Cutting Glass

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Thanks! I think I'm going to start with the mylar/mount pieces for now, so I can get these mics running. At the degree of stretch required to have the same stiffness of .004" glass, I think the tension will be pretty even. The tighter you stretch it, the more even it tightens. Also, if you heat it up, you can even out the tension before you stretch it out, then it'll be pretty good once it's glued on. You can also adjust the damping of the mics after assembly - the clearance can be changed after the fact.

The second phase is going to try one of the machining methods. I think PRR's suggestions would be good to try. I can certainly do some accurate machining on my lathe, so...  I also have a sandblaster, so perhaps another approach would be to mask a 1/2" part of the glass, and just blast away (slowly) what's left.

The source glass is a #0 microscope cover slip. I tried to find a #0 cover slip in 1/2" round, but could not do it. I can get #1 in 1/2" round, but that's about 0.008" thick. I'd have better luck with Mylar rather than trying to thin out a #1 slip down to a #0.

-Dale
 
Fix the cover slip onto a piece of window glass with some wax, pitch, or other removeable material. Fasten it to your drill press table with the cover slip centered under the arbor.

Cut a piece of  1/2" ID brass or other pipe a few inches long and square one end. Chuck it up. (If you only have a 1/2" chuck, insert another piece of 1/2" OD pipe, rod, or whatever, into an inch or so of the original pipe and fix it with a couple of screws.) Set the speed to low RPMs.

Put some valve lapping compound or other  ~#200 grit abrasive slurry on the cover slip, and slowly and gently lower the spinning pipe onto it, letting it grind its way through the cover slip. You may have to add more abrasive intermittently. This will cut a perfectly smooth circular piece in a few minutes, which can be removed by heating the wax.

Edit - on rereading the thread I see PRR already suggested this. It works - I've cut glass disks up to 5" diameter this way (though considerably thicker.)
 
Maybe one of these will help, depending on the actual ID/OD.

http://www.harborfreightusa.com/usa/itemdisplay/displayItem.do?itemid=32400

http://www.harborfreightusa.com/usa/itemdisplay/displayItem.do?itemid=32399
 
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