Two representatives from Simonds International offer five tips for avoiding common bandsaw mistakes.
Modern Machine Shop, David Rosing,
Technical Manager of Bandsaw Products
, Ron Saxon,
National Accounts Manager
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Friction resulting from heat generated by the cutting process can cause chips to weld in blade gullets, degrading cut quality, productivity and blade life. Running at the right parameters, using proper coolant, correctly positioning brushes, setting the right tension and properly breaking in the blade are all critical elements of an effective sawing process.
Bandsaws are very much like the people who use them—they don’t react well to heat, shock, abrasion, stress or tension. Most sawing mistakes result in one or more of these conditions, all of which can reduce productivity, blade life and cut quality. With the economy recovering and factories coming back to life, this is no time for slip-ups, so let’s sink our teeth into five tips that can help avoid some of the most common sawing mistakes:
• Get your parameters right. We all feel the need for speed, but your blades can really feel the heat when you run them too hard or too fast. Excessive feed rates, pressure and speed can dull blades, break teeth, snap welds or crack the blade’s back edge. Another risk is chip welding, which occurs when heat from cutting friction welds chips into gullets, or the spaces between the blade teeth. This can degrade cut quality, strip teeth and crack gullets.
To avoid these problems, set your machine to the correct blade speed and cutting feed rate for the material. As a general rule, slow the blade speed for tougher materials and increase speed for softer materials. For specific information, check your operator’s manual or the feed rate chart on your machine. Alternatively, your blade supplier might offer online educational resources and calculators that can help determine the correct parameters.
• Keep your cool. Many of the problems described above can also result from improper application of cutting fluid, which cools the blade, lubricates the teeth and washes away chips. Most cutting fluids must be mixed with water, and coating and lubricating a bandsaw blade throughout the entire cut requires a richer mix than other types of machining applications. As the coolant recirculates, be sure to replace any water that evaporates from the mixed solution. You should also be on guard for leaks and the possibility of chips flying into the system and blocking coolant flow.
• Give your blade the brush-off. To avoid chip welding, your machine should have a rotating wire brush that is properly positioned to continually whisk away chips and debris during the cut. Setting the brush too far from the teeth prevents the filaments from effectively removing chips from gullets, while setting it too close can prematurely wear blade teeth or the brush itself. The brush should reach in and touch, but not go beyond, the deepest portions of gullets. Of course, that assumes your machine has a brush in the first place—having no brushes at all is a significant and all-too-common problem.
• Avoid tension. Hypertension isn’t good for anyone or anything, especially your bandsaw. Setting blade tension too high can break bands, crack gullets and wear out machine bearings. On the other hand, setting a blade too loose can lead to poor beam strength, band fatigue or crooked cuts. Most blades work best between 25,000 and 32,000 psi. Use a gage to measure and properly set tension. If you don’t have a gage or know how to use it, give us a call and we’ll give you a free check and help you correctly set blade tension.
• Apply the breaks. You need to break in your blade just as you would a new car or pair of shoes. This will “hone” the teeth and extend blade life. Think of brand new blade teeth as freshly sharpened pencil tips—if you press down too hard, you’ll break the tip. So, the best way to break in a new bimetal blade is to reduce the feed rate, not the speed.
Although some blades are broken in at the factory, we still recommend using a handy formula to ensure your blade is honed to perfection. First, multiply the recommended feed rate (or pressure on gravity feed saws) by 50 percent to determine the break-in feed rate. To determine how long to run at this rate, divide the recommended blade speed by four. For example, if the recommended blade speed is 200 feet per minute, you would cut a total of 50 square inches of material. Once you approach the end of the break-in period, gradually increase the feed rate back to normal.
Even as you work hard to keep pace, there are no shortcuts to optimal performance—yours or the blade’s. Take time to get the information you need to do the job right, and cut out those mistakes.
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