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for Diamond Drill Bit Use
Diamond drills bits are used
on glass, stained glass, glass bottles, glass block, ceramics,
ceramic tile, porcelain, porcelain tile, limestone, marble, granite,
slate, stone and fiberglass. Drills used on wood or metal
have a sharp metal tip or teeth, that cut into the material.
These types of drills do not work on glass, marble, etc. as the
tips do not "bite" into the extremely hard material,
and they cause heat build-up that burn up the bit and cause "heat
fractures" in the material.
Carbide tipped Spear Point
drills are sometimes used on the "softer" types of
hard materials - like untempered glass, sandstone and marble
and some of the less hard ceramic and porcelain tiles.
While they sometimes work, they tend to chip the hard surface
very badly, leaving a rough hole and they often cause breakage
due to fractures from the chipping and heat. Diamond drill
bits are designed differently - they have diamond tips that "grind"
into the extremely hard materials.
Spear Point carbide bits no longer work
the new type of super-hard floor, counter and wall tiles.
Drill Bits are the solution.
The sections below discuss the
many characteristics of various materials and the special techniques
needed for using diamond drill bits to drill those hard materials.
The most important factors are to use a slow drill speed (see
speed table below), low drill pressure (see pressure table below),
and plenty of water for lubrication. Drills that have a
variable speed work best because the proper speed can be selected.
Some fixed-speed drills have a minimum speed of 600 or 800 rpm,
which may be too fast for many diamond drill applications (see
speed chart). Also, impact type "hammer drills"
should never be used with diamond drills bits.
Core Drill Bit
Bottom - Blunt Nose Bit
Core Drill Bits
and Styles of Diamond Drill Bits
Diamond drill bits come in many
different sizes and shapes but are primarily of two basic styles,
blunt nose solid bits and core drill bits also
know as hole saws. There are also two basic types
of diamond drill bits relating to the application of the diamonds;
bonded and sistered.
Drill bits that have a solid
tip are often called "blunt nose" bits. They
have diamonds on the solid tip and on the sides of the tip.
This style of bit drills a complete hole by grinding a full hole
the size of the tip. Core drill bits however, are hollow
at the tip. They have diamonds along the edge of the tip
and slightly up the sides of the tip, similar to a margarita
glass that has been "rimmed" with salt. Diamond
core drill bits grind or saw a circle at the edge of the tip
rather than the full diameter of the tip. A core drill
results in a hole the size of the tip and a smaller "core"
or "plug" that comes from the middle of the hole.
Core drills are often called hole saws, since they saw
a circle to create a hole.
Since solid Blunt Nose bits drill
out the full hole, they are only effective for very small holes
whenh drilling in hard materials. The solid blunt nose
style of diamond bit is only available in sizes up to about 3/8"
and they are used primarily on glass. Blunt Nose bits are
not designed for extremely hard materials such as stone or ceramic
and porcelain tile. Core drills only drill out a portion
of the resulting hole - about 10% or less of the hole, so they
drill much faster than blunt nose solid drill bits. The
hole saw style of diamond core drills can be used to drill large
holes and can be used on most non-ferrous hard materials such
as glass, stained glass, ceramic or porcelain tile, ceramic,
porcelain, fiberglass, limestone, slate, marble, granite and
other stone materials.
Bonded diamond drill bits have
the diamonds bonded to the the edges of the drill bit tip, generally
using an electroplate or brazed bonding process. These
drill bits are generally slow-speed bits and are fairly inexpensive.
During use, the diamonds eventually wear off of the bit due to
the hardness and abrasiveness of the material being drilled.
Bonded diamond drill bits must not be used on metal, concrete,
or masonry and they require proper drill speed, low pressure
and adequate water lubrication.
Sintered diamond bits have the
diamonds mixed directly into or embedded in the steel tip.
As the metal tip wears down, new diamonds come to the surface.
