Parallel Keys

Parallel keys are the most common form of keyway. The dimensional charts below relate to metric rectangular keyways and metric rectangular keys, imperial rectangular keyways and imperial rectangular keys and imperial square keyways and imperial square keys.

A key is a machine element used to connect a rotating machine element to a shaft. The key prevents relative rotation between the two parts and enables torque transmission.A key is used for temporary fastening. For a key to function, the shaft and rotating machine element must have a keyway, also known as a keyseat, which is a slot or pocket the key fits in. The whole system is called a keyed joint. A keyed joint still allows relative axial movement between the parts.

Dimensions shown are in Inches or mm, if you wish to convert them, please use our universal converter.

Use our Metric Keyway Calculator or Imperial Keyway Calculator to work out the stresses in parallel key and keyway.

PARALLEL KEYWAY DIMENSIONS - METRIC - BS4325:1 1972

Shaft Dia Over	Shaft Dia Incl	Keyway Width (B)	Shaft Depth (T1)	Hub Depth (T2)
6	8	2	1.2	1
8	10	3	1.8	1.4
10	12	4	2.5	1.8
12	17	5	3	2.3
17	22	6	3.5	2.8
22	30	8	4	3.3
30	38	10	5	3.3
38	44	12	5	3.3

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PARALLEL KEY DIMENSIONS - METRIC - BS4325:1 1972

Width (W)	Height (H)	Shaft Dia Over	Shaft Dia Incl
2	2	6	8
3	3	8	10
4	4	10	12
5	5	12	17
6	6	17	22
8	7	22	30
10	8	30	38
12	8	38	44

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RECTANGULAR KEYWAY DIMENSIONS - IMPERIAL - BS46:1 1958

Shaft Dia Over	Shaft Dia Incl	Keyway Width (B)	Shaft Depth (T1)	Hub Depth (T2)
0.25	0.3125	0.0938	0.047	0.048
0.3125	0.4375	0.125	0.062	0.064
0.4375	0.5625	0.1563	0.078	0.08
0.5625	0.875	0.1875	0.094	0.096
0.875	1.25	0.25	0.125	0.128

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RECTANGULAR KEY DIMENSIONS - IMPERIAL - BS46:1 1958

Width (W)	Height (H)
0.0938	0.0938
0.125	0.0938
0.1563	0.125
0.1875	0.125
0.25	0.1875

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SQUARE KEYWAY DIMENSIONS - IMPERIAL - BS46:1 1958

Shaft Dia Over	Shaft Dia Incl	Keyway Width (B)	Shaft Depth (T1)	Hub Depth (T2)
0.25	0.3125	0.0938	0.047	0.047
0.3125	0.4375	0.125	0.062	0.062
0.4375	0.5625	0.1563	0.078	0.078
0.5625	0.875	0.1875	0.094	0.094
0.875	1.25	0.25	0.125	0.125

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SQUARE KEY DIMENSIONS - IMPERIAL - BS46:1 1958

Width (W)	Height (H)
0.0938	0.0938
0.125	0.125
0.1563	0.1563
0.1875	0.1875
0.25	0.25