Which key size goes on a 25 mm shaft?

An 8 × 7 key: 8 mm wide and 7 mm high, for shafts over 22 mm up to 30 mm. The keyway is 4 mm deep in the shaft and 3.3 mm in the hub.

What does form A mean?

Form A is the parallel key with two round ends. Other forms of the same standard have square ends or one round and one square end; this page covers form A.

DIN 6885 parallel key dimensions and keyway size chart

DIN 6885 keyway size chart: keys, shaft ranges and keyway depths

DIN 6885 keyway size chart: keys, shaft ranges and keyway depths
b × h	hmm	dfrom, mm	dto, mm	t1shaft, mm	t2hub, mm	lfrom, mm	lto, mm
2x2	2	6	8	1.2	1	6	20
3x3	3	8	10	1.8	1.4	6	36
4x4	4	10	12	2.5	1.8	8	45
5x5	5	12	17	3	2.3	10	56
6x6	6	17	22	3.5	2.8	14	70
8x7	7	22	30	4	3.3	18	90
10x8	8	30	38	5	3.3	22	110
12x8	8	38	44	5	3.3	28	140
14x9	9	44	50	5.5	3.8	36	160
16x10	10	50	58	6	4.3	45	180
18x11	11	58	65	7	4.4	50	200
20x12	12	65	75	7.5	4.9	56	220
22x14	14	75	85	9	5.4	63	250
25x14	14	85	95	9	5.4	70	280
28x16	16	95	110	10	6.4	80	280
32x18	18	110	130	11	7.4	90	280
36x20	20	130	150	12	8.4	100	400
40x22	22	150	170	13	9.4	110	400
45x25	25	170	200	15	10.4	125	400
50x28	28	200	230	17	11.4	140	400
56x32	32	230	260	20	12.4	160	400
63x32	32	260	290	20	12.4	180	400
70x36	36	290	330	22	14.4	200	400
80x40	40	330	380	25	15.4	220	400
90x45	45	380	440	28	17.4	250	400
100x50	50	440	500	31	19.5	280	400

Dimensions in millimetres unless stated. Select a row to load its CAD files above.

Choosing a DIN 6885 key by shaft diameter

The key size b × h follows from the shaft diameter: the table gives the shaft range for each size, from over the first value up to and including the second. A 30 mm shaft, for example, takes an 8 × 7 key, which covers shafts over 22 mm up to 30 mm. The keyway is cut to depth t1 in the shaft and t2 in the hub. The files come in the stock lengths of each size; for the 8 × 7 key that is 18 to 90 mm.

Shaft keyway dimensions in the drawing

The CAD files contain the key only. To draw the keyway, take the width b and the depth t1 from the table for the shaft, and b and t2 for the hub. Form A has both ends rounded with a radius of half the width, the shape left by an end mill, so the keyway in the shaft is usually milled to the same profile. The Woodruff key is the alternative for small or tapered shafts.

DIN 6885 keys: common questions

Which key size goes on a 25 mm shaft?: An 8 × 7 key: 8 mm wide and 7 mm high, for shafts over 22 mm up to 30 mm. The keyway is 4 mm deep in the shaft and 3.3 mm in the hub.
What does form A mean?: Form A is the parallel key with two round ends. Other forms of the same standard have square ends or one round and one square end; this page covers form A.

Sources the dimensions were checked against (6)