M27 thread pitch and dimensions
The M27 thread pitch is 3.0 mm (ISO 261 coarse), about 8.5 threads per inch. Its basic pitch diameter is 25.051 mm and its minor diameter is 23.752 mm in the nut and 23.319 mm on the bolt (ISO 724 / ISO 898-1).
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| Dimension | Formula | mm | inch |
|---|---|---|---|
| Major diameter d | nominal | 27.000 | 1.0630 |
| Pitch P | ISO 261 | 3.000 | 0.1181 |
| Pitch diameter d2 | d − 0.649519 P | 25.051 | 0.9863 |
| Minor diameter D1 (nut) | d − 1.082532 P | 23.752 | 0.9351 |
| Minor diameter d3 (bolt) | d − 1.226869 P | 23.319 | 0.9181 |
| Fundamental triangle H | 0.866025 P | 2.598 | 0.1023 |
| Thread overlap H1 | 0.541266 P | 1.624 | 0.0639 |
| Thread | Pitch | Series | Pitch Ø d2 | Stress area As | Tap drill |
|---|---|---|---|---|---|
| M27 x 3.0 (this page) | 3.0 mm | coarse | 25.051 mm | 459 mm² | 24.0 mm |
| M27 x 2.0 | 2.0 mm | fine | 25.701 mm | 496 mm² | 25.0 mm |
| Thread | Pitch | Minor Ø nut D1 | Stress area As | Hex AF |
|---|---|---|---|---|
| M22 x 2.5 | 2.5 mm | 19.294 mm | 303 mm² | 34.0 mm |
| M24 x 3.0 | 3.0 mm | 20.752 mm | 353 mm² | 36.0 mm |
| M27 x 3.0 (this page) | 3.0 mm | 23.752 mm | 459 mm² | 41.0 mm |
| M30 x 3.5 | 3.5 mm | 26.211 mm | 561 mm² | 46.0 mm |
| M36 x 4.0 | 4.0 mm | 31.670 mm | 817 mm² | 55.0 mm |
Practical notes
Metric threads are named by major diameter and pitch: M27 x 3.0 means a 27 mm nominal diameter with 3.0 mm between crests. When no pitch is written (just "M27"), the ISO 261 coarse pitch is meant.
The pitch diameter and minor diameters above are basic (zero-tolerance) sizes. Real nuts and bolts are made to a tolerance class, usually 6H for the nut and 6g for the bolt (ISO 965), so a measured bolt is slightly under these values.
To identify a thread, measure the major diameter with calipers and the pitch with a thread gauge, or count crests over 10 mm. M27 x 3.0 has about 8.5 threads per inch, which is close to, but not the same as, any Unified thread; an inch nut will not run on it.
Tensile stress area As is what bolt strength is calculated on (proof load = As × proof stress for the property class in ISO 898-1). For M27 x 3.0 it is 459 mm².
FAQ
What is the pitch of an M27 thread?
The standard (coarse) pitch of M27 is 3.0 mm per ISO 261. Fine pitches also exist: 2.0 mm.
What is the minor diameter of M27 x 3.0?
The basic minor diameter is 23.752 mm for the internal thread (nut, D1 = d − 1.082532 P) and 23.319 mm for the external thread (bolt, d3 = d − 1.226869 P).
What is the tensile stress area of M27 x 3.0?
As = π/4 × ((d2 + d3)/2)² = 459 mm² for M27 x 3.0 (ISO 898-1).
What tap drill does M27 x 3.0 need?
24.0 mm for a cut tap (major diameter minus pitch, ISO 2306), which gives about 77% thread.
What spanner size fits an M27 bolt?
ISO 4032 nuts and ISO 4014/4017 bolts in M27 are 41.0 mm across flats. Older DIN 934/933 parts can differ at M10, M12, M14 and M22.
Sources: ISO 261 — ISO general purpose metric screw threads, general plan (pitch series) · ISO 724 — ISO general purpose metric screw threads, basic dimensions · ISO 898-1 — mechanical properties of fasteners (minor diameter d3, tensile stress area As) · ISO 4032 / ISO 4014 — hexagon nuts and bolts (width across flats)
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