Some 'sintered' diamond drill bits are designed for use on metal,
concrete or masonry, however, the specific manufacturer's recommendations
must be reviewed. sistered diamond drill bits are generally
high-speed bits and are somewhat long-lasting, however, they
are also extremely expensive and therefore are use mostly in
The life of any type of diamond
drill bit depends upon the hardness, abrasiveness and thickness
of the material being drilled and the specific drilling techniques
used (drill speed, pressure and lubrication), however, the diamonds
of a drill bit don't actually wear out as much as they
wear off due to heat and friction caused by the extreme
hardness and abrasiveness of the material drilled.
Drilling in glass, ceramic, porcelain,
marble, etc. is a slow process compared to softer materials such
as wood or even metal. A fairly deep hole can be drilled
in wood in just a few seconds, while it may take 20 or 30 seconds
or longer to drill a hole in standard 1/8" thick glass.
In some very hard stones and tiles, it may take 2 to 3 minutes
to drill only 1/4" deep. Using diamond bits to drill
in hard materials is not difficult, however, it takes time.
A person should consider that they aren't 'drilling' a hole,
as much as 'grinding' a hole.
& Abrasiveness of Various Materials
Materials have varying degrees
of hardness and abrasiveness. Additionally, specific man-made
and natural materials can differ greatly depending upon the exact
physical composition. For example, glass varies in hardness
depending upon color and type, since various metals and minerals
are added to achieve the different types and colors. Glass
also has differing degrees of "temper" depending upon
the specific manufacturing methods used. Ceramics and ceramic
tile are various forms of vitrified glass like material.
Porcelain and porcelain tile are essentially manmade stone and
have characteristics similar to Granite. Ceramic and porcelain
also have differing hardness and abrasiveness depending upon
the exact type, composition, manufacturer and manufacturing methods
The hardness and abrasiveness
of natural materials, such as stone, vary by type, but they also
vary significantly within a specific type. Most stones
are not pure - they are mixtures of various types of rock.
Granite, for example, contains various combinations of primarily
quartz, feldspar, black mica and hornblende. Therefore,
a specific stone type such as granite will vary significantly
in hardness and abrasiveness depending upon the exact mineral
composition that varies by quarry location.
Below is a table of the hardness
of various materials. The table uses the standard Knoop
Hardness Scale (kg/mm2). The hardest known material is
Diamond, with a Knoop measurement of 7,000. On the Knoop
scale, a material with a hardness of 400 is four times as hard
as something rated as 100. Tungsten Carbide, used in carbide
drill bits, is the hardest natural material next to Diamond.
However, with a Knoop measurement of 2,000, Tungsten Carbide
is less than 30% as hard as Diamond.
Wood - Pine
Porcelain Fixtures & China
Ceramic Wall Tile
Porcelain Floor Tile
Style Porcelain Floor Tile
Granite Style Porcelain
125 - 150
140 - 180
140 - 250
400 - 550
450 - 550
500 - 650
500 - 650
550 - 650
Reprinted with permission
Use and Reproduction is Restricted
Speeds for Diamond Drill Bits
Diamond drill bit speeds vary
depending upon the manufacturer and type of diamond drill.
Glastar Blunt Nose solid Diamond Drill bits, designed for use
only on glass, can be used at high speeds up to about 10,000.
However, DiamondSure Diamond Core Drill Bits, for use on glass,
stone and tile should be used at slow to very slow speeds, with
the speed decreasing as the hardness and abrasiveness of the
material increases. Also, since the circumference of a
bit increases as the bit diameter becomes larger, the drill rpm
speed must be reduced on larger bits to offset the increased
speed at which the outside cutting edge is moving.
The following table shows recommended
drill speeds for DiamondSure Diamond Drill Bits. Drill
speeds considerably in excess of these speeds will quickly burn
up the diamond bits. Reduced drill speeds, low drill pressure
and use of water for lubrication will extend drill bit life.
for DiamondSure Brand Diamond Drill Bits
Diamond Drill Bits
Drill Speed (rpm)
Glass, Ceramic & China
Limestone & Marble Stone
Ceramic Wall Tile
Porcelain Wall Tile
Porcelain Floor Tile
(Not for use on Concrete or Masonry,
or with Hammer Drills)
speeds, low drill pressure and increased use of water lubrication
will extend drill bit life considerably.
