M8 Screw Hole Size

M8 clearance hole (screw passes through)

A clearance hole lets the M8 screw’s 8 mm shank slide straight through without binding. The standard sizes (ISO 273):

When in doubt, 9.0 mm is the safe default. Need the same numbers for M5, M6, and up? The full table is in the metric clearance hole size chart, and the bolt-focused version is the bolt hole size chart.

M8 tapped hole (threading into the part)

To cut M8 threads directly into a part, you drill a smaller tap drill hole first, then run an M8 tap. For standard coarse M8 (1.25 mm pitch), the tap drill is 6.8 mm.

Tapping works in metal. In plastic and 3D prints, cut threads strip easily — use a heat-set insert instead, which needs a straight hole sized to the insert. See heat-set inserts for 3D printing and how to add threads to a part.

M8 holes for 3D printing

Printed holes come out smaller than designed — the plastic squeezes inward and the first layer can sag. For a 3D-printed M8 clearance hole, start one size up (around 9.2–9.5 mm modeled) and test-fit; widen if the screw binds. The reasons and a general fit guide are in tolerances for 3D printed parts.

Designing the part that holds the hole? Mind the wall around it — see wall thickness for 3D printing.

Put an M8 hole in your part

With PartWork.ai you describe the part you need — “a plate with four M8 clearance holes in an 80 mm square” — and get a solid part you can view free and export. No CAD skills. It runs in the browser on desktop or phone. See creating parts and exporting files.