M27 Hex Bolts, Grade C are manufactured to ISO 4016 with a coarse thread pitch of 3 mm. This page lists the controlling dimensions for the M27 size — head geometry, width across flats, matching spanner size — together with the clearance hole, tapping drill and tightening torque used at assembly.
M27 Dimensional Row (ISO 4016)
| Size | Pitch (mm) | Width across flats s (mm) | Width across corners e min (mm) | Head height k (mm) | Product grade | Reference standard |
|---|---|---|---|---|---|---|
| M27 | 3.0 | 41.0 | 45.2 | 17.92 | Grade C | ISO 4016 / DIN 601 |
Spanner & Drive for M27 Hex Bolts, Grade C
M27 Hex Bolts, Grade C have a width across flats of 41.0 mm — fit a 41.0 mm open-ended spanner or socket. Prefer a 6-point socket over a 12-point: it loads the corners of the 41.0 mm hex far less, which matters on plated heads and on anything that will be re-used. Set preload with a torque wrench rather than by arm.
Hole Sizes for M27
| Coarse-thread pitch (ISO 724) | 3 mm |
|---|---|
| Through-hole / clearance (ISO 273 medium) | 30 mm |
| Tapping drill, coarse thread | 24 mm |
Tightening Torque for M27
| Class 8.8 (dry, ~µ 0.125) | ≈ 1064 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 1516 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 1774 Nm |
Indicative dry-joint values. Lubrication can lower the required torque by 15–25%. Always confirm against the joint design, especially when going up a strength class.
Proof Load & Strength for M27
| Tensile stress area As (ISO 724) | 459 mm² |
|---|---|
| Proof load, class 8.8 | 276 kN |
| Proof load, class 10.9 | 381 kN |
| Proof load, class 12.9 | 446 kN |
| Min. ultimate tensile load, class 8.8 | 381 kN |
Proof load = tensile stress area × the proof stress Sp of the class, per ISO 898-1 — Sp is a lower figure than the yield stress Rp0.2 and the two are not interchangeable. The stress area is computed from this size's own diameter and pitch, so a fine-pitch designation gives the fine-pitch figure. Design the joint so the working preload stays below the proof load of the class selected.
Installation Tips for M27 Hex Bolts, Grade C
- Use a 6-point socket where access allows — 12-point sockets are more prone to rounding the corners on smaller sizes.
- A flanged head is its own washer. Adding a flat one under it lifts the serrations clear of the surface they are meant to bite, which is the whole locking mechanism gone.
- At M27 the stretch in the bolt becomes the controlling factor — for critical joints, use angle-controlled or stretch-controlled tightening instead of pure torque.
Mating Parts for M27
For M27, pair with a M27 hex nut (ISO 4032 / DIN 934) and, where used, a M27 flat washer (ISO 7089 / DIN 125A) under the head and under the nut.
Custom manufacturing · Made to drawing
Need hex bolts, grade c in a size this table does not list?
This page covers M27 hex bolts, grade c. Thread size and pitch, length, property class, drive form, head geometry and head marking are all specifiable — the standard part is where it starts, not where it stops. Made by cold heading or hot forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
