Hollow Shafting
Hollow Shafting
(OP)
If you were to make a hollow shaft with the following dimensions, how would you do it?
OD - 65.000mm/64.95mm
ID - 56mm/54mm
Length ~ 500mm
There will be no bearings directly run on said shafts. The shafts will be under approximately 50-60 MPa of stress and will be rotating at 2000 RPM.
I have thought about gun drilling a 7075 round and finishing it on a lathe, but is their a cheaper alternative? Nothing is touching the inner bore, it just needs to exceed ~52mm for clearance. I would like to use 7075 or 2024 if aluminum is available. 4xxx series steels are probably my next choice.
Thanks for your help guys.
OD - 65.000mm/64.95mm
ID - 56mm/54mm
Length ~ 500mm
There will be no bearings directly run on said shafts. The shafts will be under approximately 50-60 MPa of stress and will be rotating at 2000 RPM.
I have thought about gun drilling a 7075 round and finishing it on a lathe, but is their a cheaper alternative? Nothing is touching the inner bore, it just needs to exceed ~52mm for clearance. I would like to use 7075 or 2024 if aluminum is available. 4xxx series steels are probably my next choice.
Thanks for your help guys.





RE: Hollow Shafting
RE: Hollow Shafting
RE: Hollow Shafting
I would 2024 only as the last resort.
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RE: Hollow Shafting
Cheers
Greg Locock
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RE: Hollow Shafting
Well I would look at standard tubing, however with an 0.05mm tolerance on the OD you would certainly have to do some machining, why is the OD so restricted? is it, so you can join it to other shafts or just to keep the stress within the range specfied?
I assume the stress range you quote is due to torsional shear stress and not anything else.
If your going to do a lot of these, then Gregs suggestion of an extrusion is the best way to go.
desertfox
RE: Hollow Shafting
Unclesyd, is there a reason you would avoid 2024? Does it not take well to torsional loads?
GregLocock, this is a one off part.
Desertfox, the OD will connect to a flange holding rotor blades. The tolerance is semi-arbitrary. I figured .05mm is tight enough to not get sloppy, but not insane. The stresses come from multiple sources, but mostly torsion. There will be axial lift force and bending moments as well as bolt concentrations, but all of the analysis has been done. The ID is set to just clear another shaft (coaxial).
We are leaning towards drilling with a deep morse taper drill (2 1/8 x 24" long) and then finishing the OD with the ID as a reference. The tolerances for the concentricity are not tight (the shaft just has to clear). We will probably clean up the ID to increase fatigue strength.
Good idea, bad idea???
RE: Hollow Shafting