Making pulley flat

This topic has 5 replies, 5 voices, and was last updated 8 April 2016 at 18:59 by frank brown.

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7 April 2016 at 19:22 #233697
David Brown 9
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@davidbrown9
Hi, I have made a rotating turntable for making a telescope mirror. The turntable needs to rotate evenly with very little or no runout.

I was getting a lot of runout. I have figured out that this is due to the 8 inch pulley I have used to attach the shaft to a the wooden turntable I made, which is 20 inches in diameter. The pulley fits well on the shaft. However, the top of the pulley where I attach it to the turntable is unven, one side is higher than the other.

I am trying to make the pulley even by attaching a file to a vice, leveling it over the pulley and rotating the pulley on the shaft, using a motor at. around 25 rpm. This seems to be working, slowly. The pulley is metal, I am not sure what metal.

My question is, is this a good way to do it? Of course the file is going up and down with the motion of the pulley as it goes round.

I have a milling machine but no lathe.

David
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7 April 2016 at 19:22 #8090
David Brown 9
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@davidbrown9
7 April 2016 at 19:34 #233698
Frances IoM
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@francesiom58905
if you can fix the pulley shaft normal to a flat level surface could you not attach a paper ring to inner and outer edges and fill ring with self levelling ‘screed (eg plaster of Paris) you might need to vibrate at first or apply in thin levels to avoid air bubbles
7 April 2016 at 19:35 #233699
Ed Duffner
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@edduffner79357
Hi David,

If I understand correctly your pulley has a thicker edge or high point on one side causing a wobble of the wooden turntable?

I you don't have access to any machine tools you could correct it the way you are doing it. But how about instead of removing the high point, could you add packing to the low points where the pulley attaches to the wooden turntable?

Have just seen Frances' post and it's a good idea as it supports the turntable across the whole surface.

Ed.

Edited By Ed Duffner on 07/04/2016 19:40:36
7 April 2016 at 19:50 #233704
Steve Withnell
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@stevewithnell34426
Probably missing something basic, but can you not mount the whole lot on the milling machine bed (without the wooden turntable) and take a cut off the pulley? Don't know if the motor has enough power, but having the pulley rotate under power might make for a very simple operation. This approach would mean you could probably do this with quite a small mill. Difficult to know without a photo of the set up.

Steve
8 April 2016 at 18:59 #233820
frank brown
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@frankbrown22225
If the wooden disc is held on by screws going through the pulley flange, just loosen the screw(s) on the "low" side and insert a shim (piece of post card or a bit of a coke can?), then retighten screw.

Frank
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