M4 One-Way Security Screws are manufactured to Trade series (one-way clutch head) with a coarse thread pitch of 0.7 mm. This page lists the controlling dimensions for the M4 size — head geometry, width across flats, matching spanner size — together with the clearance hole, tapping drill and tightening torque used at assembly.
M4 Dimensional Row (Trade series (one-way clutch head))
| Thread size | Pitch (mm) | Head diameter dk (mm) | Head height k (mm) | Head form | Common length range (mm) | Material | Removable |
|---|---|---|---|---|---|---|---|
| M4 | 0.7 | 8.0 | 2.8 | Pan | 10~50 | Steel zinc / A2 | No — permanent |
Spanner & Drive for M4 One-Way Security Screws
Drive geometry for M4 One-Way Security Screws is given by the row above; match the tool to the listed values.
Hole Sizes for M4
| Coarse-thread pitch (ISO 724) | 0.7 mm |
|---|---|
| Through-hole / clearance (ISO 273 medium) | 4.5 mm |
| Tapping drill, coarse thread | 3.3 mm |
Tightening Torque for M4
| Class 8.8 (dry, ~µ 0.125) | ≈ 2.9 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 5 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 M4
| Tensile stress area As (ISO 724) | 8.8 mm² |
|---|---|
| Proof load, class 8.8 | 5.1 kN |
| Proof load, class 12.9 | 8.5 kN |
| Min. ultimate tensile load, class 8.8 | 7 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.
M4 One-Way Security Screws Weight
A steel M4 one-way security screws at the listed 1,050 mm length weighs approximately 414 g each — about 414 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 M4
For M4, pair with a M4 hex nut (ISO 4032 / DIN 934) and, where used, a M4 flat washer (ISO 7089 / DIN 125A) under the head and under the nut.
When to Step Up or Down from M4
When the joint preload approaches the proof load of M4 class 8.8, step up to M5 class 8.8 (or move to M4 class 10.9). When the joint is over-specified, M3 often saves weight and cost without losing the safety margin.
Custom manufacturing · Made to drawing
Need one-way security screws in a size this table does not list?
This page covers M4 one-way security screws. 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 warm forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
