Tom Gardner wrote:

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?

P.S. I desided to shelf the AR-15 build, I just don't need it. Thanks for
all the tips though, I learned a lot! I'll post pix of the new machine (8
month build) this month...it's RADICAL, nothing like it in the world!




Just throwing a little fuel on the fire... I have a very old traversing
head shaper where the head mechanism slides via the sliding key in the
shaft method. It's worked for over 100 years with some fairly high
pressures on a 1" shaft and 1/4" gib key. Yes, there is a bit of slop
due to the sliding fit of the key but neither the key nor the shaft
keyway have any specific bend or mushrooming or shearing from the
thrust. It works, although not if you want high precision.

Koz