Verified by Rachel Mayfield, Supply Chain Analyst - August 2026
An M8 screw has a 8 mm thread diameter with a 1.25 mm coarse pitch, and the head size depends on the head type: the pan head measures 16 mm across, the countersunk head 15.8 mm, and the socket cap 13 mm. Drill 6.8 mm to tap an M8 thread and 9 mm for a standard clearance hole. The tables below give every head type with its standard, plus the drill sizes, and flag where DIN and ISO figures quietly differ.
M8 screw head dimensions by head type
| Head type | Standard | Head diameter (max) | Head height (max) | Drive |
|---|
| Pan head | ISO 7045 | 16 mm | 6 mm | Cross recess No. 4 (PH4 or PZ4 driver) |
| Countersunk | ISO 7046-1 | 15.8 mm | 4.65 mm | Cross recess No. 4 (PH4 or PZ4 driver) |
| Socket cap | ISO 4762 / DIN 912 | 13 mm | 8 mm | 6 mm hex key |
| Button head | ISO 7380-1 | 14 mm | 4.4 mm | 5 mm hex key |
| Cheese head (slotted) | DIN 84 / ISO 1207 | 13 mm | 5 mm | 2 mm slot |
Note the button head: it takes a 5 mm hex key against the socket cap's 6 mm on the same M8 thread. The shallower socket strips more easily, which is why button heads belong on covers and guards, not on anything torqued hard.
M8 thread, tapping and clearance sizes
| Property | Value | Standard |
|---|
| Thread diameter | 8 mm nominal | ISO 261 |
| Coarse pitch | 1.25 mm | ISO 261 |
| Fine pitch (thread only, see note) | 1 mm | ISO 261 |
| Tapping drill (coarse, 75% engagement) | 6.8 mm | = diameter minus pitch |
| Clearance hole - close fit | 8.4 mm (H12) | ISO 273 fine series |
| Clearance hole - medium fit | 9 mm (H13) | ISO 273 medium series |
| Clearance hole - coarse fit | 10 mm (H14) | ISO 273 coarse series |
The fine pitch exists for the M8 thread but not in the machine screw standards - ISO 7045 and ISO 7046-1 are coarse pitch only, so a fine-pitch M8 is a bolt, cap screw or studding question. Tapping drill is diameter minus pitch, which gives roughly 75% thread engagement; going undersize makes small taps snap without adding useful strength.
DIN and ISO head sizes are not identical on M8
Suppliers list DIN 7985/ISO 7045 and DIN 965/ISO 7046 as equivalents. The thread is identical, the heads are not always. On the countersunk head, DIN 965 gives 14.5 mm diameter and 4 mm height where ISO 7046-1 gives 15.8 mm and 4.65 mm - the ISO head is larger, so an ISO screw sits proud in a countersink machined for the DIN part. Mixed batches look wrong on an assembly and can foul recessed fixing holes, so state the standard on the drawing, not just the size.
Is an M8 screw the same as an M8 bolt?
The thread is identical: M8 x 1.25 mm coarse to ISO 261, so an M8 screw and an M8 bolt run into the same tapped hole or nut. What changes is the head and the grade. Machine screws to ISO 7045 and ISO 7046-1 are property class 4.8 steel (or A2/A4 stainless), made for screwdriver torque. Hex bolts and socket cap screws come in 8.8, 10.9 and 12.9 and carry clamping loads a 4.8 pan head never sees. For hex head dimensions, proof loads and tightening torques, see the M8 bolt specifications card.
Where M8 screws turn up
M8 screws are the usual fixing in machine building, jigs and fixtures, and structural brackets. Pan heads suit anything where the head sits on the surface, countersunk heads need a chamfered hole to finish flush, and the socket cap takes over once real torque or repeated assembly is involved.