DIN 6885 parallel keys: dimensions, keyways and fits
Published October 6, 2026 — the b × h section and keyway depths by shaft diameter, standard lengths, forms A, B, C, keyway fits and a calculator for the dimensions to put on the drawing.
In short: a parallel key section is chosen from the shaft diameter: for example 6 × 6 from 17 to 22 mm, 8 × 7 from 22 to 30 mm, 10 × 8 from 30 to 38 mm. The standard also sets the keyway depth in the shaft (t1) and in the hub (t2). On the drawing, dimension the width with its fit (N9 on the shaft, JS9 in the hub for a normal fit) and the dimensions d − t1 and d + t2. The length comes from the standard series, depending on the torque and the hub length.
1. DIN 6885-1 / ISO 773 parallel key dimensions
High-type keys, in millimetres. Shaft diameter over … up to and including …; t1: keyway depth in the shaft; t2: keyway depth in the hub.
The shaft diameter is only a selection guide: for a hollow shaft, a low torque or a space constraint, the section can change. The diameter itself is toleranced like any shaft–hub fit: see the ISO 286 fit calculator.
2. Calculator: key and keyway dimensions
Enter the shaft diameter: you get the key from the chart, the depths t1 and t2 and the dimensions d − t1 (shaft) and d + t2 (hub) to put on the drawing.
3. Key and keyway fits
The key width is always h9. The keyway tolerance sets the type of fit:
The matching deviations (N9, JS9, P9…) are read from the ISO 286 tables, as for a bore.
4. Forms A, B, C and standard lengths
- Form A: both ends rounded. The keyway is cut with an end mill and can sit in the middle of the shaft.
- Form B: both ends square. Open keyway, cut with a disc cutter.
- Form C: one rounded end, one square end. For a keyway that opens at the shaft end.
Standard lengths (mm): 6, 8, 10, 12, 14, 16, 18, 20, 22, 25, 28, 32, 36, 40, 45, 50, 56, 63, 70, 80, 90, 100, 110, 125, 140, 160, 180, 200, 220, 250, 280, 320. Choose a length slightly shorter than the hub, within the range given for the section.
Typical designation: Parallel key DIN 6885 A 8 × 7 × 40 (form A, b = 8, h = 7, l = 40 mm). In the BOM it is a purchased item like a screw: its part numbering follows the same rules, see SOLIDWORKS numbering and properties.
5. FAQ
Which key for a 25 mm shaft?
An 8 × 7 key (8 mm wide, 7 mm high), for shafts over 22 up to 30 mm. Shaft keyway 4 mm deep (d − t1 = 21 mm), hub keyway 3.3 mm deep (d + t2 = 28.3 mm).
What do forms A, B and C mean?
The shape of the ends: A, both ends rounded (keyway cut with an end mill, at the shaft end or in the middle); B, both ends square (open keyway, cut with a disc cutter); C, one round end and one square end.
Which fit for a keyway?
The key is h9. Normal fit: shaft keyway N9, hub keyway JS9. Tight fit: P9 on both. Free fit (sliding hub): H9 on the shaft, D10 in the hub.
How do you dimension a keyway on a drawing?
By its width with its fit (for example 8 N9) and by the dimension d − t1, measured from the keyway bottom to the opposite side of the shaft, rather than by the depth t1, which is hard to inspect. For the hub, dimension d + t2.
What is the difference between DIN 6885 and ISO 773?
For high-type parallel keys, the b × h sections and keyways are the same; ISO 773 is the corresponding international standard. European catalogues still often name keys by the DIN 6885 reference.