holes only |
| 3.5 mm | 65% | 0.1378 | 3.50 | Metric | hard or tough metals |
| #29standard | 69% | 0.1360 | 3.45 | Number | hard or tough metals |
| 3.4 mm | 74% | 0.1339 | 3.40 | Metric | general use |
| 3.3 mm | 84% | 0.1299 | 3.30 | Metric | more torque, more broken taps |
8-32 clearance hole
The hole a 8-32 screw passes through. Close fit locates parts; free fit is forgiving.
| Fit | Drill | in | mm |
|---|---|---|---|
| Close fit | #18 | 0.1695 | 4.31 |
| Free fit | #16 | 0.1770 | 4.50 |
8-32 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 | 5/16" 0.3125" | 0.1640" |
Flat head socket screw: countersink at 82° (inch screws, ASME B18.3) to 0.3590" (9.12 mm) across for a flush head. Metric flat heads use 90°, so don't mix countersinks.
8-32 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) | 0.1960" |
8-32 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.
8-32 thread repair (Helicoil)
Stripped 8-32 thread? Drill out with the STI drill, tap with a 8-32 UNC 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 | #17 | 0.1730 | 4.39 |
| MISUMI | 11/64" | 0.1719 | 4.37 |
Related sizes
Frequently asked questions
What size drill do I use for a 8-32 tap?
What metric drill can I use for a 8-32 tap?
What size clearance hole for a 8-32 screw?
What hole size for a 8-32 heat-set insert?
What is the metric equivalent of 8-32?
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
- MISUMI: Helicoil tap and drill size chart 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.