All materials vary in hardness
and abrasiveness and it is impossible to determine exact drill
speeds every application. 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.
The drill speed, pressure and lubrication must be balanced to
assure that the drill bit does not overheat. 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.
Drill Bit Lubrication
Water or coolant must always
be used to cool and lubricate the tip. The lubrication
reduces heat build-up, prolonging drill bit life and helps avoid
heat fractures in the material. Water is used most often
as the lubricant, since it works very well and has no cost.
Oil based lubricants do not work well with diamond drill bits
and should not be used.
Good lubrication is critical.
Minimal lubrication may keep the bit from burning up, but very
good lubrication techniques can extend bit life by a factor of
3 or even 5 times.
When drilling in fiberglass,
a diamond drill bit may be used dry or with a very small amount
of water. 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 too much pressure.
When drilling in hard, abrasive
materials such as limestone, sandstone, hard ceramic and porcelain
tiles, marble or granite, it is critical to have lots of lubrication.
With these hard materials, it is common to drill under water
or to have a small amount of water constantly running over the
drill bit and into the bore hole. In either case, the "pumping"
technique described below is needed to assure water reaches the
very tip of the bit.
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.
Note side tip
Using a clay dam
to drill glass
Using a pan
to drill a ceramic plate.
Tips & Techniques
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 basic clay dam lubrication method
(4 rating) should provide a drill bit life of approximately twice
that of using a squirt bottle (2 rating).
Squirt Bottle w/pumping action
Dam w/pumping action
Under Water w/pumping action
(1 poor - 10 good)
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 bit
tip, it is very important to use a "pumping" technique
described below. Without the pumping technique, the water
will not reach 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 can be 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 is also very important to
increase the lubrication at the tip. Without the pumping
technique, the water will not reach the very tip of the drill
bit. The clay can be used many times if it is stored in
a plastic zip-lock style bag to keep it from drying out.
For low volume repetitive work,
it is also possible to place the material into a pan or plastic
tub (place a thin plastic board underneath so you don't drill
into the pan) and fill the pan with water so that it covers the
surface of the material being drilled. The water should
cover the side lubrication hole on the tip of the diamond
drill bit. To allow lubrication to reach the drill tip,
it is very important to use a "pumping" technique
described below. Without the pumping technique, the water
will not reach the very tip of the drill bit even though the
bit is under water.
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 will not reach the very tip of the drill.
No matter what lubrication method
is used, a periodic "pumping" action will significantly
improve lubrication at the drill bit 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 15 to 20 seconds or so). This
assures that water enters the drill tip area completely and fully
lubricates the very tip. Pumping the drill improves
lubrication at the tip and will improve drill bit life considerably.
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. However, 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 to medium pressure
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 material breakage to occur.
Drill Head Pressure
for DiamondSure Diamond Drill Bits
Pressure (lbs.) *
6 to 8 lbs.
Glass, Ceramic & Porcelain
8 to 12 lbs.
Limestone & Marble Stone
12 to 18 lbs.
Ceramic/Porcelain Wall Tile
15 to 20 lbs.
Stone Style Porcelain Floor
18 to 30 lbs.
18 to 30 lbs.
Drill press arms leverage hand pressure by a
factor of about
6 to 8. So 2 lbs. of hand
pressure on the drill press arm will apply about 14 lbs of pressure
to the drill head.
If a diamond drill bit develops
yellow, brown, blue or black 'burn marks' around the tip, it
is an indication of extreme heat caused by the excessive drill
speed, too much pressure on the drill, or inadequate lubrication.
When 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.
Impact type "hammer drills"
should never be used with diamond drills as they have no benefit
and will cause the tip of the bit to mushroom or split.
Cutting Speed, with
Drill Speed, Pressure and
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 drill
bit life considerably.
of Pilot Bits on Diamond Drills
Pilot bits are often seen on
standard metal core drill bits or hole saws designed for use
on wood and other soft materials. A pilot bit is a small
drill bit located in the center of the hollow core drill bit,
that keeps the bit centered while starting a hole. Pilot
bits are especially convenient when using a core drill bit in
a hand drill. When a pilot bit is not present, a core drill
bit may tend to "walk" until it seats into a groove.
