|
Call us today:
1-800-233-8655
- or -
(651) 487-1880
|
What is a Diamond Blade?
A diamond Blade is a circular steel disc with a diamond bearing edge. The edge of the blade may be smooth,
or textured, continuous rim, or a segmented rim with smaller, individual sections.
The blade core is a precision-made steel disc, which may have a continuous rim, or a slotted rim.
The slots (also called "gullets") provide faster cooling by allowing water or air to flow between the segments.
The slots also allow the blade to flex under cutting pressure.
Most blade cores are tensioned at the factory, so the blade will run straight at cutting speeds. Proper tension
also allows the blade to remain flexible enough to bend slightly under cutting pressure and "snap" back into position.
Diamond segments or rims are made up of a mixture of diamonds and metal powders. Diamond used in blades
is almost exclusively manufactured diamond in various grit sizes and quality grades. In the manufacturing process,
the metal powder and diamond grit mixture is melted at high temperatures to form a solid metal allow (called the bond
or matrix) in which the diamond grit is suspended.
The segment or rim is slightly wider than the blade core. This side clearance allows the cutting edge to
penetrate through the material.
To attach the diamond rim or segments securely to the steel core, several different processes are used.
1) Brazing - Silver solder is placed between the segment or rim and the core. At high temperatures, the solder
melts and bonds the two parts together, 2) Lazer welding - The diamond segment and steel blade core are welded (fused)
together by a laser beam, 3) Mechanical bond - A notched, serrated or textured blade core may by used to "lock" the diamond rim or segments
onto the edge of the blade. Mechanical bonds usually also include brazing or other metallurgical bonding processes
to hold the rim or segments in place.
* This information applies to diamond blades, diamond bits and other diamond grinding wheels
How Do Diamond Blades Work?
Diamond blades don't really "cut" like a knife… they grind.
During the manufacturing "break-in" (grinding) process, individual diamond crystals are exposed on the outside
edge and sides of the diamond segments or rim. These exposed surface diamonds do the grinding work. The metal
"matrix" locks each diamond in place. Trailing behind each exposed diamond is a "bond tail" (also called "comet
tail"), which helps support the diamond.
While the blade rotates on the arbor shaft of the saw, the operator pushes the blade into the material. The blade
begins to cut through the material, while the material begins wearing away the blade.
Exposed, surface diamonds score the material, grinding it into a fine powder. Embedded diamonds remain beneath
the surface.
Exposed diamonds crack or fracture as they cut, breaking down into even smaller pieces. Hard, dense materials
cause the diamonds to fracture even faster. The material also begins to wear away the metal matrix through
abrasion. Highly abrasive materials will cause the matrix to wear faster.
This continuous grinding and wearing process continues until the blade is "worn out". Sometimes, a small
unusable part of the segments or rim may remain. It is important to understand that the diamond blade and the
material must work together (or interact) for the blade to cut effectively.
In order for a diamond blade to work properly, the diamond type, quality and grit size must be suited for the
saw and the material. The metal matrix must also be "matched" to the material.
Blades for cutting hard, dense (less abrasive) materials (such as tile, hard brick, stone or hard-cured concrete)
require a softer metal matrix. The softer metal matrix wears faster, replacing worn-out diamonds fast enough for
the blade to keep cutting.
Blades for cutting soft, abrasive materials (such as block, green concrete or asphalt) must have a hard metal
matrix to resist abrasion and "hold" the diamonds longer.
Water Cooled
Wet cutting diamond blades must be used with water to prevent excessive heat build-up during cutting. Using water on
the blade also reduces dust and helps remove cuttings.
A continuous water flow is critical. Using "wet" blades without water, even for a few seconds, causes excessive heat
and blade damage, and creates a safety hazard. Check the saw or tool carefully before using a wet cutting diamond blade.
Make sure it is safe to use the saw or tool with water.
Air Cooled
Dry-cutting diamond blades may be used dry, eliminating the need for water tanks, water hoses, or wet slurry cleanup.
These blades depend on airflow around the blade to prevent excessive heat buildup during cutting.
Use dry diamond blades for "intermittent" sawing. After every 10 to 15 seconds of cutting, take pressure
off the blade and allow it to run back up to full speed for several seconds. This "cooling" interval allows
air to flow around the blade, and dissipate the heat. Use dry diamond blades only for shallow cutting (1-2"
deep) or step cutting (making several shallow passes to reach the full depth required).
Target Dry Disc dry-cutting diamond blades are also designed to cut equally well wet, if the job or equipment permits.
Diamond Blade Performance
Blade performance is a combination of both cutting speed and blade life. Selecting the right blade (for the saw,
the material and the Job) is the most important factor in getting maximum performance. Many other variables
also affect blade performance. Changing any one variable will have an effect on cutting speed and blade life.
Here are some examples.
Exhibit A
Cutting Speeds and Depths
Diamond Blade Operating Speeds
Exhibit B
*Based on 9,500 SFPM (Surface Feet Per Minute) - the general optimum performance range for cutting concrete
and masonry products, + or - 10%.
