Oh -- And before anyone else brings it up, the 'pins' are the cylindrical ... -ish ... thingies (that's an engineering term, plural of thingy). Them lo ng narrow ones that are parallel (lengthwise) to a shaft are called 'keys ' - load is distributed to the pin/key based on torque of the shaft (roun dy-roundy force) and the pin's/key's ability to 'handle the load' depends on the surface area and % of it that's 'normal' to the force. longer key s can have more load bearing surface area than you can get from a pin -- pretty quickly the pin diameter eats away too much of the shaft so it fai ls before the pin (this is generally a BAD thing) ...
... this list has some sharp folks with their own engineering backgrounds and I figgered I'd mention my over simplification before someone else ca lled me on it ...
phew.
Bob Hillery Stratham, New Hampshire, USA (and yes, anal-retentive does have a hyphen: ask an engineer and they'll tell you it's part of the load bearing safety factor ...)