However, pilot bits are rarely
used on diamond drill bits since there are many drawbacks of
a pilot bit with the diamond core drill bit design and drilling
in very hard materials.
- A diamond pilot bit adds significant
cost to the already expensive diamond core drill bits.
- The diamond pilot bit often
wears out before the main core bit.
- Drilling times are considerable
when drilling in very hard materials and a pilot bit increases
the drilling time even more.
- A pilot bit eliminates the shaft
water-feed lubrication hole and does not allow the use of center
A template can easily be used
to start a core drill that does not have a pilot bit. This
simple technique is discussed in the following section.
made from plastic.
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
the 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.
Tempered Glass - Not Recommended
Tempered glass can be drilled,
however, breakage may run as high as 80% to 90% depending upon
the degree of temper in the glass.
do not recommend trying to drill tempered glass!
The manufacturing process of
making tempered glass results in the glass having a large amount
of stress between various portions of the glass. The stress
points might look much like a piece of wood containing lots of
"knots", however, there is no outward appearance to
indicate the hidden stress. Highly tempered glass will
often crack at the stress points near the hole. Since the
amount of hidden stress increases with the degree of temper,
the success rate of drilling tempered glass reduces with the
increase in glass temper.
There is no way to know the amount
of temper in a piece of tempered glass, so there is no way to
evaluate the amount of risk involved in trying to drill it.
Therefore, we DO NOT RECOMMEND attempting to drill tempered glass.
Bonded diamond core drill bits
are designed to drill to depths of about 1/2". We
do not recommend drilling in materials much beyond that depth.
However, it is often possible to push the bits beyond their design
limits by drilling to a depth of about 1/2", then removing
the core before drilling deeper. The core can usually be
removed easily on smaller holes by slipping a screwdriver down
the drill slot and twisting. On larger holes, you may need
to chip out the center core 'plug' with a chisel before continuing
to drill. Removing the core reduces friction and heat build-up
caused by the 'plug' or 'core' and will usually allow drilling
deeper holes if extremely good lubrication is used.
Drilling deep holes with a bonded
diamond drill bit is generally limited to about 1" in depth
depending upon the specific material being drilled. Even
when removing the core periodically and using very good drilling
techniques, the friction still increases considerably and limits
deep boring. For deeper holes, a 'sintered' diamond drill
bit is normally required. The more expensive sistered bits
have diamonds embedded directly into the metal tip and are most
appropriate for deep drilling.
through the material)
Most applications require a person
to drill completely through the material, however some applications
require drilling a 'blind' hole that does not go completely through
the material. Blind holes are simple with traditional drill
bits that drill out the complete hole. However, solid drill
bits are not practical when drilling in extremely hard materials
and solid diamond drill bits are rarely made.
A blind hole can be drilling
using a hole saw style drill bit by drilling partially through
the material and then removing the core or plug. The core
can usually be removed easily on smaller holes by slipping a
screwdriver down the drill slot and twisting. The core
will break off near the bottom of the hole and can be removed.
On larger holes, you may need to chip out the center core 'plug'
with a chisel and very large holes may require drilling several
smaller holes into the core to allow it to be chipped away and
Ceramic and Porcelain Tile
Ceramic and Porcelain tile, used
on walls, counters and floors, has changed considerably over
the years. Ceramic tile was first developed with a heat-hardened
vitrified glass finish on the top surface. The inside of
the Ceramic tile was still relatively soft. Since the tile
was easily scratched, manufacturers developed better manufacturing
techniques to make the surface finish much harder. The
newer Ceramic tile now has an extremely hard surface that wears
very well and the inside of the tile is also very hard.
