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Drill bit opinions?

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Maryar
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Drill bit opinions?

Postby Maryar » Fri Aug 03, 2012 9:46 pm

I want to make a lamp. The glass needs to have a 1-1/2 inch hole. I have a 30mm drill bit (a little over an inch) that I have yet to use.
Does anyone here use a smaller bit and then grind it out to size? I'm sure that is more work but may save me some money. Drill bits from glass suppliers are around $30 or more. I'm guessing it would be less from a hardware store but I didn't find one at Lowes.
Is there a difference in quality of the cut from the drill bits from glass suppliers versus hardware stores to justify the price?
Mary

Bert Weiss
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Re: Drill bit opinions?

Postby Bert Weiss » Sat Aug 04, 2012 12:48 am

Inch and a half diamond core drills can cost quite a bit more than $30. Be sure you have a drill press where you can position the drill and glass in the right place. Only once did I try and drill a hole this size using a hand drill. I popped a pretty big and complex glass sink and then went out and bought a tripod drill. I am glad I did because that drill costs a large fortune today, it was a small fortune 18 years ago. It has gotten plenty of good use over the decades.

I bought some cheap Chinese core drills. They came with really short shanks, and the metric sized shanks don't fit inside American drill bit extensions. I could not find any metric extensions for them, so they sit here unused.

You can get a Chinese radial arm drill press for not too expensive as drill presses go. These work, but you have to make every possible adjustment each time you use it.

A good sandblaster can work through a hole, but drilling is a heck of a lot faster and more accurate. If you have a sandblaster and don't have a drilling setup, it would be a solution.
Bert

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Morganica
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Re: Drill bit opinions?

Postby Morganica » Sat Aug 04, 2012 1:58 am

Maryar, I'm not sure where you live, but if there is a Harbor Freight nearby you can purchase a small drill press for under $90--a friend and I got ours during one of HF's periodic sales for around $60. It's not fancy, and it takes a little while to assemble, but as Bert says it makes a huge difference in the quality of the holes you drill. The work is held steady and chipout is considerably reduced.

If your hardware store sells diamond drill bits you could certainly try one on some test glass and see how it does. I generally have better luck with the ones sold by the glass equipment suppliers.

Whether you can grind the hole another half-inch to size depends, I suppose, on how steady your hand might be and whether you've got some kind of cap to cover the uneven edges. I'd be afraid that at some point I'd come down just a bit too hard in one place and crack the whole thing.
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Lauri Levanto
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Re: Drill bit opinions?

Postby Lauri Levanto » Sat Aug 04, 2012 2:57 am

I have to invest as little as possible to tools, because I prefer to buy glass.
For a half inch hole I have to use what I have.
First a 2-3 mm hole with Dremel
Then I enlarge it with the 6 mm extension bit on an edge grinder Glasstar.type.
When I get the bit throuh, I use it as a grinder, moving around until the hole is large enough. I get an almost true circle. Usualy imperfections are covered with the fittings.

I am retired, so I need not make profit. Time is not an issue for me.
In production work priorities are different-
-lauri

Maryar
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Re: Drill bit opinions?

Postby Maryar » Sat Aug 04, 2012 9:39 am

I like drill presses; I have a regular size and one for my dremmel. But I don't think my regular one will go high enough to drill a hole in the bottom of a vase shape. It is an inexpensive one from Harbor Freight. I have kept it in one position so long that I've even forgotten how to make it go up. I'll have to check on how far it can go up.
I've seen a video with the 1-1/2 inch bit and they did it by hand drill. They made it look easy but they probably have tons of experience. I was worried about many things going wrong with using a hand drill from breaking the glass to an accident.
No way to sandblast so that can't be an option for me at the moment.
I have ground out smaller holes to make them a bit larger, but not perfectly round. I was hoping with a larger hole, it would be easier to grind to shape. I believe I would have to look into the vase to grind it. I don't know if it would be possible for me to be directly over my work like that. If I can't look into the vase, I would have to grind a little, take it off and look, grind again, over and over. I don't have a lamp in hand to see if the fixtures would cover a mistake or if the hole has to be exactly perfect.
Would be nice to drill the hole first on a flat piece of glass then slump but I'm guessing that slumping would disfigure the hole. Anyone tried that?
Mary

Bert Weiss
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Re: Drill bit opinions?

