During the last decade concrete and construction industry has experienced sharp increases in labor rates, equipment costs, and overhead expenses. These increased costs had made the cost of diamond core bits used in drilling applications, a relatively minor factor in the overall cost equation. Given the high labor and overhead costs involved in most drilling operations, the speed with which the job is done is becoming ever most important. Today, in order to remain completive, the drilling operator must be able to accurately estimate amount of time, money, and resources a job will require. Unfortunately, today many drill operators waste valuable time and money. By using outdated drilling techniques and drilling equipment, that heavily relies on guessing and operator trial and error.
an effort to help our customers provide more accurate system of
estimating and predicting diamond drilling costs. As well as estimating
time required to finish job and predicting diamond core bit performance
on specific material type. Several studies were conducted, revealing
valuable solutions that you can start using today! Some of the
variables evaluated in these studies include: applying different amounts
of pressure to the diamond core bit, using higher horsepower hydraulic
drilling equipment. As well as increasing the diamond core bit RPMs
(speed). By understanding these variables and how they work
together, you will be able to increase
the speed of which diamond core bit drills (penetrates) through material
being drilled. Hence reducing amount of time spend on drilling.
New diamond core bit designs and segment matrix bond compositions have been designed to help increase drilling speed, without sacrificing diamond core bit life. Despite improvements in diamond core bit manufacturing technology, optimal balance of horse power and drilling force applied must still be achieved in order to obtain right combination of drilling sped and diamond bit life.
drilling horsepower is a function of both diameter of diamond bit and
well as the type of concrete or allied material being drilled.
To illustrate the interdependence of these two variables, several tests
were conducted with three different diamond bit sizes to determine their
optimum parameters. Using both reinforced and non reinforced concrete
material. Special care was used to replicate true field drilling
conditions in all aspects, from equipment used to typical procedures
AND NON-REINFORCE CONCRETE
types of concrete are commonly encountered in construction and highway
drilling applications. Both materials require different drilling
conditions and produce different drilling results. Drilling through a
steel bar produces a different type of strain on the diamond bit and
hence a different wear on the diamond bit cutting surface.
Drilling process on plain concrete however is quiet different. Non-Reinforced Concrete material is removed by means of crack propagation. The diamond in the diamond bit produces stress on relatively brittle concrete which causes cracks to be generated. These cracks result in pieces of
being broken away from the base material which allows the diamond bit to
penetrate the material being drilled. This can usually be seen by the
drilling swarf collected during the drilling of non reinforced concrete.
Concrete chips are very rough and irregular in shape, indicated a
action is reinforced concrete is quiet different. Most users find it
more difficult, takes longer, and cost more to drill reinforced concrete
than any other concrete or allied material. In Reinforced Concrete, the
steel bar is cut by diamond crystals n a machining mode rather
than by fracturing. You can usually see drilling swarf that contains
particles of steel that are shaped like curls. Drilling reinforced
concrete puts a very high strain of diamond core bit cutting surface.
When drilling through the reinforced bar, the drilling surface of the
diamond bit encounters a very tough and relatively ductile material.
However as the diamond bit rotates the same section of cutting surface
encounters the relatively brittle concrete. This causes
loading and unloading of diamond bond material and diamond
core bit life and drilling speed is considerably reduced when drilling
this material. On many applications diamond core bit life can be reduced
by as much as 50% depending on steel amount and depth in concrete.
a diamond core bit reaches and hits steel, you will often notice sparks
coming from the drilling zone. This is an indicator that you have hit
reinforced steel. The operator should reduce drilling speed and decrease
the diamond bit is rotating at 500RPM each segment of diamond core bit
penetrates rebar 1000 times per minute or 17 times per second. Resulting
in more rapid breakdown of diamond bond matrix. What follows is
increased diamond pullouts and possible premature fracture of diamond in
OPTIMAL DRILLING SPEED (FEED RATE / PENETRATION RATE) AND DRILLING RATIO
In order to determine most optimal feed rate (penetration) and drilling ration, several tests were structured using 3 different diameter diamond core bits. Horsepower of drilling machine was increased from 1.5 to 5 H.P. and 2 diameter diamond bit showed sharp increase in penetration rate and equally rapid decrease in drilling ratio. Thin wall diamond core bit was used in the first test.
Its relatively small surface area
of 0.81 sq in resulted in a very high unit pressure (PSI) on drilling
surface. Hence the concrete material was removed rapidly. The sight
affects was fast wearing of the diamond core bit section. This was
specially true at higher horsepower levels on reinforced concrete. The
steel bar accelerated the wear on the bit because the increase stress on
the bond matrix and diamond crystals. The rebar also caused a
reduction in the penetration rate (drilling speed) due to the difficulty
in drill the steel.
