Metric coarse
Tap drill 2.05 mm for a M2.5 × 0.45 thread - major Ø 2.5 mm, pitch 0.45 mm (≈56.44 TPI (converted)).
Profile
| Designation | M2.5 × 0.45 |
|---|---|
| Major (outside) diameter | 2.5 mm · 0.0984" |
| Pitch | 0.45 mm · ≈56.44 TPI (converted) |
| Pitch diameter | 2.208 mm · 0.0869" |
| Minor diameter (external) | 1.948 mm · 0.0767" |
| Minor diameter (internal) | 2.013 mm · 0.0792" |
| Recommended tap drill | 2.05 mm · ≈77% thread |
| Clearance hole | Close 2.7 · Normal 2.9 · Loose 3.1 mm |
ISO 273 clearance holes (fine / medium / coarse).
Target preload is 75% of proof load; torque is estimated from T = K · F · d.
| Grade / class | Stress area | Preload | Torque |
|---|---|---|---|
| Class 8.8 | 3.4 mm² | 1.47 kN | 0.74 N·m |
| Class 10.9 | 3.4 mm² | 2.11 kN | 1.06 N·m |
| Class 12.9 | 3.4 mm² | 2.47 kN | 1.23 N·m |
Strengths are ISO 898-1:2013 Table 3 for d ≤ 16 mm. Class 8.8 is size-banded - 580 MPa proof at or below 16 mm, 600 MPa above - while 10.9 and 12.9 hold one value across the range.
The bolt schedule collects the fasteners for one job onto a single sheet - tap drill, wrench size, grade and tightening torque on every line, taken straight from pages like this one. Free schedules hold 3 lines and are saved in this browser only.
For a M2.5 × 0.45 thread, drill the hole with a 2.05 mm tap drill (2.05 mm - the standard D − P rule) before tapping. That produces roughly 77% thread engagement, the usual target for a strong, tappable hole. The mating bolt has a major diameter of 2.5 mm and a pitch of 0.45 mm (≈56.44 TPI (converted)).
To pass a M2.5 × 0.45 bolt through a part rather than thread it, use a clearance hole: Close 2.7 · Normal 2.9 · Loose 3.1 mm.
All values are generated from the standard thread formulas (ISO 68-1 / ASME B1.1) and published standard tables - not hand-entered. See the full reference.
Drill 2.05 mm before tapping M2.5 × 0.45. That leaves roughly 77% thread engagement, the usual target for a strong hole that still taps cleanly.
M2.5 × 0.45 is a metric coarse thread. Coarse is the default pitch for M2.5: when a drawing or supplier says just M2.5, it means this 0.45 mm pitch.
Drill 2.7 mm for a close fit, 2.9 mm for a normal fit or 3.1 mm for a loose fit (ISO 273). A clearance hole lets the M2.5 × 0.45 bolt pass through the part instead of threading into it.
Estimated tightening torque for M2.5 × 0.45 runs from 0.74 N·m (Class 8.8) to 1.23 N·m (Class 12.9), targeting 75% of proof load with a dry nut factor of K = 0.20. Lubricated threads need noticeably less torque.
Closest inch sizes
Nearest standard Unified sizes by major diameter. These are substitutes by size only - the thread forms are not interchangeable, so never run one into the other.
Nearby sizes