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Paul Kline | profile | all galleries >> Telescope Making >> Rounding Blanks - Centerless Grinding tree view | thumbnails | slideshow

Rounding Blanks - Centerless Grinding

After trepanning, the blanks needed their rough edges cleaned up. There was some chipping,
fortunately it all was directed out from the blank leaving small sharp projections.
Also, I should have changed the metal on the trepan machine between blanks. It was
so thin while cutting the second blank that it did not hold a good shape and the cut
strayed somewhat. A rounding machine was the answer.
Finished Edge
Finished Edge		 Rounding a 14-inch blank
Rounding a 14-inch blank		 How Centerless Grinding Works
How Centerless Grinding Works

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Paul Kline28-Oct-2007 00:45
Sorry, I have no animations.
>Does the diameter of the rollers matter?
The motor shaft is about 10mm and the skate wheel is about 50mm. I would not go smaller than 10mm for the driver because it takes a beating from the glass and would need extra support. But I did not worry about either of them, so maybe that is not too important. I put a bit of polyethelyne tube on the motor shaft but it quickly was worked off and most of the driving was just glass on steel.
>What if the rollers are replaces by teflon sliders that are concave to approximately match the circle to be turned?
Unless your glass is smooth to start with it will tear up the teflon. Mine was very unsmooth, there is no way it could slide over anything including teflon.
>Then, if there is a notch, it will not cause the replicaton of another notch half as deep when the notch goes over a roller.
A notch would be seen as a low spot. I would expect that the blank would be ground down to the lowest low spot with this system, since everything else is "high".
Thanks for adding a description of your system!

Mohammed 20-Oct-2007 22:12
In your "How it works" page, do you have any software simulations of the grinding action to demonstrate the progress and to help find the best position for the rollers and grinding stones? Does the diameter of the rollers matter? What if the rollers are replaces by teflon sliders that are concave to approximately match the circle to be turned? Then, if there is a notch, it will not cause the replicaton of another notch half as deep when the notch goes over a roller.
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