November 22, 2010
The process of deciding between a band saw and a cold saw is not always clear-cut. Here are some short answers to this and other frequently asked sawing questions
In the world of metal sawing, the process of deciding between a band saw and a cold saw is not always clear-cut. Mike Albrecht, national sales manager at Scotchman Industries Inc., Philip, S.D., guides fabricators through this process and other sawing-related questions every day.
Practical Welding Today® spoke with Albrecht and nailed down some of the most common sawing issues that he assists fabricators with.
Albrecht: Before you can decide between a band saw and a cold saw, you first must evaluate your cut quality and volume requirements. It’s important to fit the machine to the application. If you’re bundle cutting large volumes of tube for which weld prep or weld accuracy isn’t a big issue, then a band saw is probably the direction you want to go. If you need an accurate and clean cut right off the machine, then you probably want to lean toward a cold saw.
A band saw is qualified as a capacity-type machine, meaning it can cut a wide variety of materials and volumes. The cut quality is generally good, but it does tend to leave some burr on the edges. A band saw blade is disposable, which means once you have run the life of the blade, you can throw it away and replace it with a new one.
A cold saw provides a clean and accurate cut, but it has a much smaller capacity. In the last 10 years cold saws have evolved into a tool used more by welding shops because of tighter tolerances on cut accuracies. Welding shops need more accuracy in the finished cut, and cold saws can provide that. Cold saw blades are reusable, and generally speaking, you can sharpen the blade 30 to 40 times before it gets too small to cut through the maximum-diameter material.
Albrecht: Matching the right blade with the application is the key. On a cold saw, for instance, cutting solid material using a fine-tooth blade will cause a buildup of chip load, resulting in a poor cut. The key with cold sawing is learning how to listen to the machine. It’s more of a milling process, and that’s what separates it from band sawing. You have to understand that you’re milling a chip with horsepower and torque versus grabbing a chip and cutting. To understand milling you have to understand your speeds, feeds, and chip load. It sounds complicated, but it’s really just a matter of selecting the right chip load. Two variables in chip load selection are RPM, or the surface feet that your blade is turning, and the tooth size. These two factors combined will get you into the world of a perfect chip load.
For cutting thin-walled material you need a fine-toothed blade to control the chip load better. On coarse material such as solid bar, for example, you need a coarser tooth so you can roll a bigger chip through the material.
The same is true with a band saw. If you don’t have the proper teeth per inch, your cut quality will suffer. A telltale sign that you are using the wrong band saw blade is when the teeth are stripped from the blade, which is caused by excessive chip load.
Albrecht: A quality guide system on a band saw can do a lot for ensuring good cut quality. The carbide sandwiched blade guides will help control blade runout, or in other words, prevent your blade from running crooked or veering away from the straight-line cut that you are trying to perform.
Coolant plays a huge role in the cutting process. Just to be clear, when we say coolant in relation to cold saws, we’re actually referring to lubricant. I can make a cut with a cold saw without using coolant and still achieve a cold cut—that’s where the name comes from. So the coolant, or in this case lubricant, isn’t necessarily used to cool the blade or the material. It does, however, serve as a lubricant between the blade’s teeth to help it last longer between sharpenings.
Coolant serves a similar purpose in band saw cutting. More and more systems are heading toward advanced coolant or lubricant systems, such as a microlube system that applies very little coolant to the blade to minimize runoff or environmental issues. As a matter of fact, some welding applications cannot tolerate coolant on the material. In these cases, fabricators must use a vegetable oil-based coolant, which, if used sparingly, does not affect the welding process. We see instances of this in many stainless steel applications and others where contamination is an issue.
Another important factor is feeding or measuring the material. Cutting the material is just one process; setting up your part length and accurately measuring it is another. In fact, you’ll probably spend more time measuring and lining up your cut than you will actually cutting. It’s a good idea to employ a cut-length system, which can be added to manual saws up to fully automated saws.
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