In article , "Tom
Gardner" says...
Imagine a 1" dia. shaft driving a #40 chain, 32 tooth, 3.5" dia.
sprocket.The shaft drives a cam that takes 50 ft/lbs torque. The shaft
rides in two pillow blocks and a bearing in a block, all mounted on a 1/2"
plate 12" long. The cam drives a guillotine wire cutter. When I want a
longer cut, I slide the plate and all, up to 1" of movement in slots.

I've used split tapered bushings to mount the sprocket to the shaft and it
works great, but I have to move the sprocket with a size change and
re-timing the cam is a bitch. If I put the sprocket on a key with a set
screw, I think it will booger-up the key and such quickly. Do you think if
I use multiple keys or splines I can let the sprocket float without a
fastener? Timing is +/- maybe 2 degrees. Makes sense to me and that scares
me. If so, how many / how big keys?


I'm afraid I don't have a complete mental image of your mechanism - is
there some reason you can't use a taper-lock or QD hub on a keyed shaft?
The key maintains timing when you slack off the taper-lock to adjust
position.

If you do decide to use a keyed shaft with a sliding fit, besides the
other warnings about wallowing out the keyway, keep in mind that another
potential failure mechanism is the key rocking in the shaft keyseat. The
key should be an interference fit in the keyseat and care should be
taken to make sure the keyseat walls are parallel. A deeper that normal
keyseat (i.e., rectangular key) will also help, but has the downside of
weakening the shaft.

If you go the spline route...
http://catalogs.hubcityinc.com/farmr...roducts.html#2

A sexier alternative splines...
http://www.generalpolygon.com/apps.htm

Ned Simmons