Bi-metal versatility

The development of a bi-metal saw blade offers manufacturers more versatility in materials


Whether the goal is to make quick work of cuts or to achieve a quality finish, most saw operators share a preference in regard to avoiding downtime associated with replacing bandsaw blades. There’s also the expense to consider when a blade fails and needs to be swapped out with a new one.

When speed is of the essence and cut quality is not important, manufacturers see value in burning through blades in order to meet production goals. For others, reducing secondary work is the goal, which requires a clean, quality finish and possibly slower cutting speeds. In the development of saw blades, engineers carefully study the way chips are made as the teeth pass through the material, as the chip shape, size and thickness indicate blade performance.

Bi-metal blades have been developed to offer fast, quality cuts on ferrous and non-ferrous metals, but they also hold up to the rigors of fast-paced cutting and, when used correctly, last a long time.

Most bi-metal blade manufacturers use a high-speed steel for the blade’s teeth, bonding it with a variety of methods, such as laser beam welding or electron beam welding, to a high-strength carbon steel base. With this combination, operators get the cutting speed they’re looking for as well as the durability that non-bi-metal blades lack.

Saw blade manufacturer The L.S. Starrett Co. has taken bi-metal blade manufacturing to another level with its patented bi-metal unique technology. Cutting with conventional bi-metal blades can result in heat build-up in areas creating a heat-affected zone, which compromises the integrity of the metal. However, the bi-metal unique process eliminates the heat-affected zone, which helps reduce tooth-stripping problems.

The bi-metal unique technology is featured in Starrett’s Intenss line of bandsaw blades. Jay K. Gordon, Starrett’s North American sales manager for saws & hand tools, says there is power behind the Intenss blades due to their M-42 steel (one of seven types of high-speed steel) teeth with a multi-edge tooth design that produces split chips for faster cutting.

Production method

The patented bi-metal unique technology joins two strips of high-speed steel wires to a backing steel in a solid phase, using the principle of solid-state diffusion bonding.

“The solid-state process uses only 10 to 20 percent of the amount of heat that is found in a welding manufacturing process,” Gordon says.

With the patented bonding process along with the high-speed steel and the high-strength carbon steel base, Starrett produces blades that achieve faster cutting speeds without compromising quality, Gordon says.

Another tooth-strippage deterrent involves weld contact between the backing material and the teeth. Gordon says the bi-metal unique technology provides 170 percent more weld contact with the teeth, which means the Intenss blades exhibit a significant reduction in fracture and breakage, which enables exceptionally long blade life.

During the diffusion bonding process, an advantageous tooth geometry is created, adding yet another perk to the Intenss blades. For example, the high-speed steel wires are bonded to the sides of the strip and the fusion zone (the portion of the metal that has undergone melting) is parallel to the teeth, which creates a grooved-tooth geometry.

“The grooved-tooth geometry produces two cutting surfaces separated by the blade,” Gordon explains. “Soon after initial use of the blade, the teeth develop a U-shaped groove that is 0.001 in. to 0.002 in. deep between the two high-speed steel edges, altering the blade area engaged in the cut. The groove remains at a constant depth and wears at the same rate as the teeth.”

Dual chips, also referred to as split chips, are the result of the grooved-tooth geometry. The bonus is that they are easily removed from the cut, which is important because when chips remain in the cut, they run the risk of packing the gullets and bonding to the teeth. Split chips are more easily removed because they curl and fall away from the cut. Gordon says they refer to this as the “split chip advantage,” which provides 25 percent faster cutting than blades made with conventional electron beam welding.

“The groove also permits increased coolant flow to the cutting surface,” he says. “Proper coolant flow not only cools and lubricates the blade, it also flushes out chips that are caught in the spaces inside tubes.”

Bi-metal options

Gordon refers to the bi-metal Intenss blades as the ideal “affordable workhorse” blade for general sawing in toolrooms, maintenance shops, and fabrication and machine shops. He explains that even though it is a multi-purpose blade, it’s designed to cut a variety of materials quickly and efficiently. The Intenss line is bringing affordable, multipurpose technology to the market suitable for tubes and profiles, solids, structurals and sheets in a range of materials such as carbon steel, aluminum, copper, brass, cast iron, alloy steel, stainless steel and more.

Starrett’s Intenss brings new technology to the market, but the company has other bi-metal blades that also serve specific purposes. For example, Versatix MP bandsaw blades are commonly used for structurals, tubes and small solids. The line features a triple-tempered, high-speed steel material and utilizes M-42 teeth and an alloy steel backing strip. Starrett has patented the tooth design, as it dissipates stress during cutting, which reduces tooth breakage and leads to longer blade life. The blade is made using the bi-metal unique technology.

For operators working with heavy-duty materials, such as tool, high-speed, stainless and hardened steels, Starrett offers Primalloy bi-metal bandsaw blades. They are also used for cutting nickel and titanium alloys.

Primalloy blades offer a “cost-effective, highly productive sawing solution,” Gordan says. “The cutting performance, as well as heat and wear resistance of Primalloy’s M-51 high-speed steel, is greatly increased through alloying with cobalt and vanadium.” Furthermore, the proprietary extended life treatment applied to the alloy steel backing material results in “significantly longer blade life due to reduced fatigue.”

“Bi-metal blades typically have a less aggressive rake angle and a tooth shape specifically designed to perform well on solids and structural materials,” he says. “The more ‘high-performance’ or ‘production oriented’ blades tend to be specials, providing the highest possible production on either structurals or solids, but not both.”

Finally, Starrett’s Univerz bi-metal PortaBand saw blades (used on portable handheld machines) also use the bi-metal unique technology. They are popular with a variety of users including construction and maintenance workers and at metal workshops. Gordon notes this is because they are known for fast cutting, but also offer “exceptional life in challenging applications, including contour cutting.”

The L.S. Starrett Co.

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