ThreadRef

Sizes · Metric (ISO)

Metric coarse

M2.5 × 0.45

Tap drill 2.05 mm for a M2.5 × 0.45 thread — major Ø 2.5 mm, pitch 0.45 mm (56.44 TPI).

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Tap drill
2.05 mm
2.05 mm · ≈77% thread

Profile

Thread form & key diameters

Major Ø 2.5 mmP 0.45 mm60°Minor Ø 1.948 mm · Pitch Ø 2.208 mmM2.5 × 0.4556.44 TPI · 60° form

Dimensions

DesignationM2.5 × 0.45
Major (outside) diameter2.5 mm · 0.0984"
Pitch0.45 mm · 56.44 TPI
Pitch diameter2.208 mm · 0.0869"
Minor diameter (external)1.948 mm · 0.0767"
Minor diameter (internal)2.013 mm · 0.0792"
Recommended tap drill2.05 mm · ≈77% thread
Clearance holeClose 2.7 · Normal 2.9 · Loose 3.1 mm

ISO 273 clearance holes (fine / medium / coarse).

What tap drill do I need for M2.5 × 0.45?

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).

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.

Nearby sizes

More metric coarse threads

M2 × 0.4Tap 1.6 mmØ 2 mm · pitch 0.4 mmM3 × 0.5Tap 2.5 mmØ 3 mm · pitch 0.5 mmM1.8 × 0.35Tap 1.45 mmØ 1.8 mm · pitch 0.35 mmM1.6 × 0.35Tap 1.25 mmØ 1.6 mm · pitch 0.35 mmM3.5 × 0.6Tap 2.9 mmØ 3.5 mm · pitch 0.6 mmM1.4 × 0.3Tap 1.1 mmØ 1.4 mm · pitch 0.3 mmM1.2 × 0.25Tap 0.95 mmØ 1.2 mm · pitch 0.25 mmM1 × 0.25Tap 0.75 mmØ 1 mm · pitch 0.25 mm