For the 4 diameter diamond bit, increasing horsepower from 1.5 HP to 7 H produced significantly increase in penetration rate with only gradual decrease in drilling ratio. The decrease in drilling ratio was much slower than what occurred for 2 diameter bit because the larger surface area of the 4 diameter diamond bit distributed the thrust over a wider area. The penetration rate in non reinforced
continued to increase even at highest horsepower used in test 7 HP.
However in reinforced concrete drilling ratio dropped rapidly as
horsepower was increased. Similarly penetration rate reached a plateau
at about 4 HP. Using power above this level in reinforced concrete
produced only minor increases in Penetration Rate.
the 6 diameter diamond bit, the penetration rate continued to
increase as horsepower was increased in both the reinforced and non
reinforced concrete. The large cutting surface area of the 6 diamond
concrete bit cause the bit thrust to be more widely distributed. Hence
producing lower unit pressure on drilling surface. In non reinforced
concrete, penetration rate continued to increase at highest power used 7
HP, with only gradual decrease in drilling ration. In reinforced
concrete, 6 diamond concrete bit reached a penetration rate plateau
at approximately 6 HP.
CONCRETE DRILLING COST EQUATION
in horsepower and diamond core bit feed rates results in a different
combination of diamond core bit life. (Drilling Ratio) and sped of
drilling (Feed Rate or Penetration Rate). There is an ideal
horsepower of each diamond core bit and material combination. The
ideal horsepower would be at the point where the sum of the costs
associated with diamond core bit life and operating costs are at the
In order to determine the optimum horsepower for the three different size diamond core bits used in this experiment, an equation was derived to determine drilling cost rate as a function of Penetration Rate (PR) and Drilling Ration (DR).
= Diamond Core Bit Cost + Operation Cost
Diamond Core bit cost = (Distance Drilled x Diamond Core Bit Price)
(DR x Segment Height
Operating Cost = (OCR x Distance Drilled)
Drilling Cost = (Diamond Core Bit Price + OCR)
Distance Drilled (DR x Segment Height PR)
= Number of inches
Diamond Core bit Price
= Initial cost of
diamond core bit
= Drilling Ration (inches drilled per thousands inch of diamond core bit wear)
= Total available
segment height expressed in thousands of an inch
Operating cost Rate
Cost of labor, overhead, and equipment expressed in dollars per
PR = Penetration Rate
expressed in inches per minute
will use the equation to determine the cost of drilling for the three
different diamond core bit sizes tested in this experiment for both
reinforced and non reinforced concrete
Drilled = 100 inches
core Bit Price = 2 diameter ($200.00), 4 diameter ($325.00), 6
Height = 0.3 inches
Cost Rate = $25.00 per hour
As you can see there is an optimum horsepower for each combination of diamond core bit diameter and material. Optimum horsepower can be determined where sum of the Diamond core Bit cost and Operating Cost are at a minimum. Conditions used in this experiment resulted in the following optimum drilling horsepower
Non Reinforced Concrete Reinforced Concrete
2 diameter 3.5 HP 1.5 HP
4 diameter 5.0 HP 3.0 HP
levels above were determined assuming standard Operating cost of $25.00
As this experiment shows the optimum horsepower level for reinforced concrete is lower than for non reinforced concrete
as much as possible about the material to be drilled and relaying this
information to diamond core bit manufacturer is important to obtain the right
diamond core bit for your application. Before we can recommend the
right diamond core bit for your application, knowing what type of aggregate
that is to be drilled as well as whether reinforcing steel will be present and
maximum drilling depth. Some concrete and allied materials are harder than
others. Hence more difficult and longer to drill. For example: Limestone, slag
and coral aggregate are relatively soft and abrasive materials. These are
easily drilled with very fast drilled speed. On other hand concrete with river
gravel or quartzite is of medium difficult to drill. Flint or granite
aggregate is generally considered among the most difficult to drill.
size of aggregate can also play a factor in overall drilling performance of
diamond core bit. Concrete aggregate are frequently in range of ½ to 2.
Concrete made with 2 flint aggregate will be extremely difficult to drill,
but concrete with ½ fling aggregate is drilled much more easily.
addition to the aggregate the type of sand used to make the concrete can
influence the selection of diamond core bit. Many natural sands are quartzitic
and have been rolled by water for many years and are smooth and dull.
Similarly, manufactured sand usually has sharp and abrasive edges that can
wear a diamond core bit bond very quickly.
concrete made with hard aggregates also requires more power. If there
is not enough power, diamond core bit speed should be reduced.