Postby Bert Weiss » Sat Aug 04, 2012 12:51 pm

You can probably get creative and make your drill press work. If you rotate the drill so you can make your own table for support, you should be able to function. I would put a 2" x 2" stick of wood inside the vase, upside down, supported on a solid surface, and drill in towards the wood. The critical moment is coming through the second surface. This is where the chip out happens. You want to be using as little pressure as necessary there. If you know how thick the glass is, you can set up a gauge on the drill press that will allow you to lower the bit by rotating the gauge nut, allowing it to go down just a bit more. If the wood does not match the shape of the vase interior, add some modeling clay so the glass is well supported as you drill through.

Old fashioned drills used a brass cylinder bit and silicon carbide grit slurry to cut the hole. These are relatively inexpensive.

You can drill before firing. It will distort the hole, but re-drilling out the hole after slumping is a lot easier than the first time through.

I make a dam using either modeling clay or Mortite window caulking rope. It doesn't have to be too high. It does need to hold water. I also much prefer using just a little diamond coolant in my drilling water. This seems to lengthen diamond bit life. It is not a big surprise that the cheapest diamond core drills don't last long. I have always found the more expensive ones to be more cost effective if you are drilling many holes.
Bert



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Maryar
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Re: Drill bit opinions?

Postby Maryar » Sat Aug 04, 2012 3:00 pm

Good to know that the more expensive bits seem to be the longer lasting. Are they usually a better,smoother, faster cut?
I had not thought about rotating the drill on the drill press. I will have to see if it can do that.
I had thought about needing something inside the vase for support. Good idea about the wood and modeling clay. The only thing I could think of was pouring plaster of paris into the vase bottom. I was thinking that without a release agent it may stay put, but then again, may not. That would make it the exact size of the bottom of the vase. Plaster wouldn't get wet and start dissolving until the bit was through.
A smaller hole before slumping may be the way to start.
Mary

Bert Weiss
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Re: Drill bit opinions?

Postby Bert Weiss » Sat Aug 04, 2012 3:21 pm

Maryar wrote:Good to know that the more expensive bits seem to be the longer lasting. Are they usually a better,smoother, faster cut?
I had not thought about rotating the drill on the drill press. I will have to see if it can do that.
I had thought about needing something inside the vase for support. Good idea about the wood and modeling clay. The only thing I could think of was pouring plaster of paris into the vase bottom. I was thinking that without a release agent it may stay put, but then again, may not. That would make it the exact size of the bottom of the vase. Plaster wouldn't get wet and start dissolving until the bit was through.
A smaller hole before slumping may be the way to start.
Mary
Modeling clay is not hard to clean up from.
The better bits tend to have thinner walls and more diamonds. You can dress them to expose new diamonds.
When I mentioned pre drilling being easier, I was referring to a full sized hole. The shrinkage isn't much. You may not need to redrill.
Bert



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Maryar
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Re: Drill bit opinions?

Postby Maryar » Sat Aug 04, 2012 6:30 pm

OH, a full sized hole. I thought that it might stretch wider with slumping.
Thank you for clarification.
Mary

Barry Kaiser
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Re: Drill bit opinions?

Postby Barry Kaiser » Sat Aug 04, 2012 6:44 pm

I'm another Harbor Freight junky (some of it can be junk, but the cheapo drill press is not). I got mine several years ago on special for $39.99. Now their on special price is either 49.99 or 59.99.
For Drill bits, try ebay seller LAU***. Yep that is their name. I by my small bits from them and they are decent. Also bought some larger hole bits and they worked very well.

Barry

Morganica
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Re: Drill bit opinions?

Postby Morganica » Sat Aug 04, 2012 7:18 pm

Maryar wrote:OH, a full sized hole. I thought that it might stretch wider with slumping.
Thank you for clarification.
Mary

It might or might not, depending on what you're slumping into/over. If it's a relatively shallow slump that doesn't change the profile of the glass (i.e., the thickness pretty much stays the same), the hole probably won't distort very much.

But if it's a deep slump through a drop ring, where the glass is more likely to stretch and thin out, the hole will probably stretch, too. And if the glass around the hole has to curve up or down, that might not distort the shape, but it could reduce or expand the size of the opening.

