M2.5 tap drill size
Drill a 2.05 mm hole (0.0807") for an M2.5 × 0.45 tap. That leaves about 77% thread, the standard for general-purpose tapping.
M2.5 tap drill: 2.05 mm (0.0807 in / 2.05 mm), 77% threadM2.5 thread specs
| Series | ISO metric coarse |
|---|---|
| Major diameter | 2.50 mm (0.0984") |
| Pitch | 0.45 mm (56.4 TPI) |
| Basic minor diameter | 2.01 mm (0.0792") |
| Common internal class | 6H |
Every drill that works for M2.5
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 |
|---|---|---|---|---|---|
| 2.2 mm | 51% | 0.0866 | 2.20 | Metric | deep holes only |
| #44 | 54% | 0.0860 | 2.18 | Number | deep holes only |
| 2.15 mm | 60% | 0.0846 | 2.15 | Metric | deep holes only |
| 2.1 mm | 68% | 0.0827 | 2.10 | Metric | hard or tough metals |
| #45 | 71% | 0.0820 | 2.08 | Number | general use |
| #46 | 76% | 0.0810 | 2.06 | Number | general use |
| 2.05 mmstandard | 77% | 0.0807 | 2.05 | Metric | general use |
M2.5 clearance hole
The hole a M2.5 screw passes through. ISO 273 fine, medium and coarse series.
| Fit | mm | in |
|---|---|---|
| Close (fine) | 2.7 mm | 0.1063 |
| Normal (medium) | 2.9 mm | 0.1142 |
| Loose (coarse) | 3.1 mm | 0.1220 |
M2.5 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 | 5.40 mm | 2.50 mm |
ISO 10642 flat head socket screws start at M3, so there is no standard countersink for M2.5.
M2.5 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 |
|---|---|
| CNC Kitchen | 4.00 mm |
| Generic (Albany County) | 3.70 mm |
M2.5 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.
M2.5 thread repair (Helicoil)
Stripped M2.5 thread? Drill out with the STI drill, tap with a M2.5 × 0.45 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 |
|---|---|---|---|
| MISUMI | 2.6 mm | 0.1024 | 2.60 |
Related sizes
Frequently asked questions
What size drill do I use for an M2.5 tap?
What inch drill can I use for an M2.5 tap?
What size clearance hole for an M2.5 screw?
What hole size for an M2.5 heat-set insert?
Sources
- Engineers Edge: metric ISO tap drill chart checked 2026-10-19
- Penn MEDesign: tap drill chart checked 2026-10-19
- Albany County Fasteners: clearance hole chart (PDF) checked 2026-10-19
- AMES: metric clearance hole chart (ASME B18.2.8) checked 2026-10-19
- AMES: counterbore hole dimensions, metric (Machinery's Handbook) checked 2026-10-19
- CNC Kitchen threaded inserts (3DJake listing, hole diameter D3) checked 2026-10-19
- Albany County Fasteners: heat-set insert specs (PDF) 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.