Drilling Glass (was 'general questions')

We all have had the friend that knows we " do a bit of engineering ". well my latest request is to drill 4No, 5mm holes through a piece of 6mm glass, I have never done this before , so here I am looking for guidance on how to do it and thanking anyone that can help me. Ken.

Can be done with Diamond coated hole saws which go down to 6mm, I have drilled a lot of glass tile and glass mosaic and the odd mirror with them but its quite a slow process. Low speed and trickle of water.

Don't pay the very high prices for DIY shed ones, I use this company in Hong Kong which usually deliver in 7-10days. You will get about one hole through 6mm glass per drill but they are so cheap you can afford to treat them as disposable.

They also do very cheap endmills which are fine for general work or castings that may be hiding the odd hard spot, but best use something better for those jobs that really matter

Edited By JasonB on 06/01/2013 16:58:23

Arceuro trade do some at a good price too.

Arc are still more than 10 times the cost of Richon, About 37p vs £4.20

I've used spear drills like this on glass with some success. Lots of water helps. Best of all is to use the Yellow Pages to find a firm which makes custom mirrors etc, and recommend them to your friend, so even if the glass ends up in shatters, their faith in you won't.

Andy

Hi all

Copper tube in a pistol drill and valve grinding paste works well but a bit slow. The tube can be copper rod of appropriate diameter with a blind drilled hole. Don't try it on toughened glass!

Jim

I've got a vague memory that drilling can be helped making a 'moat' of plasticene or blu-tac around the hole and filling it with an appropriate coolant (I think white spirit but I may be totally wrong).

Neil

The diamond cutters that I use are best with just water but the copper may be better with something else. You can get a special oil for normal glass cutters but I just dip mine in parrafin.

The putty or plastacine dam is a good idea although most of what I drill is already stuck on the wall, so just keep dipping the bit in water. Some of teh tile drill makes also do a little gadget to keep water around the bit.

Ken

My advice is to take a very long time before you get round to doing it - (and, in future be very careful who you choose as friends!) Why is it that as soon as folk hear that you have a workshop they think that you are anxious to solve all their problems? If your "friend" had bought a new vacuum cleaner how would he react if you expected him to come round and clean your house? ( Having said all that I frequently get drawn into those "quick little jobs" for all and sundry )

I don't know about drilling glass but the TC tipped spear point drill referenced by Andyf works very well on tiled surfaces so it stands a good chance on glass. Just be sure that the underside of the glass is well supported and take it easy.

Regards

Norman

I had to do this once and used copper rod drilled out to make a tube I forget what abrasive I used but it was something lying around (probably brasso). Set it up on a pillar drill with slowish speed make the plastercine or blu tak moat and hang a weight off the quill lever. It happens suprisingly quickly (when you're not having to stand over it).

A prominent north American manufacturer of car windows and windshields uses carbide rod drills for drilling mounting holes etc in their products. I've spent some time in their factory. Silicon carbide powdered abrasive suspended in a water and glycol flush cooling solution is used with the carbide drills. The carbide drills are just cylinders, no flutes or holes or grooves. Significant down pressure is used on the drills, over ten PSI at the drill tip I think, the work is well supported directly under the drills, and a flood of abrasive solution provided by several external pipes and jets per drill is used to keep everything cool. No coolant dams are used. The drill is lifted a small amount frequently (peck type cycle) to allow the abrasive and work to be flushed.

I'm told that heat control and the pressure of drilling are the most important parameters. Too much heat and the glass expands locally and cracks.

They do hundreds of holes an hour by these methods, so they have a vested interest in speedy drilling and longest possible tool life. (and fewest possible broken windows!)

Some tool suppliers here in north America carry carbide drill blanks (surprise surprise - they're not all for grinding twist drills out of) which may be useful to experiment with. Could be available in UK too.

Hope the info is useful.

JD

Are you sure that's the right number Jeff? I think we use considerably more than that in everyday drilling.

According to my math (suspect at best these days) a 5mm hole has a cross-sectional area of about 0.03 sq.in. That would amount to an axial force of ~ 5 oz .... not a lot.

According to Tubal Cain ("Drills Taps & Dies"  ) typical axial load an a 3/16 drill drilling mild steel in a drill press would be ~50 lb

Edited By Sid Herbage on 07/01/2013 01:11:24

Did this many years ago when my grandmother wanted a fancy bottle converting into a lamp.

Tool used was a short length of 1/4 inch aluminium rod from an old television aerial chucked in a pistol drill mounted in a vertical stand. Cutting compound was coarse valve grinding paste (it was in the days when you could actually find the engine in your car and take it to pieces) with 3-in-1 oil to thin the paste a little and provide lubrication.

As to procedure I would guess the speed was probably quite high because I don't think the drill had a gear box. I do remember using absolute minimumum pressure, particularly towards the end, and lifting the tool fairly frequently to refresh the mixture in the hole and being surprised at how fast it cut.

The method works because abrasive particles become embedded in the soft aluminium (or copper) and create a grinding tool.

So long as you remember that it is a grinding, not a cutting operation, you should have no trouble. I would suggest have a practice run on a piece of scrap glass then go for it as an interesting (one off?) exercise, provided your friend agrees to accept the risk of failure.

As a one off simply but a set of cheap glass drills, I use a set from Aldi and they are very good. Before starting you need to know what condition the glass is in. If it has been heat treated, toughened, in any way then it will merely explode when you penetrate the outer skin. Not good for the nerves I can assure you. HTH

The copper tube and valve grinding paste works well, it will also grind its way through hardened steel, ie., the face of a cam follower. When I did it, I put several small cuts across the drilling face of the copper tube, and mounted the tube on a bit of steel rod, with a spring between the copper tube and the drill chuck on my vertical milling machine. Set every thing in place with a slight compression of the spring. Can't remember the speed used, could have been around 400rpm. Ian S C

Hi Sid,

I am not positive about the pressure number. I am going from memory and recalling a comment from a setup guy at the factory about the ten psi, some years ago.

Some experimentation would be needed to figure the optimal pressure for the given size of hole and type of glass. Probably best to start off with less pressure rather than more.

JD

Ask the question. How old is the glass. I find that cutting old glass is a hit and miss affair, but new glass is easy peasy. Also, how precious is the job to the 'customer'

Thats where you have been going wrong, never hit the glass

When I use the diamond ones they work best with very little pressure, just let the diamond do its work. I should think it is the same with tehtube/abrasive method as too much pressure will not allow abrasive to get to the end of the tube.

J

Btw. thanks for retitling this thread..( I guess credit to DC1)

As an experiment I tried using a standard carbide tile drill on the bottom of a 'GU' ramekin. The hollow held a little water.

With gentle pressure I got 80% through and was getting cocky and upping the force a little when 'click' a bit broke off inside and four cracks made a star of the base.

I think that a flat sheet, supported on a piece of wood, would have probably drilled OK. I might have succeeded if more gentle or if I had changed sides when just over half way through. I think it was the pressure spalling off a chunk opposite the hole that caused the breakage.

It was a lot slower than drilling through a tile. And more nerve-wracking!

Neil