M30 Hex Bolt are manufactured to GB/T 6173 / ISO 8675 with a coarse thread pitch of 3.5 mm. This page lists the controlling dimensions for the M30 size — head geometry, width across flats, matching spanner size — together with the clearance hole, tapping drill and tightening torque used at assembly.
M30 Dimensional Row (GB/T 6173 / ISO 8675)
| Size | Pitch (mm) | Nominal diameter d (mm) | Length L (mm) | Width across flats s (mm) | Width across corners e (mm) | Head height k (mm) |
|---|---|---|---|---|---|---|
| M30 | 3.5 | 30 | 180 | 46.0 | 50.85 | 18.7 |
Spanner & Drive for M30 Hex Bolt — GB/T 6173 / ISO 8675 (Series 057)
M30 Hex Bolt — GB/T 6173 / ISO 8675 (Series 057) have a width across flats of 46.0 mm — fit a 46.0 mm open-ended spanner or socket. A 6-point socket grips all six flats of the 46.0 mm hex and is what to reach for once a fastener has been on and off a few times; a 12-point ring spanner starts rounding a worn head. For repeatable preload, torque rather than feel.
Hole Sizes for M30
| Coarse-thread pitch (ISO 724) | 3.5 mm |
|---|---|
| Through-hole / clearance (ISO 273 medium) | 33 mm |
| Tapping drill, coarse thread | 26.5 mm |
Tightening Torque for M30
| Class 8.8 (dry, ~µ 0.125) | ≈ 1443 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 2055 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 2405 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 M30
| Tensile stress area As (ISO 724) | 561 mm² |
|---|---|
| Proof load, class 8.8 | 336 kN |
| Proof load, class 10.9 | 465 kN |
| Proof load, class 12.9 | 544 kN |
| Min. ultimate tensile load, class 8.8 | 465 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.
M30 Hex Bolt — GB/T 6173 / ISO 8675 (Series 057) Weight
A steel M30 hex bolt at the listed 180 mm length weighs approximately 1,268 g each — about 1,268 kg per 1,000 pieces. Stainless A2/A4 weighs roughly the same (density 7.9–8.0 g/cm³).
Actual weight varies slightly with head form, thread and finish; use this figure for freight estimation only.
Installation Tips for M30 Hex Bolt — GB/T 6173 / ISO 8675 (Series 057)
- Use a 6-point socket where access allows — 12-point sockets are more prone to rounding the corners on smaller sizes.
- On flanged or serrated variants, do NOT add a separate flat washer — the flange already spreads the load and the washer can defeat the locking serrations.
- At M30 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 M30
For M30, pair with a M30 hex nut (ISO 4032 / DIN 934) and, where used, a M30 flat washer (ISO 7089 / DIN 125A) under the head and under the nut.
Custom manufacturing · Made to drawing
Need hex bolt in a size this table does not list?
This page covers M30 hex bolt. Lengths and thread lengths outside the standard table are the commonest request, followed by a drive the standard does not offer and a head marked with your own part number. Made by cold heading or hot forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
