# cutting Glass Disks



## Ken I (May 26, 2012)

I needed to make a couple of glass disks for my levitating motor. All attempts with a diamond coated hole saw resulted in disks that could be done better by a neolithic flint knapper (Photo - bottom right).

I eventually succeeded (Photo - Top right) by first glueing scrap pieces of glass with cyanoacrylate to either side of the target piece.







The rubber ring was also glued down as a coffer dam to hold water / coolant (you can use modeling clay).

First attempt failed along with the adhesive - you need to let it cure for about an hour.

Second attempt - much better - but my drill press chuck does not run very true - transfered to the minimill where I finally succeeded.

You do not have to apply a lot of force - being particularly prudent at the breakthrough's. Make sure the glass is spotless in order that the superglue layer is very thin (dust specs will increace the thickness).

The diamond bit went through about 10mm of glass in under a minute at about 500 rpm.

After removing the three layered glass sandwich from the bit, I heated it (slowly) with a propane torch until the glue decomposed - cleaned the disk up and voila.

The sacrificial glass should be thiner than the target glass - I noticed a tendency for the thinner glass to crack on heating - probably due to differential stresses and the splintered edges.

Ken


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## Omnimill (May 26, 2012)

I had the opportunity of a show round at a small company that made a variety of glass components, amongst them glass discs. Float glass was first cut into squares then had the corners "knibbled" off. A stack of 20 of these blanks were stuck together with wax and then it was turned between centres on a conventional lathe to finished size. I didn't think to ask what type of toolbit was used!


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## rhitee93 (May 26, 2012)

Nice work Ken


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## Lew Hartswick (May 26, 2012)

Ken, Was the chipping (when doing just one layer) only on the breakout side? If so
I wonder if working from both sides would solve the problem. I realize it would require 
an accurate fixture to locate the work etc. 
  ...Lew...


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## Ken I (May 27, 2012)

Lew,
    The chipping occured on both sides (you can see this on the "bad" disk in the photo) - hence the sacrifical glass on both sides.

Since I obtained better results on my minimll - because of greater concentricity / squareness of the cutter - it might not splinter on the "in" side - I haven't tried it on the better machine since discovering this.

Ken


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## tel (May 27, 2012)

Excellent result! Something to tuck away in the notebook for future reference.


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