For hard, dense materials such as stone and tile, the optimum performance speed is 10 - 25% less than the
speeds shown above.
Blade shaft speeds (RPM's at no load) for most tools will be higher than the recommended operating speeds shown
above. Under normal sawing conditions, the actual blade shaft speed of the tool will slow down under load,
and should fall within the optimum speed range.
**This speed (RPM) represents the maximum safe speed (in revolutions per minute (RPM)) at which each blade
can be used. Before using any blade, make sure the blade shaft (arbor) speed of the tool is within the "maximum
safe" limit of that blade.
Maximum Blade Cutting Depths
Exhibit C
Note: Diamond blade cutting depths listed above are approximate. Actual cutting depth will vary with the exact
blade diameter or saw type (or brand), or the exact diameter of the blade flanges. Cutting depth will also be
reduced if saw components (motor housing, blade guard, etc.) extend below the blade flanges.
Diamond Blade Performance - Concrete Cutting
Factors Involving Concrete
When cutting concrete, several factors influence your choice of diamond blades. These include compressive
strength, hardness of the aggregate, size of the aggregate, type of sand, steel reinforcing (rebar), and
green or cured concrete.
The guidelines in this section are for general reference only. Your best source for information
on the characteristics of the concrete you have to cut is from the original contractor. Contact your local
Department of Transportation or City Hall for help in tracking down this information.
Compressive Strength
Concrete slabs may vary greatly in compressive strength, measured in pounds per square inch (PSI).
| Concrete Hardness | PSI |
| Critically Hard | 8,000 or more |
| Hard | 6 - 8,000 |
| Medium | 4 - 6,000 |
| Soft | 3,000 or less |
Most concrete roads are 4 - 6,000 PSI, while typical patios or sidewalks are about 3,000 PSI.
Hardness of the Aggregate
There are many different types of rock used as aggregate. Hardness often varies even within the same
classification of rock. For example, granite varies in hardness and friability.
The Mohs scale is frequently used to measure hardness. Values of hardness are assigned from one to ten.
A substance with a higher Mohs number scratches a substance with a lower number - higher Mohs scale numbers
indicate harder materials. The scale below shows how some common minerals fall into the Mohs scale range.
Most aggregates fall into the 2 to 9 range on the Mohs scale. Some commonly used aggregates measure this way
on the Mohs scale:
Aggregate hardness is one important factor when cutting concrete. Because hard aggregate dulls diamond grit
more quickly, segment bonds generally need to be softer when cutting hard aggregate. This allows the segment
to wear normally and bring new, sharp diamond grit to the surface. Softer aggregate will not dull diamond
grit as quickly, so harder segment bonds are needed to hold the diamonds in place long enough to use their
full potential.
Size of the Aggregate
The size of aggregate affects diamond blade performance. Large aggregates tend to make a blade cut slower.
Smaller aggregates tend to make a blade cut faster. The most common standard sizes of aggregate are:
Pea Gravel … Variable in size, usually 3/8" or less diameter
¾" … Sieved size
1 ½" … Sieved size
Type of Sand
Sand is part of the aggregate mix, and determines the abrasiveness of concrete. "Small aggregate" is usually
sand. Sand can either be sharp (abrasive) or round (non-abrasive). To determine the sharpness of sand,
you need to know where the sand is from. Crushed sand and bank sand are usually sharp; river sand is usually round.
Green concrete is more abrasive than cured concrete. This is because when the concrete is not fully cured
sand can more easily be scraped off the surface being cut. More loose sand means more abrasiveness.
Amount of Steel Reinforcing (Rebar)
Heavy steel reinforcing tends to make a blade cut slower. Less reinforcing tends to make a blade cut faster.
"Light" to "heavy" rebar is a very subjective term. Examples include:
| "Light" | Wire mesh, single mat |
| "Medium" | #4 rebar, every 12" on center each way (OCEW), single mat wire mesh, multi mat |
| "Heavy" | #5 rebar, 12" OCEW, single mat #4 rebar, 12" OCEW, double mat |
"Heavy" rebar can also result from different grades of steel. Typical rebar is grade 40 steel. Grade 60
steel would make the example of #4 "medium" rebar above into a "heavy" rebar. Rebar gauges are in eighths
of an inch - #4 rebar is ½" diameter, #5 is 5/8". Where rebar specifications do not exist on a road, pull
a core sample before buying a blade.
Green or Cured Concrete
The drying or curing time of concrete greatly affects how the material will interact with a diamond blade.
Green concrete is freshly poured concrete that has set up but not yet fully cured. It is softer and more
abrasive than cured concrete. You need a harder bonded blade with undercut protectors to cut green concrete.
You need a softer bonded blade to cut the same concrete in a cured state.
Typically, concrete defined as "green" is six hours from pour or younger, but this can vary widely. Weather,
temperature, moisture in the aggregate, time of year and the amount of water in the mix all influence curing
time. Also, much concrete now has additives, which can either shorten or extend curing time. Consult your
mix design to find the relative curing time for your job. As soon as wet concrete sets up and does not
spall or ravel, green cutting can begin.
|
© 2006 - Esch Construction Supply, Inc.
|