Most porcelain tile that we have tested is now as hard as Granite
and some even approaches 'tool steel' in hardness. While
this is a distinct advantage from the stand point of wear, the
newer Ceramic tile is often difficult to drill without a diamond
Porcelain tile was originally
developed as an alternative to Ceramic tile, for use in floor
applications where usage and wear was more extreme. Porcelain
tile is made with various mixtures of materials, often including
feldspar and quartz, which are two of the major components of
natural Granite. The use of Porcelain floor tile was generally
limited to commercial applications, but by the late 1980's, Porcelain
tile use expanded more into residential construction.
In the 1990's, tile manufacturers
began to expand their Porcelain tile product lines to include
many different styles and many that closely resembled natural
stones. Because of the natural stone look, Porcelain tile
use on walls and counters became more popular. Finally,
in the late 1990's tile manufacturer's experimented with new
manufacturing techniques that made the Porcelain tile significantly
harder. As with Ceramic tile, this was a major advancement
resulting in reduced wear and very long life. However,
many Porcelain tiles are now as hard as Granite and some are
even harder. The newer type of high-quality, "super-hard",
"Class V" Porcelain tile is now almost impossible to
drill with the older "spear point" carbide drill bits
and generally can only be drilled with a diamond drill bit.
When drilling in the newer super-hard
tile, using a diamond drill bit is the only reasonable option.
However, even with a diamond drill bit, the drilling process
takes considerable time and the extremely hard material is not
very forgiving if inappropriate drilling techniques are used.
It is critical that good drilling techniques be used. Appropriate
drill speeds, low drill pressure and good lubrication are critical.
Drilled to insert lights.
Drilled to insert lights.
Using a clay dam
to drill glass
Purple LED lights with
with bubbles and swirls.
Frosted Wine Bottle
Drilled to insert lights.
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Glass Bottles - Drill Glass Block
Drilling in glass block or bottles
is basically no different than drilling in normal glass.
If you use the appropriate speed, use low drill pressure and
plenty of water for lubrication, you won't have any problems.
Glass breakage with carbide bits is fairly common, but with a
good diamond bit, it is extremely rare. There are a few
very important facts and tips that will helpful when drilling
glass block or bottles.
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 important characteristics to be aware
of. Glass block can vary significantly as to the thickness
of the glass wall and some glass block is tempered. 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 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. Some glass block and bottles are
tempered to increase the strength of the glass. Tempered
glass should be avoided if reasonably possible.
Experienced crafters who work
with glass block and bottles learn to search for different types
and styles to test. After drilling a sample of each, it
is obvious which has a thin wall and if any are tempered.
Also, crafters who are drilling lots of glass blocks or bottles,
normally develop some type of "clay dam" or pan drilling
method, so that it can be drilled under water to improve lubrication
and extend drill bit life. The "clay dam" method
of lubrication is very effective for drilling in glass block
and is simple to use. Under water pan drilling works best
for bottles. "Pumping" the drill bit is also
very important since even under water, the tip of the bit will
go dry after drilling about 1/8" deep. Water lubrication
techniques are discussed in more detail in the Lubrication
Tips & Tricks section.
Glass block normally has a vacuum
inside. Some of the water and glass dust will always be
sucked inside when the hole breaks through. However, it
is easy to rinse out the inside of the block with water as long
as the dirty water inside is not allowed to dry out. The
plug from the hole will sometimes be pulled into the block -
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 when nearing the
back of the glass to avoid splintering as the drill breaks through.
Some Additional Tips for Drilling
Glass Blocks & Bottles
A piece of wire from a regular
coat hanger or a small wooden dowel work 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.
The most popular diamond drill
bit for glass block drilling seems to be the 1/2" size since
it is about the right size for light strings. We prefer
a 5/8" sized bit because the slightly larger hole gives
a little extra room when inserting the lights or when pushing
them around and allows easy remove of the lights if you change
your mind or need to change a bulb.
Glass blocks sometimes have a
white or cream paint coating around the outside edge to give
better adhesion for building mortar or caulk. Most people
remove the paint, but some just hide it under a ribbon.
If the paint is hard to remove, soaking the block in hot water
usually softens the paint and allows easy removal with a common
kitchen dish scratcher.
