Shaft Key and Keyseat Size (ANSI B17.1)
The band-table width and H/2 depth machinists mis-read: ANSI B17.1 sets the standard key width from the shaft-diameter BAND, not exactly D/4 -- a 1 in shaft (over 7/8 to 1-1/4) takes a 1/4 in square key, cut to a 0.125 in (H/2) shaft keyseat depth (over-cutting off the full key height weakens the shaft). Key stresses: shear = 2T/(D W L), bearing = 4T/(D H L). At 1,000 in-lb over a 1.5 in key the shear is 5,333 psi and bearing 10,667 psi (both well under a steel key); but a key longer than the hub adds no capacity -- a 1.0 in hub sets the working length, raising shear to 8,000 psi. Square-key model; the allowables and fit class govern.
Formula and source
key_width = standard width from the ANSI B17.1 shaft-diameter band; shaft_keyseat_depth = key_height/2; shear_stress = 2T/(D x W x L); bearing_stress = 4T/(D x H x L).
The ANSI B17.1 Keys and Keyseats standard key and keyseat sizing (Machinery's Handbook), by name; the material allowables and the fit class govern.
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