And you might want to test it on a piece of scrap glass first. The edges of the hole will now heat up as fast as the edges of the blank, and if you're doing a deep slump that might affect the way the glass comes down.

Never set the glass on a hard surface (like plaster) to drill it. You want something that can absorb the additional force if you accidentally come down too hard. That's why I use plasticene (an oil-based clay that won't dissolve in the water). It makes a wonderful cushion and you can also build up the sides around your vase to hold it steady.

Assuming you can get the vase under the drill press head, the bigger issue is usually getting far enough down into a vase with the bit. You can buy a drill extension chuck for around $30, essentially a long tube with a chuck on the end, that can add maybe 8-10 inches to your reach if necessary. They're usually sold in specialty hardware stores.
Cynthia Morgan
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Tom Fuhrman
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Re: Drill bit opinions?

Postby Tom Fuhrman » Sat Aug 04, 2012 8:17 pm

I've had good service with diamond drills from Dan Lopacki, www.lopacki.com, he sells his 1.5" diamond core drill for about $38. I've used them in hand drills and in drill presses.
when starting with a hand drill be sure to start at an angle and them slowly raise the drill into an upstraight position.

Jeanne
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Re: Drill bit opinions?

Postby Jeanne » Sat Aug 04, 2012 10:13 pm

I have a regular drill press and have also used the LAU bits you can get on Ebay. They work very well and I bought multiple sizes because they were so inexpensive. They were strong enough to drill through some fairly thick fused glass as well as porcelain tile. The cut glass does get wedged up in the bit but a finish nail inserted into a side gap will pop it out with a little effort.

Maryar
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Re: Drill bit opinions?

Postby Maryar » Sat Aug 04, 2012 11:03 pm

I'll check the sources listed for drill bit options.
I'm still leaning towards the hole first method. Sounds better than ruining a finished piece. Even with scrap, if I break it in the beginning stages, I can correct my mistakes and easily start again.
I thought more about enlarging a hole with the grinder. I practiced a little today with a scrap bottle to see if standing directly over my grinder looking down into it would be doable. It wasn't an easy position to be in. I need a shorter table or dig holes in the yard to put my table legs into.
I can understand the cushion under glass. I use plastic type of packing foam under my small pieces I drill. You are right, plaster would not do.
Maybe I will try a gentle handkerchief drape.
Mary

Jeanne
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Re: Drill bit opinions?

Postby Jeanne » Sun Aug 05, 2012 7:42 am

I have made some hanging lights from glass draped over the vase mold. The lights were from raked glass so they were fairly thick (6-7mm). If you drill them first and then slump, the hole does get larger (and mine went a little off center). I decided on the second lamp to drill after slumping so I could control it.

Maryar
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Re: Drill bit opinions?

Postby Maryar » Sun Aug 05, 2012 10:27 am

[quote="when starting with a hand drill be sure to start at an angle and them slowly raise the drill into an upstraight position.[/quote]
This seems so strange to me about starting at an angle when one advantage of a drill press is to be able to go straight down. The video I saw also said to start at an angle, they were using a hand drill.
Does starting at an angle help keep things from spinning out of control?
At an angle, do you drill very deep or just scratch it?
Mary

Barry Kaiser
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Re: Drill bit opinions?

Postby Barry Kaiser » Mon Aug 06, 2012 11:03 am

The concept of starting at an angle is really for hand drilled small holes using a flexshaft or dremmel. This is done to prevent the bit from walking across the glass. It is not foolproof and only works a percentage of the time. To overcome this we use a ball bit for a starter hole and then drill with a cylinder bit. We have a tutorial on our web site doing this (see below).
We find our drill press is a pain for small holes. It is sort of like using a sledge hammer to drive a nail.

Barry

Jeanne
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Re: Drill bit opinions?

Postby Jeanne » Mon Aug 06, 2012 11:25 am

I was unable to use a regular drill for a diamond hole saw bit. It just wanted to skitter about and was virtually impossible (for me) to control. The drill press was the only thing that worked for me.

The 'tilt first and stand upright' maneuver works fine for a dremel. But that's when using small 2mm or so size bits, not a hole saw.


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