Diamond Core Drills
Diamond Drilling Glass
To achieve the best results in drilling glass the following points should be taken into consideration:
1. A drill press or stand drill will always give better results and longer drill life than hand held drilling.
2. In an ideal world the peripheral working speed of a diamond core drill for glass would be about 5 metres per second, representing about 9500 revolutions per minute (rpm) for a 10mm drill. As most standard electric drills are made to run at a maximum of 3500 rpm it’s clear from this that we can’t achieve optimal drilling speeds until we are drilling with a 28mm drill.
As most manufacturers today make core drills that will operate sufficiently from 1 metre per second we can run a 6mm drill on a machine running at 3500 rpm. Consequently, every drill size smaller than 6mm isn’t running efficiently in a standard electric drill and requires special care, i.e. plenty of coolant (very cold water preferably with a cooling additive), a drill stand or some means of holding the drill in a steady position and sufficient coolant pressure to ensure that the contact area is kept clear of debris.
3. Most drills from 3mm up are core drills, that is to say a drill with a hole in the centre to allow coolant to flow freely. For drills up to 6-7mm it’s necessary to ensure that the core remains free of debris and this can be achieved either by using a high pressure coolant supply or regularly removing the drill from the work to allow the coolant to flush the work area and clear the core of the drill.
4. Don’t forget that you are essentially grinding glass and not drilling in the traditional sense. Your greatest enemy is heat build-up as this will lead to micro cracks in your work and possibly premature drill tip failure.
5. Never drill constantly. Always lift the drill out of the work at very regular intervals, the smaller the drill diameter the more often.
Types of Drills
Sintered diamond core drills, unlike plated drills, have diamond content throughout the tip of the drill, so as it wears down you can run it through a dressing stick and expose new diamonds. This extends the lifespan significantly. Other advantages are apparent in the speed and efficiency of drilling. These drills are the choice of professionals and represent the best value and performance per hole.Advantages:
- Multiple layers of diamond
- Super smooth finish
- Longest lasting drill
- Most cost effective
With sintered drills, it is however important to have a continuous coolant feed through the centre of the drill to prevent damaging the drill and the work. It is also highly recommended that you use a drill press. We offer sintered drills with a Belgian 1/2 inch connection. We also offer adaptors to match your specific water feed system.
Electro-plated drills are a single layer of diamond or CBN, mixed in a nickel bath deposited onto a substrate for maximum diamond or CBN exposure. Diamonds sit only on the surface. When this diamond portion is peeled off, the diamond drill will slow down, drill on the side or stop working altogether.Advantages:
- Least Expensive
- For small volume cost effective
- A little less sensitive to heat build-up
Varying with application and material, an average electroplated diamond core drill will last you 60 to 100 holes. Electroplated drills cost less, and at first glance may seem like the most cost effective alternative. However depending on your application, they will cost you more in the long run.
Solid shaft drills for use in small high speed drills (Proxon or Dremmel). These drills are nickel plated and the best method of drilling is by having the glass submerged in coolant. Be very careful when using electric drills, make sure they are low voltage (with transformer) and well earthed or even better use a high speed air driven drill.
Dressing sticks made from silicon carbide or alumina oxide (soft bond) are usually used for dressing diamond tools. Sintered diamond drills must be used with the diamonds exposed properly through frequent dressing. Otherwise, the diamond matrix will glaze over.
The drill will begin to tear rather than grind which is very destructive. Tearing caused from unexposed diamonds creates friction. This causes uneven wear and heat cracks in the drill as well as the material being drilled, resulting in premature wear and will eventually destroy the drill. The more a diamond tool is dressed the cooler it will drill or cut.
When added to water synthetic water soluble coolant will improve your overall diamond drilling operation by as much as 30%. Plain water evaporates at 100°C. Temperatures at drilling zones reach 250°C.
Water evaporates before it cools the diamond drill & material resulting in shorter Diamond drill life. Use of coolant reduces micro cracks associated with overheating, improves drilling speed, increases drill life and improves surface finish.