Attaching cam to shaft

I forgot to mention that the shaft is also in 2 pillow blocks at the other end and in the middle. So there's plenty of support. It's just that I never should have run cold-roll in needle bearings especially under high pressure. (I deserve a spanking!)

Tom,

Is there any reason you can't replace the needle bearings with ball bearings?

If you can, turn the shaft down and put inner sleeves on the needle bearings. For the second edition, if you can, put the sleeves on the shaft and then use some slightly larger needle bearings.

-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works every time it is tried!

Your idea of using a race and boring to accomodate a larger diameter bearing is best. Even a hardened shaft would not be ideal unless it's ground really round. Use the soft shaft and Loctite the race to the shaft. You don't want the race to spin on the shaft. This will also be the cheapest route. ERS

Dummy didn't leave enough meat, but I only have about 1/4" bigger I could have gone. The assembly fits in over-the-river-and-through-the-woods.

The best shaft would be hard on the surface but with a soft core to give good fatigue resistance. Thompson shaft is case hardened and would meet your needs. You could spot anneal the shaft where the cam attaches so it could be drilled for the pin. As long as the end bearing surfaces stay below 250°F, they will retain full hardness. A few seconds heat (dull red) with an O/A torch with air cooling will soften the hard case enough to get a regular high speed drill started. Alternatively, a carbide spade drill will penetrate the case without annealing if heating is a problem. Finally, with a pencil grinder you can can grind off the case in a spot large enough to get a drill started.

Randy

"Tom Gardner" wrote in news:RQnXc.5195$ snipped-for-privacy@newssvr19.news.prodigy.com:

I'd use thompson shaft...ID threaded on the end....then grind a hex or octogon on the end...and broach your cam. Use a bolt and washer to retain the cam.

Thomson shaft works well in needle bearings. The hard case turns nicely with carbide tools, so if pinning worked well before, I'd turn down to perhaps 3/4" where the cam mounts, bore the cam to match and pin it again.

Ned Simmons

Hey Tom,

I've had great luck over the years with McGill Cam Followers. Any good bearing supplier.

Take care.

Brian Laws>I want to attach a cam that is 1" wide, 2.5" dia and attach it to a 1" x 1'

Tom, Try to keep that in another newsgroup please.

Pete

( for the humor impaired.)

But where else would anyone know about leather belts?

I'd consider attaching the cam through the use of a shrink fitting technique.

In essence, this requires you shrink the diameter of the shaft to slightly less than the shaft hole in the cam by immersing the shaft in (ideally) liquid nitrogen or a dry ice and alchol bath. You then QUICKLY position the cam onto the frozen shaft, then simple allow it to warm up.

The method will effectively cold weld the cam to the shaft with no way to remove it except by splitting the came, so position it VERY CAREFULLY on the first try, since there is no turning back to correct an alignment error. A positioning jig is a necessity!

Another caution is accurately sizing the hole in the cam to be just a bit smaller then the diameter of the warm shaft. Too large a hole will result in a poor cold weld, while too small will result in exanson of the shaft splitting the cam. With hard steel, likely a 2-mil or

2.5-mil will be sufficient, but I'd suggest consulting a reference book having shink-fit tables for the correct figures. These also depend on the diameter of the shaft, and the modulus of elasticity for the particular alloys involved.

Done properly, the cam will never rotate on the shaft, and pinning is not required.

Harry C.