Need Advice On Machining Arbor

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horty

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Hi Guys,,, I machined an arbor to fit a .625 motor shaft and hold 2 diamond disks,

I have all the measurements figured out and made an arbor, 2 actually, but the problem is how do I machine a part like this and keep it concentric.

The one in the pic fits well as far as diameters and such but it has a .020" wobble, all directions, I made 2 and they both wobble.

That little bit sure creates some vibration at 3450 rpm.

Could you give me some advice or how to correctly machine a part like this, I know some of you guys are pretty sharp.

Thanks,
Tim
 

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Did you use a 3-jaw or 4-jaw chuck on the lathe?
Does the motor alone vibrate? (bent shaft)
Does it still vibrate without the diamond disks? (just your arbour)
What about with just the long part of the arbour on the motor shaft (no cap, no bolt)?

-brino

EDIT: This document SouthBend Bulletin #7S How to Make Bushings advises on making bushings with concentric OD/ID. Similar.
 
Last edited:
Hi Brino, I used a 3 jaw chuck, the motor shaft is good, use to have a 10" sanding disk plate on it and run really smooth
It does vibrate a little with just the arbor, the fit on the shaft is good it seems, just a light tap and slips on with no play.
With out the cap there is still a little vibration, about 1/2 as before with out cap..

Thanks Brino, nice to talk to you again..
 
I would personally modify the design slightly. Using a 2 piece design as you have shown creates extra opportunities for the blade to wobble. I would try to make the adapter as a flange with a small pilot diameter to center the wheel and threaded bolt holes to screw through the diamond wheels to secure them.

The fit between the shaft and the adapter is critical here. A size on size reamed hole, or at most a .001" oversized reamed hole will minimize the amount of play between the shaft and adapter. The length of the reamed hole should also be maximized (say 2-3 times the shaft diameter) to prevent wobble.

As mentioned above, aim to do this all in a single setup. If you must flip the part, a 4 jaw chuck and a high resolution (.0005 or .0001") indicator should be used to center the part for both radial and axial runout.

At the very end, you'll dress the wheel for running true.
 
I would also make 2 adapters. Each time you mount and unmount the wheel you'll have to dress a fair bit off. Leaving the wheel and arbor connected and swapping them at the motor would help with concentricity and minimize dressing.
 
You woud be better off to make an arbor or bushing for the motor spindle also.
 
JimDawson said:
Do all of the work in one setup, working from the small diameter end. Then part off as needed.
Click to expand...
Not doubting anything, but wont it need to be swapped end for end to do the .625 shaft hole and the other end for the bolt hole..?
 
Sorry , but I think I'm loosing something here on some of these answers, not necessarily you, could more likely be me.
 
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