The phrase “the right tool for the job” comes into play plenty in manufacturing, and it’s especially true for sawing operations and, in turn, blade selection. Whether the desired outcome is to have a clean, quality finish or if it is to cut through as much material in the fastest time possible, there is a tool (blade) for that. Knowing the right blade for the job, however, comes down to multiple factors.
Soft materials, such as aluminum and copper, are easier to cut than harder materials, such as carbon steel, but the soft materials prove more cumbersome under the teeth of a saw blade. Jordan Schimel, Starrett’s product manager for saws and hand tools, says non-ferrous material like aluminum have low melting points compared to harder materials.
“If you do not take proper precautions,” Schimel begins, “the heat created when cutting can easily result in loading molten aluminum into the teeth of the blade, rendering it glazed over and useless.”
Additionally, the saw operator must consider that while they can get away with a higher feed rate, they must control factors that influence chip load.
“If you overload the gullet of the tooth,” Schimel says, “it can cause a lot of issues, such as teeth chipping off the backing and the blade jumping around in the material. One additional consideration is that while soft materials are easier to cut, it can be more challenging to get a desirable finish when you consider the actual micro-level mechanics of the material separating from the blade tooth.”
Schimel says choosing the wrong blade, namely one without a positive rake, can cause the saw operator to compress the material’s microstructure, making it harder while cutting it.
“Softer materials may appear easier to cut,” he says, “but it’s important to take equal amounts of care when cutting these materials so you don’t create scrap or ruin your blade.”
Jay Gordon, Starrett’s North American sales manager for saws and hand tools, agrees that a common issue when cutting soft material is chip loading.
“Gullets can fill up before exiting the material,” Gordon says, “and can cause everything from rough cuts to tooth strippage.”
A way to combat this issue is to lean toward a coarser blade rather than a fine-tooth blade. Gordon says this will allow the gullets to resist compaction and “hopefully clear the material before being completely filled up.” Also, he notes that soft material does not require much feed pressure in the sawing process because it doesn’t take much pressure for the teeth to engage the material.
“When cutting soft materials, such as aluminum and copper, the best approach is low feed pressure, higher feed rate and much higher blade speed,” Gordon says. “This will allow for good blade penetration and removal of chips in a timely manner.”
Starrett’s Intenss Pro bi-metal bandsaw blade line is a recommended blade type for users in need of a blade that will last; and it can be applied to soft and hard materials alike. Gordon says there are some end users who prefer to use carbide blades over bi-metal blades when cutting aluminum because the blades have larger tooth pitch size. However, the disadvantage with carbide blades is that they don’t last as long as bi-metal blades.
When cutting through hard materials, such as carbon steel, gullet loading is a rare concern because the hard material doesn’t tend to load up the gullets the way soft does. This allows more teeth to be used when cutting hard materials, increasing productivity. Gordon notes that a major difference between cutting hard and soft materials is that hard materials require more feed pressure, which enables better tooth penetration.
“These types of hard materials cannot be cut quickly,” Gordon says, “so a lower feed rate and a slower blade speed are used to allow the blade to penetrate the material and pull the necessary chip load throughout the material.”
Schimel adds that Starrett’s Primalloy, Intenss PRO-VTH, Advanz MC5 and MC7 blades are designed for hard materials.
“Superalloys are a breeze to spec in,” Schimel says of the various blades designed for hard materials. “Not only does Starrett have blades that are manufactured to solve specific application challenges, but when you attend to all of the details that a Starrett saw specialist and sales representative take when qualifying a blade for an application, it is actually a fairly straightforward task to provide a blade that exceeds longevity and cutting rate requirements. This ensures that we can reduce consumable costs effectively by meeting the desired cut rate and extending the life of a blade, often by many hours of the sawing operation.”
Gordon says that it is “generally true” that a saw operator can go through more blades when cutting hard materials, but it depends on which hard and soft materials are being compared. Several blades within the Starrett bi-metal bandsaw blade line can result in increased blade life. For example, Gordon says the M51 HSS (high-speed steel) Primalloy bi-metal blades can achieve cutting speeds comparable to blades made with M42 HSS and provide longer life.
“M51 offers a better wear resistance and increases blade life,” Gordon says. “Primalloy is designed for heavy-duty cutting applications. The cutting performance of the HSS is greatly increased through alloying with cobalt and vanadium. These alloying elements substantially increase the heat resistance as well as the wear resistance.”
Saw operators need to also consider the size of their material when choosing a blade. Schimel says the primary consideration is choosing the proper tooth per inch (TPI)/pitch for the
specific dimensions of the material.
“The ideal operating parameters are to have between six and 12 teeth in the material,” Schimel says, “and you should always measure this from the widest point of the material being cut. These factors change if the material isn’t solid, but we can run appropriate calculations, depending on the wall thickness, to obtain the best TPI/pitch for your application. By considering these rules, you will quickly see that you need a different TPI for a small-diameter cross section than a large one.”
But what about a scenario where different size materials are being cut with the same blade? Gordon says this is a situation where TPI/pitch will be difficult to maintain. His suggestion is to determine what size material is being cut most often and choose the right TPI/pitch for that material.
“If the tooth pitch is not severely over or under the true specification,” he says, “then many times an adjustment of the feeds and speeds can suffice to allow the blades to perform.
Interrupted cuts prove to be one of the main challenges when cutting bundles, but variable chip loads are another concern. To address these issues, Gordon recommends taking a close look at tooth pitch size when choosing a blade to cut bundles.
“Depending on the material being cut, you might typically use a 5-8 TPI/pitch,” Gordon says, “but when bundled, you may need a 3-4 TPI/pitch – when any solid portion of the bundle is large enough to justify it. Secondly, and perhaps most imporant, is to consider the clamping. Any time a bundle of material is cut, the material has to be clamped in such a way to negate any and all vibration. This typically involves side clamps as well as top clamps. Vibration is the No. 1 reason for poor blade life.”
Starrett has bandsaw blades designed specifically for bundled materials. For example, the Versatix MP is a bi-metal blade featuring triple-tempered, high-speed steel M42 cobalt steel teeth with an alloy steel backing strip.
“It has a patented tooth design that dissipates stress during cutting for less tooth breakage and longer blade life,” Schimel says. “Its special tooth set minimizes pinching when cutting structurals and bundles.”
A multi-factor approach
For saw operators using a one-size-fits-all blade, Schimel says, “there should be sirens going off and red flags going up.” The reason being, every operation has something different about it that should be taken into account when choosing a blade. He recommends looking at the whole picture when choosing a blade.
“For example, blade cost, longevity and cutting speed are all important factors to consider upfront,” he says. “Also, consider what type of saw it is – vertical, horizontal, hydraulic or gravity-fed. The best blade for the job on a hydraulic saw will be different one for a gravity-fed saw due to the way the materials are engineered to perform.”
Starrett has a highly educated saw specialist team that covers North America, checking all the minute details in their customers’ applications, such as feed rates, the quality of coolant and other factors that could be missed in a situation where so much of the sawing process is automated.
“These saw specialists are available for shop visits, phone calls, video conferences or by e-mail,” Schimel says,” with a goal to get you the best possible, dialed-in saw for your unique applications.”