Drilling your glass reef tank and aquarium using diamond hole saw

Since all materials vary in hardness and abrasiveness, it is impossible to determine exact drill speeds.  Additionally, as discussed below, lubrication and drill pressure must also be considered when determining the proper drill speed.  A faster drill speed or increased pressure may reduce the cutting time slightly, but it will also increase the friction significantly and heat up the bit, reducing the bit life considerably and increasing the risk of heat fractures and material breakage.  If used properly, a diamond drill bit should never be more than warm when touched after use.  If a drill bit develops yellow, brown, blue or black 'burn marks' around the tip, it is an indication of extreme heat and that the drill speed being used is too fast or the amount of pressure on the drill is too great.

When drilling in glass or ceramic, soft ceramic tile and porcelain, if properly lubricated, the dust from the cut should dissipate into the water.  The drill bit contact with the surface should always be wet and the drill bit tip should never be hot.  If the tip is ever more than just warm, it is generally an indication of too little lubrication (or possibly too much speed or pressure).

This discussion is presented only as a guide.  It is almost impossible to have 'too much' lubrication and the only down side risk is the mess from water being thrown off by the bit.  However, 'too little' lubrication will cause many problems.

  Various kinds of very specialized industrial water feed equipment are available for industrial production type work.  But, when drilling with diamond bits, the primary concern is merely getting enough water lubrication on the cutting edge of the bit, no mater what method is used.

   However, all lubrication methods are not equal.  Since good lubrication extends drill bit life considerably, we rated the various methods to help people understand the differences between the various methods.  As a rule of thumb, the relative rating also gives a general indication of the relative drill bit life under various lubrication methods.  For example, the clay dam lubrication method (8 rating) should provide a drill bit life of approximately 4 times that of using a squirt bottle (2 rating).

       Drill bit Lubrication Method                           Rating 1 poor-10 good

Squirt Bottle                                                             2                                                                   

Hose                                                                         4

Clay Dam                                                                 8

Under water                                                            10

Water Feed                                                              10

Pumping Action                                                      10

The most basic method is to use a small hose that runs water onto the surface near the hole and down into the bore hole.  To provide lubrication on a horizontal surface, one trick is to place a plastic jug or bottle with a small hole near the bottom of it, next to the drill hole.  The water leaks out of the bottle and provides continuous lubrication as you drill.  To allow lubrication to reach the drill tip, it is important to use a "pumping" technique described below.  Without the pumping technique, the water rarely reaches the very tip of the drill bit.

Another excellent lubrication technique is to build a "dam" around the drill hole using a small amount of modeling clay or a similar material.  This method is very effective, especially if the water extends above the side tip lubrication hole to allow water to flow into the bit providing good interior lubrication.  "Pumping" the drill will also increase the lubrication at the tip.  The clay can be used many times if it is stored in a plastic sandwich style zip-lock bag to keep it from drying out.

 When drilling on vertical surfaces, about the only way to apply water is to use some type of hose.  If that is not possible, a marginally effective solution is to have someone constantly "squirting" water into the bore hole using a squirt bottle.  Squirting water will usually keep the bit from burning up, but unless a pumping action is used, the water rarely reaches the very tip of the drill.

No matter what lubrication method is used, a periodic "pumping" action will significantly improve lubrication at the drill tip.  Because of the pressure on the drill tip, water has trouble reaching the very tip of the drill bit.  A "pumping" technique allows lubrication to reach the very tip.  While drilling, merely raise the drill up and down a fraction of an inch once in a while as you drill (maybe every 20 to 30 seconds or so).  This assures that water enters the drill tip area completely and fully lubricates the very tip.

Drill Pressure

When using normal drill bits on soft materials such as wood, increasing the pressure causes the bit to drill faster and has little affect upon friction or heat build-up on the bit.  When drilling in harder materials such as hardwoods, it is more important to reduce the pressure and let the bit "drill at its own speed".  Otherwise, friction will quickly burn up the bit.  When using diamond drill bits, the affect is similar to hardwood drilling, but it is magnified many times due to the extreme hardness and abrasiveness of the material being drilled.

When using diamond drills on glass, ceramic or porcelain tile, limestone, marble and granite, etc, it is very important to have only light or no pressure (weight of drill)on the drill and to let the bit "drill at its own speed".  Increasing pressure will not speed up the cutting noticeably, but it will increase the friction considerably and quickly cause the bit to overheat.  This not only burns up the bit, but it also heats up the surrounding surface and can cause heat fractures or breakage to occur.

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If a hole is being drilled completely through a piece of material, it is also important to "lighten up" considerably on the pressure when the drill bit is near the back of the material.  This reduces chipping or fracturing on the back of the material when the bit emerges from the back.

