why is this gizmo made this way?


Got to messing with a gas engine that has an output flange to stub shaft, which slips into slick (no splines) u joing socket. The shaft is held in place in relation to the socket with a Woodruff key and crosspin.
My Woodruff key is a little wedge thing that looks like a sliver of a circle. Why are they made that way? Looks like it'd be stronger to have a rectangular shaped wedge. Just curious.
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rb wrote:

As a guess - the slot in your shaft is probably circular. (A rectangular key wouldn't fit.) A circular slot will trap the Woodruff key so it can't move or slide out the end of the shaft (assuming a rectangular slot is cut to the end of the shaft).
-- bud--
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rb wrote:

It is much easier to machine the socket in the shaft in a semi circle than another shape. I also would tend to think that you could assure a tight fit easier as well.
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Joseph Meehan

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rb wrote:

Well, you're right about the strength factor. You're just thinking about it from the wrong angle. First, think about how the woodruff slot can be cut into the shaft; a rotating cutter plunged into the shaft along its axis will yield a semicircular groove, and a semicircular woodruff key will fit just fine. Or make the machining process just a little more complex and cut a slot by moving the cutter along the shaft axis and you can use a square woodruff key. Their purpose is to provide alignment between the mating parts, particularly for timing or balancing purposes. The actual clamping is from shaft taper or a crosspin. In some applications the key is counted to shear to prevent damage to rotating equipment in the event of a jam or over torque condition.
That's probably more than you wanted to know.
--
Grandpa

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