Drilling through Glass Block

I need to drill a 1/2" hole in a glass block. What drill speed should I use on my drill press? Do I need to cool the bit? Anyone have experience with this?
Thanks,
DUSTY
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On 27 Sep 2004 10:39:45 -0700, Dusty snipped-for-privacy@hotmail.com (Dusty Workshop) scribbled:

You need to get a diamond hole saw, available here (among other places):
<http://www.leevalley.com/wood/page.asp?page2277&category=1,180,42316&abspage=1&ccurrency=2&SID=>
I'm sure the folks at Lee Valley will be happy to answer your other questions.
You might also want to check out previous discussions on Google groups: <http://groups.google.com/groups?as_q=glass%20drill%20hole%20speed&safe=images&ie=UTF-8&as_ugroup=rec.woodworking&lr=&num 0&hl=en>
Luigi Replace "nonet" with "yukonomics" for real email address www.yukonomics.ca/wooddorking/antifaq.html www.yukonomics.ca/wooddorking/humour.html
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Are you using a tile bit? Go slow and use some light lubricant.
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Dusty Workshop wrote:

and rather light pressure...go slow to avoid building up too much heat. HTH
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Dusty Workshop wrote:

Diamond drill, lots of coolant (grinding coolant is best), slowly, or find someone with an ultrasonic mill/drill (I've got one at work), much easier...
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I am using a 1/2" tile bit. I plan to use the drill presses slowest speed. I have a friend who used the same type bit without coolant and had no breakage. The piece of gass is small enough to be manageable. I could put it in the fide or freezer to cool it down prior to drilling. I am going to try the first hole with the piece at room temp and see what happens...
wish me luck...
DUSTY
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Probably not a good idea as the glass will be more brittle. Just use a slow speed, light pressure, and some mineral spirits or kerosene as a lube. Piece of cake.
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Agreed, in fact, I'd suspect cooling the glass first would be a _very_ bad idea. It's not so much the heat from drilling, but more the temperature difference in different areas of the glass. Cooling the rest of it will make that difference much greater.
Now, maybe if you heated the glass first... Nahh, the heat generated by the drilling will cause a rise above any ambient temperature that you have. Just go slowly and follow their advice. GerryG

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