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Parallel key calculator: key size by shaft diameter (GOST 23360-78) and crushing check

Enter the shaft diameter, torque and hub length — the calculator picks a parallel key (GOST 23360-78), finds the required length and checks crushing and shear. If one key does not fit, it suggests two.

Round-ended key, working length l_p = l − b. The key is 5…10 mm shorter than the hub, from the standard length series. Use the “key l” field to check an already chosen key.
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How a key joint is calculated

The key section b×h and keyway depths come from the standard by shaft diameter; only the length is calculated, from crushing of the side faces: σ = 2T·10³ / (d·(0.94h − t₁)·(l − b)) ≤ [σ].

Example: d = 45 mm, T = 400 N·m, hub 70 mm → key 14×9×56, σ = 143 MPa ≤ 150.

FAQ

How is a key chosen by shaft diameter?
The section b×h and keyway depths come from the standard table (e.g. 14×9 for d = 45 mm); the length is calculated and rounded to a standard value.
How is crushing checked?
σ = 2T·10³ / (d·(0.94h − t₁)·(l − b)) ≤ [σ], with [σ] = 110…190 MPa for a steel hub.
What if the key fails?
Lengthen the hub, use two keys at 180° or switch to splines.
Why is the key shorter than the hub?
It is made 5…10 mm shorter so it does not protrude.
How is a key designated?
“Key b×h×l GOST 23360-78”, e.g. “Key 14×9×56”.