Glass blocks come in many sizes,
shapes and surface textures. The ones with a heavy surface
textures tend to work best since they diffuse the light and hide
the light string wires better. Our research has shown that there
are at least 15 different surface textures available (there are
probably far more), so a little searching can result in finding
some unusual patterns that make very nice light blocks.
Most people seem to use the standard 8"x8"x3"
blocks, maybe because they are easily available. We have
found that the smaller 6"x6"x3" blocks and even
some of the odd shaped triangular, brick shaped and corner blocks
are are also especially nice because of their unique sizes and
shapes. There are no limits to the artistic possibilities,
so don't be afraid to try something different.
A hot glue gun with clear glue
works very well to attach ribbons and bows, or ribbons can be
tied as if you were wrapping a package. Most people
tend to start out with the multi-colored lights then quickly
learn that the white and single colored lights are also beautiful.
The non-multi colored lights are especially nice for light blocks
that can be used all year round. Light strings also come
with various colored wire, so experiment with the white lights
with white wire or the red lights with red wire, etc to see what
Finally, if you ever get a chance
to try the "LED" or "Tiny Lights", give them
a try - especially the big strings of 60 to 100 (it takes a few
more lights because they are so small). Yes, they cost
more, but they create almost no heat and bulbs last nearly forever.
Some LED light strings have a
light function controller that gives a special random
blinking pattern that blinks, twinkles and strobes, etc.
If you can find the type with the light controller, the LED strings
with the special lighting affect is well worth the additional
cost. Our experience is that most people who try the LED
lights with the controllers rarely go back to the standard bulb
In drilled glass
Aquariums are often drilled to
allow for installation of side-entry filter systems rather that
standard top-mount systems. The side-entry systems also
provide better flow-through water movement where that is a special
factor. Drilling in aquariums is not difficult - it is
basically the same as drilling normal glass. However, additional
precaution should be taken when drilling aquariums compared to
There is always a small risk
of causing a break when drilling any glass. While the risk
is extremely small if proper drilling techniques are used, this
small risk is always there. If a break would occur when
drilling in regular glass, it is frustrating, but not a major
loss. However, the loss of an aquarium is much more significant,
so reasonable care should be taken.
As additional 'comfort', we offer
that the structural integrity of glass increases significantly
as it becomes thicker. So, the small risk of a drilling
problem actually reduces significantly as the size (and cost)
of the aquarium increases. Based upon our testing and our
customer contact, we offer the following suggestions for aquarium
Take proper care: You don't need to be an expert
at drilling glass or aquariums. No matter if it is a 20
gallon tank or 2,000 gallons. Take your time, use proper
drilling speeds, low drill pressure, good water lubrication and
follow a few basic cautions relative to aquarium drilling.
Be sure you have the right
sized drill bit:
Pipe is measured as an inside diameter. So 1-1/2"
pipe or a 1-1/2" fitting will have an 'inside diameter'
of 1-1/2". However, the outside diameter can vary
depending upon the type of pipe or fitting used and depending
upon the specific manufacturer. Be sure to measure the
outside diameter properly so that you drill the correct size
hole. This may sound rather basic, but we assure you that
it is a common mistake.
Avoid drilling in the bottom
of the tank: The
bottom of a tank is often tempered glass, but it is extremely
rare for the sides to be tempered. Additionally, the water
weight on the bottom is significantly higher than on the sides
of a tank. Anytime glass is cut or drilled, micro fractures
always occur along the cut, plus a hole reduces the structural
strength of the glass. While tanks are generally "over
engineered" to be much stronger than actually needed for
their capacity, the bottom is the "weakest link" and
should generally be avoided.
Drill at least 1" from
the sides of the glass:
All glass contains minor imperfections and flaws. Micro
fractures also occur along the edge of glass when it is cut.
To avoid placing any additional stress on those weak spots, we
recommend staying at least 1" away from any glass edge.
