I have a problem

[Kev]

How much pressure are you putting down on the bit?

[Tom]

doesnt feel like much Kev, it is taking close to a minute and a half to drill before breaking the glass or drilling thru. so I am taking my time, and I do lift the bit out to let the water flush the hole a little,,,up and down, slowly like someone said.  A little pressure, let up, little pressure, let up,,,,and so on.

How many times do you think I should be able to use one bit before replacing it?

[Kev]

That varies from brand to brand and probably even bit to bit, as well as the thickness  of the glass.

[Rebecca]

You REALLY have to go slow and not try to rush the larger bits, both spade and hollow core.  What size hole are you wanting?  Sometimes I think it's better to make an initial hole with a small diamond bit, and enlarge it until you can use the smallest grinder bit to bring it to the size you need.

Rebecca

[Rebecca]

Oops, and I use the ceiling tile for a LONG time after it gets mushy.  Just so it is still supporting the glass off the bottom of your pan.

Rebecca

[Stephen Richard]

Spade bits are so last century.  Really, they are not worth the effort of trying out.
A solid bit of timber will give the support you need under the area where the hole is being drilled.  Also you can put gaffer tape on the back to help with the prevention of break outs.

[JoanFrances]

what is "gaffer tape"?  new term.  To lazy to look it up

[Ian]

Joan It is similar to masking tape
De The clay bricks I am talking about are used here in SA to build interior walls that are plastered over. I forgot that most houses in USA are timberframe houses. Interior clay bricks are made from a red clay usually and they are soft enough to rub on concrete to make a powder Actually we have very few timber houses here.
Tom I must echo what Stephen said about spade bits They are actually designed for drilling ceramic tiles.
Ian

[JoanFrances]

thanks Ian.  Could duct tape be used as it holds up to water, while masking tape doesn't.

[Stephen Richard]

I made a mis-spelling, it is Gaffa rather than Gaffer - which means the boss on a job in additon to the glass making use.
Gaffa tape is not like masking tape at all.  It is in fact duct tape. Now you all know what it is to use brand names that apply only in one country
:-)

[JoanFrances]

Well now, that reminds me of how words in different languages mean something completely different in another language.  As a young teen I recall having a conversation with a friend and in the presences of another young woman who spoke broken English, while we were at the pizza place.  Her face became very red, and she was very upset, because what I had just said to my friend. was very offensive in the young woman's language.  Darn I can't recall what it was I had said, but it had something to do with what I wanted on my pizza

[TodB]

Don:
I see your point about too many dams.
Since you are reasonably intelligent and have produced many successful glassy projects, we can assume that you are totally capable of doing this. So, I'm surprised we haven't hit on a cause for your problems and its solution.

You're drilling slowly and clearing the grit often (often, often), you have the high RPM's needed for this type of bit, you have adequate support under the glass (and don't move it around while drilling!) and you have plenty of water where the action is.

Therefore, I'm going to reach for another explaination... how true does that bit spin in the chuck? If you can see any wobble, that could be a cause of breakage. I currently work in a machine shop which specializes in hole-making, so I may have finally found a way to use all that experience for good!!

Also, what size hole are you trying to make?
Later - Tod

[Stephen Richard]

Contrary to my expectations, I have found that a slower than recommended speed with thinner bits to be successful.  This came with having to do over 500 holes recently.

[Tom]

Well, the glass is still breaking. Have now gone through a little over $100.00 worth.  Got a lot of nice scrap though.

I really am at a loss.  I took care of as many of the suggestions as I could think of, but still no luck.  I think I am going to have to give up on this project and refund a whole bunch of money.

Thanks for all the tips anyhow.

[Kev]

Might be worth your while to get yourself a Dremmel with a flex extension or the drill press stand. I use it quite successfully.

[Glassic]

http://www.youtube.com/watch?v=RIOiwg2iHio&feature=related   

[Rebecca]

What kind of glass are you drilling, Tom?  I practiced on scrap window glass until I got it down.  And by now you probably need a new bit.

Rebecca

[Graham]

What kind of but is that, Tom. I doesn't look like any bit I've ever seen or used for glass. The "diamond grit" looks much rougher than I've ever used.

[Kev]

I agree Graham...looks like the bit is the problem. It doesn't look like any I've seen specifically used for drilling glass. Try a hollow core bit. Diamond Tech makes them.

Check this out.

http://www.delphiglass.com/grinder-bits-disks/drill-bits/

If you cannot get the exact size you need, you can always enlarge it with a small grinding head.

[Rebecca]

Let me see if I can find the one I used and take a picture of it.  Be back...

Rebecca