Cutting glass discs

[Ian B]

Anyone have any suggestions on how I can cut a disc of around 40mm diameter out of a piece of 4mm or 5mm thick window-type glass? I need the disc itself, not the hole.

I've heard of using a copper pipe in a drilling machine, with an abrasive slurry to grind through the glass - any experiences with this method? Other suggestions?

I only need 1 or 2, so buying a suitably sized diamond core drill is out. The disc will be epoxied into a metal holder, so I'd like it to be within about 1mm on diameter.

Thanks,

Ian

[Dr. Rob]

I know exactly how, Ian... Put your tools away, go to the store and buy replacement lenses for those oxy/ace welding goggles. Dirt cheap, thick, laminated IIRC, but don't recall the exact diameter. That's what I did; it was a lot easier.

(No? How about lenses from cheapo flashlight?)

BUT that isn't what you asked. You're right-- The trick was to put a soft metal (or plastic?) tube in the drill press. Add grinding paste to the rim of the tube. Put the drill press on slow revs, and hang a brick from a string tied to the drill press arm. Apply to glass, and... go have coffee. It'll be done when you get back.

I think this trick came up on the board when someone needed to drill a small hole in hardened steel. Recipe was same, but with wooden dowel.

[WJHartson]

I agree, you should be able to purchase something in the size you need cheap. Flashlight lenses, watch lens, as stated OX/ACET lens.

Joe

[Ian B]

Thanks guys,

Yes, I know the easy way is to buy the glass discs (and I may end up doing that), but I like the challenge of doing it myself - anyone who does machining for a living would probably never consider doing this themselves, but it's a hobby to me - and time isn't always of the essence. Next time, I'll probably want to bore a hole through a sheet of glass and keep the bit with the hole rather than the disc...

I like the weight on the drill press handle idea - I'll give it a go.

Thanks,

Ian

[aboard_epsilon]

hole saw with diamond edge .
and plenty lube
all the best.mark

[Dr. Rob]

PS. Ok, you know what you are doing but I just thought I would say that I am sorry to have given you some erronious info. The gogle lenses are diameter 49.6 mm x 3.5 mm. Good luck anyway!
Doc

[This message has been edited by Dr. Rob (edited 12-23-2004).]

[Rustystud]

Check with your better glass suppliers. There is a diamond tipped scribe that can be mounted to a suction cup disc. The radious can be adjusted for any size. You etch the glass then break away the excess. Most quality glass suppliers can do this for a nominal charge. The small size you are talking about could most likely be made from scrap. If exact size is important get it cut a little over sized then use a belt sander with a fine grit to finish edge down to size. Keep it rotating you dont want any flat spots.
Good Luck

[tonydacrow]

Here's how I've done it in the past.

1. Buy a cheap hole saw (you're going to ruin it) of the size required and move the center twist drill bit so that it doesn't hang down but can still be used to spin the hole saw.

2. "Glue" the glass plates together with warm roofing tar thinned w/ turp.

3. "Glue" an additional waste sheet of glass on each side of the glass you intend to cut. (You don't actually need the two waste pieces if you are careful. However, they prevent chipping on the edges if you go a little too fast.)

4. Clamp the glass onto some wood affixed to the table of a drill press. (You can do it w/o a drill press but you're more likely to chip or crack the glass.)

5. Make a dam of plasticine clay around surrounding where you intend to cut the glass. (If you use regular clay, it may dissolve in the next step.)

6. Sprinkle abrasive powder (carborundum works very well and is cheap) into the damn and add water to make a slurry.

7. Start the drill press at an appropriate speed for the size of the hole (slower than you think) and bring the saw down GENTLY onto the glass.

8. Keep a light but steady pressure on the hole saw.

9. Keep going until the hole goes all the way through.

10. Warm the glass in the oven until you can remove the plates form one another

11. Clean the tar from the glass.

12. Enjoy the glass circles

[Allmetal]

This is the method I have using and it works quite well and is fast once you make up the fixture. I took a 3/4"X 6" round piece of wood and chucked it in my metal lathe in a 3 jaw chuck and made a clean cut to make sure it is flat and then sanded it smooth. I than made up a spring loaded wooden puck that fits in the tail stock and will hold the square blank of glass against the wood in the chuck. I then used a blind ended tube mounted to the tool holder in which I place a new glass cutter. I layed out different circles on the wooden circle so I can cut to different diameters as were needed. With the lathe off and not in gear I mount the glass between the wooden circle and the puck so it securily held, I then crank over the glass cutter mounted in the spring loaded tube until it makes a firm spring pressure against the glass and with one hand guiding the cutter and the other rotating the chuck 360* cutting the glass to the desired diameter using the lines layed out on the wooded disc. Don't over rotate since this will dull the cutter when it recuts the glass. I have cut hundreds of glass circles using this setup and know it to work. I have cut as many as 30 3-1/4" circles in about an hour with no problems or breaks. I have also cut as small as 3/4"circles used in oiler sight glasses with is set up. Bob

[This message has been edited by Allmetal (edited 12-23-2004).]

[wierdscience]

Check with your local glass shop(if you have one)mine got me some 1-3/16" discs for $.85 each,polished edges even.