Use proper lubrication techniques: Basic lubrication techniques are
discussed above in Diamond
Drill Bit Lubrication Tips & Techniques. The best
lubrication method for tank drilling is to position the surface
horizontally and use a dam made of clay or similar material around
the drill area. The method as discussed in the above section,
is very simple and also very effective. If a large stationary
tank is being drilled in the vertical position, use the 'spray
method' and take care to get as much of the spray into the drill
slot as possible.
Assure adequate lubrication: While drilling, it helps to raise
the drill up and down a fraction of an inch once in a while as
you drill (about every minute or so). This merely assures
that water enters the drill hole completely and fully lubricates
the very tip of the bit . The technique is especially helpful
when drilling larger tanks with thick walls.
Ease off when you are nearly
through: As a drill
breaks through the back side of any material, it will cause some
splintering. Due to the brittle fragile nature of glass
and your desire to retain structural integrity, you want to minimize
the splintering. Merely reduce the drill pressure as you
near the back of the glass. This is one of those rare instances
where time is your friend. If it takes you 3 minutes to
drill 3/4 of the way through, back off and use another 3 minutes
to go most of the the the remaining 1/4. The final 1/32"
to 1/16" is the most delicate, so again take your time and
ease up on the pressure.
If your hole ends up being
a little too tight:
You don't want the hole to be any larger than you actually need,
but sometimes people cut it a little too close. Since the
pipe fittings are normally plastic, an easy solution is to use
fine sand paper to reduce the outside diameter of the fitting
slightly. If your hole is a little too large, the gasket
on the fitting normally provides extra room and should provide
an adequate seal.
Drilling holes in any glass reduces the structural integrity
of the glass and will reduce the safety levels that were intentionally
engineered into an aquarium. We must specifically state
that in offering these tips and techniques, we do not accept
any liability and disclaim any express or implied warranties
and all incidental or consequential damages should problems arise
from using our products for drilling aquariums.
Drill Bit Life
The life span of all types of
drill bits is affected by the hardness and abrasiveness of the
material being drilled, the thickness of the material, plus the
speed of the power drill, the amount of pressure used and the
use of adequate lubrication. The hardness and abrasiveness
of materials can vary significantly. Even materials which
appear similar have varying degrees of hardness and abrasiveness.
Each individual's drill speed, pressure and amount of lubrication
also varies significantly. As a result it is nearly impossible
to estimate the life of a diamond bit.
For example: On standard
1/8" glass, an electroplated diamond bit under 3/4"
may last for 200 to 300 holes, or more, depending upon the specific
glass and specific drilling techniques used. Larger bits
tend to run about half as long due to a slightly different type
of cutting action. Drilling in 1/4" glass, being twice
as thick, will normally produce only half as many holes over
a drill bit's life, if the glass hardness and drilling techniques
are the same. Tempered glass has differing degrees of temper,
and will reduce drill bit life by 75% to more than 90%, compared
to standard glass.
Lubrication has a significant
affect upon drill bit life. Using a center water feel lubrication
device or drilling under water with the water level above the
side tip lubrication hole gives the best lubrication and the
best drill bit life. Using a clay type "dam"
gives fairly good lubrication but since the water normally does
not reach the side tip lubrication hole, the lubrication inside
of the bit is much more limited. As a result, using a dam lubrication
method will often reduce drill bit life by 25% to 40%.
Finally, spraying or splashing water onto the bit for lubrication
works, but lubrication is very limited and drill bit life can
easily be reduced by 40% to 60% compared to using a good water
On the extremely hard and abrasive
materials, such as granite or the newer "super-hard"
porcelain floor tiles, a bonded diamond drill bit may only produce
10 to 15 holes in 3/8" material. However, the same
drill bit may produce as many as 30 or more holes, all depending
upon the specific material and thickness and the especially the
specific drilling techniques used. Tests on some of the
less hard, class III floor tiles have ranged from 40 to 60 holes,
or more, and in standard 1/8" window glass, drilling tests
have resulted in hundreds of holes.
These examples are are all based
upon extensive testing in different materials using proper drill
speeds, drill head pressure, and lubrication. Test results
were much less, using poor drilling techniques, and extreme tests
using improper drilling techniques often resulted in a bit "burning
up" after only one or two holes.
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