I have a problem

[Tom]

I am trying to drill a hole in the center of an 8 inch X 8 inch square piece of glass.  I have only been successful a couple of times, but am actually running at about an 80 percent failure rate due to breakage.

I am using a drill press with a diamond hole bit.  Using as little pressure as I can, trying to take at least 1 full minute to drill the hole, but as said I have only been successful twice.  I have one of those metal burner protectors from a stove turned upside down inside a square baking pan with the glass on top of the burner thing.  I have enough water in there to cover the glass completely, and then some, to keep the drill bit and the glass cool.

Here are some pics. 

Does anyone have any experience with drilling in glass?  Or any tips or tricks I can try?  All this breakage is getting expensive, but it is a project I HAVE to do!!!!

The only thing I can think of at the moment is the drill press runs too fast, and I need to slow the bit down, but I dont know if you can put a rheostat on a drill press to do that or not.  Anyone know? Or know anyone that knows?

[Alan]

Could the problem be the UNSUPPORTED center - have you tried a couple of pieces of scrap glass to support the center on the bottom?

[Kev]

Take the stove burner tray out and replace it with a piece of scrap glass. Place the glass your drilling on top of it and when it gets through that glass you will feel a little pop as it comes out the other side. Also, slightly raise and lower your bit a few times in the process to allow water to get into the hole..don't remove it completely from the hole. I run my Dremmel at 9000 rpm's, so that's pretty fast. I think the problem in the way your doing it now is that there is no support under the area being drilled.

Also, diamond bits do not last that long before they need to be replaced. Each 1/8" of glass it goes through counts as a hole, so if your going through 1/4" glass that counts as 2 holes.

[Wayne]

Try placing a piece of wood under the glass.
Then slow down the drill if you can.
Then use a very small amount of pressure with lots of water..

[JoanFrances]

Tom sooo sorry to hear about your problem with this, but thank you for posting this,  I will be interested in following this thread, as I have never tryed drilling holes in glass, actually I have avoided it by making cut lines where I wanted a hole to be.   

[Kev]

It's really not that hard, but too much pressure will cause it to break.

[PiscesGlass]

I purchased a bit that looks like a diamond coated grinder bit, only smaller, I use it in my regular hand drill, but don't see why one wouldn't work in the type of drill press that you are using.  And I think that they come in two or three different sizes.  I believe I found mine at Warner Crivello. 

http://www.warner-criv.com/product.aspx?id=4180-28

Everyone else gave you good advice, I do pull the drill back and let water seep into the hole as I'm drilling, and the glass is supported underneath it, but so far so good, no breakage.  It does take awhile to do with the method I use.

De

[Graham]

I have a ton of advice, Tom. But everybody's already given it to you. The big problem is the void under your glass. You've been offered a couple of excellent solutions. You'll succeed now.

[ct4mom]

Good Luck Tom, and I'm with Joan, never done it but this sure will help when I do.

[Ian]

Tom
It looks like your drill press is belt driven so you can change the speed by moving the belt to different parts of the pulley wheels. There is normally a chart stuck inside the lid of the pulley wheel housing that gives the different speeds at different configurations of the belt and pulley sizes. Then you need to find the speed at which your particular size drill bit is recommended to run. Normally this comes with the drill bit in a chart form. I was given a tip by our local glass merchant. He told me to drill on a piece of brick which is soaked in water before putting in a pan of water. This gives a solid base on which to drill a hole and also when the drill goes through the diamond edges are automically cleaned and sharpened ready for the next time you need it. Added bonus is that the brick gives a lot of friction to hold the glass steady.
Ian

[Kev]

Won't the brick scratch the glass on top of it?

[Ian]

Sorry
Not face bricks the soft clay brick used for interior walls and no it does'nt scratch I have also used fire brick because I find it easier to cut up on my circular saw
Ian

[Kev]

Ian,

Thanks for the clarification.

[Stephen Richard]

you probably have enough information already, but here is the beginning of 9 tips on drilling glass
http://glasstips.blogspot.com/2008/08/drilling-glass-1.html

[Tom]

Ian, I did check the belts on the drill press, and it is less than what I have found recommended for that size drill bit. 8 mm or 5/16ths.  That was a good tip.

Wayne the wood under the glass would be a good idea, but it will eventually swell and distort and be useless, so I am going to try something like a thick cutting board.  This was a good tip and gave me the idea though, and I will pick one up tomorrow.

Alan & Kev, I have placed another glass under the one I am trying to drill and it still hasn't helped, at least not much that I can state.  I did try 3 more pieces of glass to drill, and 2 broke, so at best I still have a 66 percent failure rate.  I gave up after that. 

De, I would like to try one of those bits, but the 3 on that site are not the right size.  But if I could find them it would be worth a try.  Thanks.

If anyone knows what type of brick Ian was talking about, let me know, I am clueless on that kind of thing, but would like to explore that further.

Thanks everyone for all the tips, I am desperately trying to figure this out..and am very frustrated with it.  Will keep trying though, if you can think of anything else, I am open to all suggestions.

[PiscesGlass]

I'm not sure what type of brick would be used for interior walls, but Firebrick could be purchased from a dealer that sells wood burning stoves..it is a softer brick than bricks used for exterior construction (or walkways).  Might give that a shot.

De

[Rebecca]

Tom, I use a piece of ceiling tile under the glass.  When it gets soggy, I just throw it away and get another piece.  I have heard of using Styrofoam, too, but it tries to float too much for me; I don't like to put extra pressure on the glass to keep it from floating. 

Can you post a picture of the bit you are using?  Maybe that's the problem.  I have used several different bits including a spade bit and a, um, what do you call those hollow ones?  If I just need a small hole, the diamond coated work well and quickly until they get DULL.  (So be sure yours isn't dull.)  They seem to work better at a HIGH speed (10,000 RPM) in the Dremmel.  The larger spade and "hollow" ones are better with a slower speed and taking it very slow.

Rebecca 

[TodB]

Tom:
I'll second or third the above comments; great support is essential as is constent coolant/flushing.
One trick for keeping water in the right spot (until break-thru) is a "tinker's dam". Here, any oil-based modeling clay or putty can be used. Make a little clay dam around the drill site about 1" to 1½" in diameter and put water in there. It will help to have it more localized but you'll still want to "peck" at the glass using frequent withdrawals to clear chips and allow water in the hole. A hand held spritzer can be used to apply more water to the site, too.

The diamond bits with diamond on the sides can be used to enlarge a hole as well. - Tod

[Kev]

How many times have you drilled with the same bit?

[Tom]

Rebecca, you can see the bit in the first 3 pictures above.  It is the hollow core diamond bit.

The ceiling tile sounds like a good idea, but I have so many to do I need something that wont soak up water and get soggy.

Tod, in the pan in the pic above, you dont see any water because I dumped it out to get the pictures, but the water is a good 3/8 inch above the glass when I am drilling, so there is plenty of water for cooling the bit and glass.  To build a little clay dam on each glass I have to drill would be way too time consuming.  Its better and faster to just have enough water in the pan to totally submerse the glass.

Kev, This bit has only been used about a dozen times at most.  I know it is wearing down, but it should still be good for about that many.  They are a little expensive at about $17 each.  I do have one new spare that I will be putting in today or tomorrow.  I am also going to try a silicon carbide spade bit, but think that is going to make a little too much of a mess spraying water around spinning like that as I lower it into the water to the glass.