For any fabrication shop, sawing is one of the most critical processes. However, a lot of questions arise from the process. Here are some common questions I have received along with some answers and suggestions for your sawing problems:
Q. Fred, We just bought a brand-new saw and we are having problems with blowout when we cut limestone or marble. It seems to work fine with granite. We are not sure if it’s the blade or the speed we are cutting? Do you have any advice?
A. Blowouts can be caused for many different reasons. Here are a few things I would check:
1. The Blade. Many of today’s blades are designed for granite and engineered stone. They are segmented and designed to cut through hard stone. Limestone and marble are softer and require a different blade altogether. A continuous rim blade is usually recommended.
2. Blade Diameter. The diameter of the blade is very important and has a direct effect on the surface feet per minute. Let me explain further. Marble, limestone and granite all have optimal cutting speeds. Most saws operate at fixed rpm. Unless you can adjust the rpm, the only way to change the rate of your cut (sfpm) is to change the blade diameter. You can ask the manufacturer for the proper size or you can calculate it yourself as follows:
Optimal cutting is determined by calculating the sfpm. To calculate this factor, you need to know the rpm and diameter of the blade, as well as the numeric value for Pi (3.14). The following is your calculation: sfpm = Pi x rpm x Blade Diameter. Here are the recommended sfpm by material: marble 6,000 to 8,000, granite 4,500 to 6,500 and limestone 7,500 to 10,000.
3. Glazed Blade. Blades over time can become glazed. They can be unglazed by running the blade through a brick or concrete block or you can purchase a dressing stone. This is especially true if you have a wood table. If you do cut through wood, you might want to laminate some masonry board to it. This way the blade will stay unglazed.
4. Speed of Cut. (Not to be confused with sfpm). This is your forward speed or how fast you’re moving the saw through the material. If you move too fast, it can cause blowout. Slow your speed down and see if this helps with blowout. There are many other reasons but these are the most common reasons for blowout.
Q. We are having problems when cutting some of the brittle granites with pieces breaking off when the saw is exiting the cut. We have tried slowing the speed down and still are having problems. Is there a way to cut these pieces without breaking them?
A. The best way to solve this problem is to place a scrap piece of stone up against the end of your cut. Also slow the saw down as you get toward the end. This should solve the problem.