Balancing Cutting Speed,

Drill Speed, Pressure and Lubrication

The cutting speed and life of a diamond drill bit are affected by the hardness and abrasiveness of the material plus the drill speed, pressure and lubrication.  Experience with a specific material quickly allows a person to determine the optimum drill speed, pressure and lubrication to obtain the fastest cutting speed with the least affect upon bit life and risk of heat fractures or breakage.  However, when experience is lacking, it is best to start out with a very slow drill speed, very low pressure and lots of lubrication.  This starting point reduces risks to a minimum and extends bit life considerably.

Starting a Core Drill Bit by Using a Template

Core drill bits above 1/2" work best when used in a drill press rather than in a hand drill.  Starting a core drill bit when using a drill press is simple, since the drill press keeps the drill bit from moving about.  To reduce drill bit slippage or "walking" when using a hand drill, a template can be made to help start the drill bit if necessary.

A template is made by drilling a pilot hole in a piece of soft wood or plastic, using the diamond core drill bit or by cutting a "V" in the edge of a piece of wood or plastic or drilling a hole in it the size of ther core drill.  The hole template works best, however, the "V" template is easier to make and can be used with many sizes of core drill bits.

Templates are often made of 1/8" plexiglass, 1/8" pressed wood or even cardboard.  For repetitive drilling, a plastic or plexiglass template works best since water lubrication can be used immediately.  The template is placed on the surface of the material being drilled, with the pilot hole or "V" above the target hole area.  The template will hold the core drill bit in place as it starts.  After just a few revolutions of the drill bit, a groove is created and the template can be removed.

Using a drill press is easiest, but if this does not work, I recommend using a cordless drill. I haven't found a corded drill which offers good enough speed control.

Glass Block Drilling

Drilling in glass block is basically no different than drilling in normal glass.  If you keep the speed down, use low drill pressure and plenty of water for lubrication, you won't have any problems.  However, there are a few very important facts and tips that will help people in their task.

There are numerous different types and styles of glass block made by many different manufacturers.  Most have some type of design or pattern, however, for drilling purposes, there are two very important characteristics to be aware.  Glass block varies significantly in the thickness of the glass wall and also by how tempered the glass is.  This information is rarely disclosed on the block itself, but should be considered when buying glass block for crafting purposes.

If you are drilling glass block that has been installed in a wall, you don't have much choice but to drill whatever is there.  However, for craft projects, it is good to be very selective.  If the glass block is 3/8" thick, it will take three times as long to drill compared to block with a 1/8" thick wall.  Additionally, it will triple the drill bit wear per hole, causing the bit life to be only one-third as long.

Tempered glass is sometimes used in glass block to increase the load bearing capability of the block.  Tempered glass has differing degrees of temper, and while it can be drilled, it should be avoided if reasonably possible.  Tempered glass block can increase drilling times by 200% to 500% or even more, when compared to standard untempered glass.  Additionally, depending upon the degree of glass temper, drill bit life can be reduced by 80% to 90%.

Experienced crafters who work with glass block eventually learn to search for different types and styles of glass block to test.  After drilling a sample of each block, it is obvious which block has a thin wall and which block is untempered.  Also, crafters who are drilling lots of glass blocks, normally develop some type of pan drilling method, so that the block can be drilled under water to improve lubrication and extend drill bit life.  The "clay dam" method of lubrication is also very effective for drilling in glass block.  "Pumping" the drill is also very important since even under water, the tip of the bit will go dry after drilling about 1/8" deep. 

Glass block normally has a vacuum inside.  Some of the water and glass dust will always be sucked inside when you break through.  But, it is easy to rinse out the inside of the block with water as long as the dirty water is not allowed to dry out.  The plug from the hole will sometimes be pulled into the block, but it will usually drop out easily when the inside is rinsed.  However, if too much pressure was placed on the drill as the hole breaks through, it can cause the plug to have a flair from the splintering on the rear of the hole.  Normally, you can remove the plug with a pair of needle nose pliers, but the best solution is to reduce the drill pressure to avoid splintering as the drill breaks through.

A Few Final Glass Block Tips

A piece of wire from a regular coat hanger or small dowel works great for inserting into the hole to "push" the lights around inside the block, so that all the corners are filled with lights.

A hand drill works fine using a starting template and a clay dam - for a few glass blocks.  However, an inexpensive drill press is well worth the cost if you are making lots of blocks.  There are many very nice, inexpensive drill presses available these days and they make glass block drilling fast and easy compared to a hand drill.

A 1/2" diamond core drill bit works well, is about the right size and seems to be the most popular size for glass block drilling.  However, we prefer a 5/8" bit, since the slightly larger hole gives a little extra room when inserting the lights, pushing them around or to easily remove them if you change your mind (or need to change a bulb).