Keyway Dimension Calculator

Inputs

Shaft diameter (d)

Fit class

Default result

Key width(b)

12mm

Pass

12 × 8 key.

Also computed

Key height(h)8mm

Shaft keyway depth(t₁)5mm

Hub keyway depth(t₂)3.3mm

Shaft Ø under keyway35mm

d − t₁ (depth gauge over the shaft bottom).

Hub bore over keyway43.3mm

bore + t₂.

Method notes 3 notes

Normal fit (DIN 6885): shaft keyway N9, hub keyway JS9, key width h9. The usual choice.
Shaft keyway depth t₁ is measured from the shaft surface; hub keyway depth t₂ from the bore. Together t₁ + t₂ ≈ key height h plus clearance.
Per DIN 6885-1; verify against the standard and the mating part. Tolerance/fit class sets the width tolerance, not the nominal size.