I'm trying to figure out what size woodruff key to use for the sprockets on the tram. The 'key size vs shaft diameter' table in Machinery's Handbook shows for shafts 7/16'-9/16', use a key of 1/8' width (for a square or rectangular key, not a woodruff), and that corresponds to the width in the sprockets I bought with 1/2' bores. There is no information I can find as to what key length (effectively the diameter of the circle the key would fit into) should be used on what shaft size. Too small and the key might be too weak, too large and the axle would be weakened too much.

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There are several 1/8' woodruff keys, key numbers 403 through 406, with the last digit representing the number of 1/8ths in length, so 3/8' to 3/4' by 1/8' increments.

Metric Woodruff Key Slot Dimensions Chart

What length key should I use? The sprocket hub is 3/4' wide, so it can accomodate any of the available lengths, but I want to be sure that I don't weaken the shaft by cutting too much out.

Woodruff Key Slot Dimension Tolerances

Metric Woodruff Key Set

Steve