Drilling Holes in Glass?

[bid]

Need some advice on drilling holes in glass. I have some holes that need to be opened up from .250 dia. to .281 and I have to drill some holes .312 any advice would be appreaciated.
Thank You
Doug

[Doug_C]

In the archives of the old site, there were a few discussions on drilling holes in glass. I think one mentioned using copper tubing and diamond abrasive compounds to basically lap through the material.

Here is a link to one process. Do a search on the web for more.
Cold working glass

DC

[Roy]

I have used brass tubing, that I made a plug for in one end. Made just a slight notch in the other end, and packed the tube with valve grinding compound. Chucked it up in the drill press and used a piece of rubber to place glass on and started to bore the hole. As the friction heated up the tube it caused the valve grinding compound to expand and flow out the bottom of the tube, initially through the notch but eventually it gets embedded in the tube end and wears through the glass.

I have also heard of using a solid brass rod, with valve grinding compound, and a dam made of putty filled with kerosene and valve grinding compound. Raise rod periodically to trap grit under rod and apply pressure, raise quill and rod and lower again until you eventually wear a hole through.

[timekiller]

I don't recall information very fast any more. My uncle was a monument man and shared some of his knowledge one day in a visit. He said to get a sheet piece of rubber and cut a hole in the rubber you desire. Glue the rubber sheet to your project and then blast away. This is how granite head stones are lettered. Now this process is not as precise as the lapping. It is fast. Remember the sand will mark or frost all uncovered surfaces. I've used electrical tape and played with some drink bottles. I was amazed how fast it cut through the glass bottles. Also, the bottles were more fragile after cutting, and especially after frosting the whole bottle with the sand blaster.

Be Careful & Safe! [img]/ubb/images/graemlins/cool.gif"%20alt="[/img]

Good Luck!

Ray

[WSHBaker]

First answer: Very carefully! Avoid forcing the cut.
Water as a coolant and fine grit silicon carbide (auto supply store).
Tools of copper or brass. Moderate speed, faster for small holes slower for large. It depends on how many holes you have to enlarge and how many to drill from scratch.
At one time I cut 2 telescope mirror and tool blanks from 1" plate glass with a coffee can, abrasive, water, elbow grease and a whole lot of patience. Recently cut an hole in the bottom of a toilet water tank with a 3/4" copper tube, abrasive and 'egg beater' hand drill. Good luck. s/Stan

[Steve_in_Mich]

I have had some success using this type of carbide spade drill bit (not the Harbor Freight variety - and a bit more money). Drilled holes in glass jars for birdfeeders using this type and got 5 out of 6 drilled. Sixth one had to be recycled. The 1/4" size might work for you, as I remember they yield a slightly oversize hole. GLASS DRILL BITS Local hardware may stock the 1/4"

[stephen Thomas]

"National Diamond Labs" Peekskill, NY 914-737-3774 sells all sorts of small diamond tooling. I use their core bits for granite, and have used them for glass. I am not real proficient (read:Impatient!) on glass. The core bits drill pretty fast and smooth, but you have to let up pressure as it nears cutting through, or the backside will spall out and be rough. Never broke any glass this way, just some occasional rough exit sides. I have a dedicated drillpress set up with a water inducer that I made, and a guide with interchangeable bushings for the longer core drills. the short ones you can run right in the DP. They will ask you what kind of shank you want. I strongly reccomend either building a coolant inducer and using screw on bits if you plan to do a lot. Otherwise, get a straight shank, and drill in a lake with a lot of up and down pecking to get the water to the edge, as others have noted.

I tried the brass tube and silica (valve grinding compound) in a lake method a few times on glass. It works, but impatience always got the best of me.

In 1998, a 3/8" diamond core bit was $57, and a 3/4" was only a few $$ more. They do make custom sizes, and custom tools. They once made some diamond jig saw blades for me for a Bosh (recip) jigsaw to make contour cuts in granite. Those were only $17.50 each. They cut moderately fast and last a long time with water. smt

[artk]

I agree with everything regarding using silicon carbide, some metal tubing for coring, and water. Besides not forcing the cut, do check for heat buildup. If you create too much heat, too quickly, the glass might crack. This is more of an issue for thick glass. Take your time and have patience. That said, I am amazed at how fast this process goes. You can notch the tubing if you want which allows fresh grit to get to the work, but I am too lazy to do it and it still goes quickly.

Often pull the coring tool back and add abrasive and water, and then continue.

Regards,
-Art K

[artk]

Great point about breaking out chunks on the backside of the glass. The usual method is to stick another piece of scrap on the back. Us ATM's (Amateur Telescope Makers) usually use pitch or beeswax to stick them together. This the is same issue in drilling through wood or metal for a clean exit hole.

You also might want to chamfer the hole's edge on each side afterwards. You could do this with a solid piece of metal tapered and the usual free abrasive grit and water with the tapered plug chucked into your drill press.

Regards,
-Art K

[Ian_Timshel]

Need some advice on drilling holes in glass. I have some holes that need to be opened up from .250 dia. to .281 and I have to drill some holes .312 any advice would be appreaciated.
Thank You
Doug

There is a terrific telescope makers list that is well archived. I built my scope with only the help of the list.. and not a book in sight.. amazing times we live in..heh
http://ca.geocities.com/itschaotic/scope/

The archive will have plenty of references to drilling glass at: http://astro.umsystem.edu/atm/

Hope this helps..
Cheers! Ian.

[gmac]

If this is a relatively thin item like 1/4 or less in thickness, enlarging the existing holes might easily be done with a dremel and a diamond bit. polish using cratex wheels or sticks in the dremel also. this works great for cleaning up chipped areas in glassware and dishes as well. if the holes have to maintin a true axis or be fit to a mating part, you may need to set them up on some type of holding machine and probably hand or machine-lap them to fit.

drilling the new holes is the challenger, you could probably use the old indian method of the bow and stick in a puddle of sand and water if you wanted, we know that way works. otherwise, it makes a lot of difference if the holes have to be precision sized and located, trued, polished, what kind and age of glass, what kind of fit to a mating part, what thickness of glass, etc. this makes a difference as to what method might get you there the easiest.

be very careful with any glass dust or grit residues resulting from this work - it can be very painful if you get it on your fingers and then do something casual like rub your itchy eye. you need to maintain safe environment with eye and respiratory protection if you do anything with dry grinding, and always use eye protection when using any machines. cleanup often if the work takes a few separate steps, and very thoroughly at the end of the work, selecting the work area so you can control the glass dust easily. gloves are a really good idea if you are handling any items that can break and form cutting edges. it is nearly impossible to wipe up all the glass dust if you work it dry - takes a good vacuum and then a couple of wipedowns with wet cloth to get it all. that's why most commercial outfits do this wet or in closed cabinets.