The right diamond blade can mean the difference between an efficient, cost-effective and profitable job or one with additional costs and downtime. Knowing how to select the right blade for the right machine that is designed to cut the right material can save construction business owners time and money and increase profits. Owners should ask themselves five basic questions when choosing the right blade for a project and use this knowledge to correctly bid on projects as well as minimize the chances of troubleshooting blade issues.
1. Which materials are you cutting?
Correctly identifying the material to be cut directly affects the cutting speed and the life of the blade. Most blades are designed to cut a range of materials, which is limited by the hardness of the bond and the diamond quality used. However, for maximum performance, the blade should be matched as closely as possible to the material it will cut.
When cutting concrete, asphalt or green concrete, it is important to know what makes up the material. Knowing the type of aggregate within the slab is your best bet at finding a blade optimally suited to cut it. You can determine what is in the slab by observing and looking to see what aggregate is used, or by using a Mohs test. A Mohs test helps identify the hardness of the aggregate, which can help determine what type of aggregate you are up against. Most diamond blade manufacturers will specify which of their blades either cuts a particular type of aggregate (flint, river rock, limestone or abrasive sand, for example) or will list aggregate categories (hard, medium or soft). These aggregate and material charts will help narrow your blade selection to only the blades that will cut that particular type of aggregate.
2. What type of equipment are you using?
Knowing if you will be using a 5-hp power cutter or a 70-hp flat saw will impact blade choice dramatically. The size of the blade acceptable to use on the saw, the ability to use a wet or dry blade and the rpms needed to spin the blade all depend on the equipment.
- Blade size—Blades are engineered to be used on specific equipment. It is critical to select a blade that can be run on the equipment you plan on using.
- Wet or dry blades—Most equipment will have the ability to use water, but there may be a time when water can’t be used or isn’t available.
- RPMs—If a blade is run too fast or too slow, the blade will not work effectively and a loss of tension or excessive wear on the blade could result. Blades should list a maximum safe speed in revolutions per minute at which a blade can be used. Before using any blade, make sure the blade shaft (arbor) speed or the tool is within the “maximum safe” limit of that blade.
3. How deep are you cutting?
Knowing how deep you need to cut on a particular job will help you select the right blade diameter. Maximum cutting depths listed on blade packaging may vary from what it actually cuts in the field. Actual cutting depth will vary with the exact blade diameter or saw type or the exact diameter of the blade collars (flanges). Cutting depth will also be reduced if saw components (motor housing and blade guard) extend below the blade collars.
4. Are you cutting dry or wet?
Knowing whether or not you will have or need a water source on a job is important when selecting a diamond blade. Blades designed to cut dry can also cut equally well wet, but wet cutting blades absolutely must be used with water.
Dry-cutting diamond blades should be used only for shallow cutting (1- to 2-inch deep) or step cutting (making several shallow passes to reach the full depth required). Dry blades depend on airflow around them to prevent excessive heat buildup during cutting.
They are a good choice for “intermittent” sawing. Wet-cutting diamond blades must be used with water to prevent excessive heat build-up during cutting. Using water on the blade also reduces hazardous dust. Continuous water flow on wet-cutting blades is critical. Using a wet blade 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 to make sure it is safe to use with water.
5. Do you want more life or speed?
Which is more important: the initial price of the blade or the cost per cut? It may be more cost effective to purchase a low-priced blade for a smaller job or occasional use. For larger jobs or more regular use, a higher priced blade will actually be less expensive to use because it will deliver the lowest cost per cut. For extremely large jobs, the lowest possible sawing cost (cost per foot) is usually much more important than the initial price. Manufacturers will list performance/quality levels on blades so it is easy to select the blade with either more life or more speed.
Answering these simple questions to select the right blade will save a lot of time, money and headaches in the field. To learn more about troubleshooting blade issues in the field, see the Equipment Maintenance article in the November 2015 issue of Construction Business Owner or click here for the digital article.