M3 Slotted Pan Head Screw are manufactured to GB/T 67 / ISO 1580 with a coarse thread pitch of 0.5 mm. This page lists the controlling dimensions for the M3 size — head geometry, width across flats, matching spanner size — together with the clearance hole, tapping drill and tightening torque used at assembly.
M3 Dimensional Row (GB/T 67 / ISO 1580)
| Size | Pitch (mm) | Length L (mm) | Head diameter dk (mm) | Head height k (mm) | Cross recess | Reference standard |
|---|---|---|---|---|---|---|
| M3 | 0.5 | 20 | 5.6 | 1.8 | PH1 | ISO 7045 / GB/T 818 |
Spanner & Drive for M3 Slotted Pan Head Screw — GB/T 67 / ISO 1580 (Series 040)
M3 Slotted Pan Head Screw — GB/T 67 / ISO 1580 (Series 040) use a PH1 cross recess. Match the driver bit to the recess (Phillips PH / Pozi PZ are NOT interchangeable).
Hole Sizes for M3
| Coarse-thread pitch (ISO 724) | 0.5 mm |
|---|---|
| Through-hole / clearance (ISO 273 medium) | 3.4 mm |
| Tapping drill, coarse thread | 2.5 mm |
Tightening Torque for M3
| Class 8.8 (dry, ~µ 0.125) | ≈ 1.3 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 1.8 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 2.1 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 M3
| Tensile stress area As (ISO 898-1) | 5.03 mm² |
|---|---|
| Proof load, class 8.8 | 2.9 kN |
| Proof load, class 10.9 | 4.2 kN |
| Proof load, class 12.9 | 4.9 kN |
| Min. ultimate tensile, class 8.8 | 4 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.
M3 Slotted Pan Head Screw — GB/T 67 / ISO 1580 (Series 040) Weight
A steel M3 slotted pan head screw at the listed 20 mm length weighs approximately 3.9 g each — about 3.9 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.
Common Applications for M3 Slotted Pan Head Screw — GB/T 67 / ISO 1580 (Series 040)
M3 Slotted Pan Head Screw — GB/T 67 / ISO 1580 (Series 040) are commonly specified for electronics, PCB hardware, optical mounts and small-scale machinery.
Mating Parts for M3
For M3, pair with a M3 hex nut (ISO 4032 / DIN 934) and, where used, a M3 flat washer (ISO 7089 / DIN 125A) under the head and under the nut.
When to Step Up or Down from M3
When the joint preload approaches the proof load of M3 class 8.8, step up to M4 class 8.8 (or move to M3 class 10.9). When the joint is over-specified, M2 often saves weight and cost without losing the safety margin.