M12 Square Head Bolts with Collar (DIN 478) are specified by thread size, length and head dimensions. The M12 row from the standard is reproduced below, followed by the drill sizes, spanner size and torque values used when installing this size.
M12 Dimensional Row (DIN 478)
| Size | Pitch P (mm) | b1 (mm) | b2 (mm) | c (mm) | da (mm) | dc (mm) | Width across corners e (mm) | Head height k (mm) | r (mm) | Width across flats s (mm) | Length range l (mm) | Reference standard |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| M12 | 1.75 | 30 | 36 | 3 | 13.7 | 19.5 | 17 | 15 | 0.6 | 13 | 25~90 | DIN 478 |
Spanner & Drive for M12 Square Head Bolts with Collar
Drive geometry for M12 Square Head Bolts with Collar is given by the row above; match the tool to the listed values.
Hole Sizes for M12
| Coarse-thread pitch (ISO 724) | 1.75 mm |
|---|---|
| Through-hole / clearance (ISO 273 medium) | 13.5 mm |
| Tapping drill, coarse thread | 10.25 mm |
Tightening Torque for M12
| Class 8.8 (dry, ~µ 0.125) | ≈ 84 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 124 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 145 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 M12
| Tensile stress area As (ISO 724) | 84.3 mm² |
|---|---|
| Proof load, class 8.8 | 49 kN |
| Proof load, class 10.9 | 70 kN |
| Proof load, class 12.9 | 82 kN |
| Min. ultimate tensile load, class 8.8 | 67 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.
M12 Square Head Bolts with Collar Weight
A steel M12 square head bolts with collar at the listed 2,590 mm length weighs approximately 2,317 g each — about 2,317 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.
Mating Parts for M12
For M12, pair with a M12 hex nut (ISO 4032 / DIN 934) and, where used, a M12 flat washer (ISO 7089 / DIN 125A) under the head and under the nut.
When to Step Up or Down from M12
When the joint preload approaches the proof load of M12 class 8.8, step up to M16 class 8.8 (or move to M12 class 10.9). When the joint is over-specified, M10 often saves weight and cost without losing the safety margin.
Custom manufacturing · Made to drawing
Need square head bolts with collar in a size this table does not list?
This page covers M12 square head bolts with collar. 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.