DRILLING REINFORCED CONCRETE
reinforced concrete is more difficult, takes longer, and costs more than
almost any other concrete and allied material. Diamond core bit life and
drilling speed is considerably reduced when drilling this material. On many
applications diamond core bit life can be reduced by as much as 50% depending
on steel amount and depth in concrete.
a diamond core bit reaches and hits steel, you will often notice sparks coming
from the drilling zone. This is an indicator that you have hit reinforced
steel. The operator should reduce drilling speed and decrease coolant flow.
operating speeds for drilling concrete are around 10,000 surface feet per
minute. It is important for the operator to maintain appropriate operating
conditions to maximize diamond core bit life, drilling speed and overall
performance. Actual drilling speed will usually have to be adjusted to
accommodate the aggregate type and amount of steel encountered in concrete
being drilled. Usually higher drilling speeds make the diamond core bit act
harder and often lengthen diamond core bit life. The trade off is slower
drilling speed. Decreasing diamond core bit speed will make the diamond bit
act softer, but diamond core bit life will also decrease.
you are not sure about the correct or optimal drilling sped to use for
particular material/application, it is better to error on side of lower
drilling speed rather than higher speed. Start in the lower RPM range, and
once the diamond core bit is working well, increase the speed to optimize
drilling life. When drilling softer abrasive materials, a faster drilling
speed and forward traverse rate and more coolant should be used.
Machine Drive Power
of power available to diamond core bit being used is also another important
variable to consider in optimizing your concrete diamond drilling application.
Drilling Machine will less power than required can result in diamond core bits
that will glaze over, resulting in slow drilling speeds.
machine power requirements for typical concrete drilling operations is 2 to 20
horsepower. In order for diamond core bit manufacturer to provide best diamond
bit for your application, it is important to know the maximum horsepower of
the drilling machine used. Frequently diamond core bits with soft bond
segments will wear faster if used with high horsepower drilling machines.
However this is not always the case, and there are numerous exceptions to this
Diamond core bits made with segments of hard bond will work better on higher horsepower drilling equipment. Diamond core bits require that right amount of pressure be applied for optimal drilling results. In order to maintain constantly sharp diamond crystals, sufficient amount of pressure should be applied for the material being drilled. If too little pressure is applied, diamond crystals will become dull and diamond bit stop drilling or drill very slowly. At same time operator must be careful to not over do it, because too much pressure can damage the diamond core bit.
& ALLIED DRILLING MATERIALS
length of curing time after concrete is poured greatly affects the way a
diamond core bit will interact with it during drilling. Curing can be affected
by weather (temperature, moisture and time of year) and the composition
(admixtures, aggregate and sand).
is typically in its green state for 6 to 48 hours after it is poured. In this
early state, the sand has not completely bonded with the mortar and the
concrete has not reached full hardness. When cutting green concrete, the sand
loosens more readily, flows more freely in the slurry, and produces much more
abrasion on a diamond blade.
concrete has typically set at least 48 hours. The sand has completely bonded
with the mortar and the concrete has reached full hardness.
the size and type of aggregate have a great impact on the overall hardness of
concrete. The aggregate can make up as much as 75% of the total volume. As a
general rule, larger aggregate tends to make the concrete act harder, slowing
drilling process. Smaller aggregate makes the concrete act softer, allowing
for faster drilling. Large aggregate can average up to 11/2
in diameter, while smaller aggregate can average in the range of 3/8
in diameter. The type of stone used as aggregate also has a great impact on
the hardness of concrete. The following chart shows the types of minerals
often used for aggregate and their relative hardness.
amount of rebar reinforcing on concrete is also a critical factor in
determining material hardness. The more rebar the harder the concrete
is always considered soft and abrasive. It does not cure and does not come in
the range of hardness that concrete does. Even though asphalt includes
aggregate, the size is consistently small and the type of aggregate has little
bearing on the cutting quality. Shortly after it is rolled, asphalt is ready
to be cut. The extremely abrasive nature of asphalt makes undercut protection
on a diamond blade essential.
block tends to consistently have soft, abrasive qualities while brick tends to
be hard and
less abrasive. There are a large variety of brick types on the market, each designed and manufactured to provide certain qualities. The degree of hardness is mostly determined by the clay mixture, method of manufacture and the firing temperature. Generally, brick and block are softer and more abrasive than ceramic tile and stone.
What you should know before you buy your next diamond drill?
UKAM Industrial Superhard Tools Division of LEL Diamond Tools International, Inc.
28231 Avenue Crocker, Unit 80 Valencia, CA 91355 Phone: (661) 257-2288 Fax: (661) 257-3833
Diamond Drills Home Page
Diamond Core Drills - Diamond Core Bits - Thin Wall Core Drills - Thin Wall Core Bits - Specialty Drills - Metal Bond Core Drills - Electroplated Core Drills - Small Diamond Drills - Drill Bits - Water Swivel Adapters - Custom Core Drills
About Us - SMART CUT technology - Contact Us - Visit Us
Diamond Drill/Bit Support
Selecting Right Diamond Drill - Drilling Recommendations - Diamond Drill Guide - Trouble Shooting - Getting Results with Diamond Tools
Purchase Diamond Drill/Bits Online
Browse Diamond Drills/Bits & Purchase Online - Special Offers
Find a Distributor - Become a Distributor - Current Distributors - Become an Affiliate