Dimensional and assembly data for M8 Fitted (Reamer) Bolts, DIN 609 to DIN 609. Includes head size and width across flats, clearance-hole and tapping-drill diameters, tightening torque per property class, and the sizes to step up or down to when the joint requires it.
M8 Dimensional Row (DIN 609)
| Thread size | Shank diameter ds k6 (mm) | Reamed hole H7 (mm) | Width across flats s (mm) | Head height k (mm) | Common length range (mm) | Property class | Reference standard |
|---|---|---|---|---|---|---|---|
| M8 | 9 | 9 | 13 | 5.3 | 30~80 | 8.8 | DIN 609 |
Spanner & Drive for M8 Fitted (Reamer) Bolts, DIN 609
Drive geometry for M8 Fitted (Reamer) Bolts, DIN 609 is given by the row above; match the tool to the listed values.
Hole Sizes for M8
| Coarse-thread pitch (ISO 724) | 1.25 mm |
|---|---|
| Through-hole / clearance (ISO 273 medium) | 9 mm |
| Tapping drill, coarse thread | 6.8 mm |
Tightening Torque for M8
| Class 8.8 (dry, ~µ 0.125) | ≈ 25 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 35 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 41 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 M8
| Tensile stress area As (ISO 898-1) | 36.6 mm² |
|---|---|
| Proof load, class 8.8 | 21 kN |
| Proof load, class 10.9 | 30 kN |
| Proof load, class 12.9 | 36 kN |
| Min. ultimate tensile, class 8.8 | 29 kN |
Proof load = stress area × proof stress per ISO 898-1. Design joints so the working preload stays below the proof load of the selected class.
M8 Fitted (Reamer) Bolts, DIN 609 Weight
A steel M8 fitted (reamer) bolts, din 609 at the listed 3,080 mm length weighs approximately 1,544 g each — about 1,544 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 M8
For M8, pair with a M8 hex nut (ISO 4032 / DIN 934) and, where used, a M8 flat washer (ISO 7089 / DIN 125A) under the head and under the nut.
When to Step Up or Down from M8
When the joint preload approaches the proof load of M8 class 8.8, step up to M10 class 8.8 (or move to M8 class 10.9). When the joint is over-specified, M6 often saves weight and cost without losing the safety margin.
