Structural Cutting

Saw blades with high-speed steel and improved tooth geometry offer a quieter, more efficient way to cut through structural material


Bottlenecks are the bane of production facilities and there are innumerable reasons for them. It wasn’t that long ago that bottlenecks occurred at one of the first steps in the manufacturing process – the bandsaw – because of the blade.

Carbon steel blades, which dulled quickly, caused a pause in production while they were switched out for new, sharp blades. But they were the go-to blade on bandsaws in production facilities of the past as that was the best option, until bi-metal blades were introduced, providing somewhat of a reprieve from the all-too-frequent production delays.

Even after the introduction of bi-metal blades, which provide longer life than carbon blades, there were still challenges associated with cutting structural shapes, such as tubes, pipes and profiles. The challenge, says Jay Gordon, North American sales manager, saws and hand tools for The L.S. Starrett Co., is the ability to maintain the minimum number of teeth in the material while dealing with interrupted cutting.

The Tennax-Pro utilizes tough M42 steel to offer more accurate cuts and prolonged blade life.

“While cutting shapes such as tubes and profiles,” he says, “the material thickness often varies, making the tooth pitch to be either too fine or too coarse to make productive cuts. This can lead to excessive loading of the gullets and typically prevents the teeth from being able to penetrate the material properly, resulting in the teeth ‘slapping’ the material as they enter the thinner parts.”

When this “slapping” occurs, the teeth are damaged and blade life suffers.

“Some structural shapes are softer carbon steels,” he says, “and as such, are not particularly hard, so they tend to cut relatively quickly. That’s not to say all shapes are soft, but most are. Given the interrupted cut nature of these shapes, they can be the most challenging and hardest on the blade to cut.”

Introducing M42 steel

High-speed steel, which in the manufacturing industry is referred to as HSS, has been used in saw blade production for decades. One of the first was a metal called M2 HSS, which is a general-purpose tungsten-molybdenum steel considered a tough material capable of wear resistance. M2 made its introduction into manufacturing in 1937, becoming one of the first mass-produced high-speed steels.

Cutting I-beams offers challenges as the saw blade enters and exits voids, which can lead to pinching. Thanks to the Tennax-Pro blade tooth geometry, these risks are minimized.

More advancements quickly came, such as M35 HSS, providing better heat resistance than M2. The addition of between 8 to 10 percent cobalt to M2 HSS created an even tougher material, called M42. M42 has improved “red hardness,” which refers to its performance at high heat. The hotter the metal gets, the more likely it is to soften, but M42 performs well at high speeds and at high heat. Gordon says that as M42 became more affordable and available, it took the place of lesser quality blade material, and is a top choice for Starrett’s bi-metal blades.

“In most instances,” he says, “M42 has become the standard bi-metal blade throughout the industry.”

New, improved blades

Implementing better blades is about more than just reducing consumable costs. And while high-production facilities can burn through a hefty sum of blades and using tougher, longer-lasting blades is certainly an improvement, solving ongoing issues, such as tooth “slap,” can lead to better quality cuts. But what about the noise factor? Does the sound of a blade going through metal really matter that much in a production facility?

“While noise may not sound like much of an issue,” Gordon says, “you will find that many, if not most sawing operators, complain about noisy blades.”

Some of these complaints are simply due to the nature of cutting structural shapes, but noise is also an indication of vibration.

“The less vibration, the longer the blade life,” he says. “While no blade will be silent, especially when cutting structural materials, Starrett has designed its new Tennax-Pro blades to significantly reduce vibrations when cutting, which in turn quiets the blade.”

In addition to being quieter and less vibrating , the blades feature new tooth geometry, dissipating stress during cutting for greater resistance to wear and tooth breakage as the blades move in and out of materials, such as challenging tubes, pipes, profiles and structural shapes in both single piece and bundles.

The tooth geometry also accounts for pinching, which can reduce the life of a blade. Pinching occurs when the material, which is under stress during the cutting process, closes up on the blade. While tubing does not tend to have much of a pinching or stress issue, most other structural shapes such as channel, I-beam and H-beam do have these issues. This is caused by the inherent stresses in the material and once the cutting begins, those stresses tend to make the material close up on the blade.

“The new special tooth-setting process in the Tennax-Pro allows for a larger kerf,” Gordon says, “which allows a certain amount of stress relief in the material without pinching the blade.”

Blade best practices

Getting the most out of a blade, whether it’s the lifespan or the cut quality, requires a knowledge of how to address speed and feed guidelines, which govern the speed at which the blade moves and the amount of material it processes per minute. Gordon says speed and feed are determined by the type of material, not necessarily the size of the material.

“In general, material can be broken into three groups,” he says, “hard, medium and soft. While there are nuances to each of these, if you can group your material into one of these categories, you will be able to better estimate blade speed and feed.”

From tubes to I-beams, the new Starrett blade offers fabricators a more durable solution for avoiding downtime related to replacing worn blades.

Gordon adds that, in general, the harder the material, the slower the band speed. But with most structural materials, speed and feed are usually in the “soft” category.

“However, there are also hard structural/tubings being cut,” he notes. “For quick estimates, soft materials may fall in the 300 sfpm range, while hard materials will be in the 100 sfpm range with medium falling in between.”

An important note Gordon has for bandsaw operators is in regard to the fact that most production bandsaws have a feed rate (traverse control) adjustment and a feed pressure adjustment. These two controls, he says, are important and should change with the type (hardness) of the material.

“In essence,” Gordon says, “they work completely opposite from one another. Feed rate is the speed at which the head comes down or moves forward. Feed pressure is how much pressure is being applied to make the head move. In general, the harder the material, the more feed pressure is needed to penetrate the material; however, hard material cannot be cut fast, so typically the feed rate would be lowered. In soft material the opposite is true – lower feed pressure and higher feed rate.”

The L.S. Starrett Co.

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