Shaft attachment question
Hi, I hope you don't mind if I tag on a related question on mounting a pulley / pinion. (questions are at the bottom of the description )
Similar to groomend, I am interested in mounting a pulley onto a shaft, and it will need to be bored out. There are some details of this seemingly simple excercise that still escape me so perhaps I am over analyzing this.
General Description
- nominal 0.75 or 1.00 inch dia. shaft
- Will hold 3 timing pulleys (AT 10 x 25mm wide x 50mm dia) and at least 2 bearings
- Approx 2 ft long
The shaft diameter was chosen to keep deflection down to the sub 0.010 inch level assuming a 40 Kg / 100 lb load. 0.5 in shaft calculated to a large deflection.
Shaft Selection
- Thompson hardened shaft - seems like a great idea for rotary bearing mounting, but also troublesome for a good hold for the set screw.
- Drill rod - McMaster sells unhardened, but is this ok for bearing mount use ? Straightness is surprisingly less than Thompson shaft.
- Hollow steel shaft - nominal 1 in dia x 0.5 in nominal bore. Sold as a "shim" Seems like a good idea for mass reduction, but the inertial mass would still be similar, and the tolerances are much worse.
- Shaft keyed the entire length - seems like a good idea, but still not all of the pulleys would be able to line in on the keyway and this does not allow for alignment adjustments.
Mounting Methods
- Shrink fit - I need to be able to make adjustments so this is difficult.
- Quick mount pulley devices - basically a collet that snugs up around the shaft inside of the pulley. It seems like a good idea, but at nearly $ 50 / each it needs to be really important, and it is not recommended for highly finished shafts.
- Bearings - 1/2 in bearings are cheap, but 1 in dia bearings are not - ball bearings are at least $ 20 / ea, and commonly 2-3 X this. I am starting to think about using a plain bearing like a bronze bushing / oil lite or Frelon type. I am wondering if this will give more of a stick / slip or not ?
Sorry for the long detail, but now the questions
a) Shaft - Please suggest how hard of a shaft I need for a setup like this. (hobby router use - nominal 5 x 10 ft, 3 hp router)
b) Pulley Mounting - Am I being overly sensitive to the mounting method or are set screws just fine for nema 34 size steppers ?
c) Shaft - Am I correct that a hardened, ground shaft is difficult to attach to or just missing the general idea ?
Thanks
HarryN