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Sawing/Cutting
Friday | 12 March, 2021 | 11:46 am

Blade runner

Written by By Corinna Petry

Above: Starrett Advanz MC7 band saw blades use a progressive four-tooth grind that creates seven distinct chips. This results in less wear compared with conventional triple chip. The four-tooth grind is very effective on nickel alloys, stainless, tool and heat-treated steels.

Blade runner Start with information, access technical support and pay attention to operational details

March 2021 - Service centers and fabricators that are serious about getting the greatest-quality cuts and efficient output from their sawing operations can access a plethora of tactical resources from their vendors, including from the makers and distributors of saw blades.

Jay K. Gordon, North American product manager for sawing and hand tools at The L.S. Starrett Co., explains why everything from YouTube tutorials to tension setting will help sawing operators achieve their goals.

Digital tools

Saw operators, even beginners, can access information in many ways. “We have catalogs, with part numbers, recommended feed and speed rates and an overview of general problems and solutions,” Gordon says. “That’s a great place to start. We have YouTube pages with many videos for band sawing. We answer a lot of questions there.”

For over 140 years, Starrett has made a wide range of precision measuring tools/gauges, metrology equipment and saw blades for metals applications and more. The company published a speed-and-feed guide online for bandsaws. “You just point the arrows and get results,” says Gordon.

The company is currently updating its online calculator, with which users can punch in variables, such as type of materials, thicknesses and diameters and more, and the calculator will make recommendations on how to optimize sawing those materials. There is also an app in the works to do this on mobile platforms.

Now, with all the COVID-19 related issues, Starrett, its distributors and customers often use GoToMeeting and Zoom calls to facilitate and obtain support. “We are doing a lot [virtually] to keep people up to date. Virtual meetings are available for one-on-one chats between a product specialist and customer. We can talk about technical issues,” Gordon says.

“When I started in the business years ago, some of these resources were not available. The younger generation is especially comfortable with such access. Many people do try the digital route first, and we are there to help them.

“The more information we can put in people’s hands, no matter the method, the better off we all are,” Gordon says. “We also encourage in-person meetings, which surely will increase again as the pandemic subsides.”

MM 0321 sawing image1

The Primalloy saw blade is designed for heavy-duty cutting applications. Cobalt and vanadium offer greater heat and wear resistance.

Honing advice

For skilled operators as well as novices, Starrett has recommendations about how best to break in a new blade. “The best analogy is when you sharpen a pencil and push on it too hard, the tip breaks off,” says Gordon. “But if you use the pencil more gently, which smooths the tip, it won’t break when pushed hard.”

Likewise, when a blade comes from the factory, the edge is extremely sharp. “If the edge is too ‘skinny,’ it may be brittle and as the blade enters the material, if at full speed, the edge of the blade deforms or cracks. But if you back off on feed rate and pressure, the blade works less hard, and hones the tooth, making it stronger,” he says. “So when you decide to go into full production, the tooth lasts longer as it is broken in.”

Tension setting

Gordon advises saw operators to check the tension on the blade so that they avoid issues that lead to inaccurate cuts.

“You can use a handheld gauge to assess the blade tension. If the blade is loose, tighten it up by hand or mechanically. Then test it again.” Some customers may use a hydraulic gauge that shows pressure, from which they can calculate tension.

“Many smaller, general-purpose saws have a little dial, giving the size of the blade, or a spring wheel that stops when the correct tension is achieved. These work well but an actual gauge measures the true stretch of the blade to match manufacturers’ recommendations.”

Gordon says 30,000 psi is a normal tension. The dials “could be 100 percent correct but you never know until you check it directly,” he adds. Tension keeps the blade tight between each guide. “The tension holds the blade straight and firm, and won’t cause issues. If it’s off, the finish cut is horrible and the blade life shortens.

“You can also have a negative effect on the machine itself, including wear and tear. No matter the machine manufacturer, the blade should be tensioned properly for the machine and for the material being cut.”

Coolant’s role

Coolant is designed to remove heat and lubricate the teeth to prevent chip welding. “Coolant designed for band saws will work well in most other machinery but the reverse is not necessarily true,” according to Gordon. Many operations want to buy one type of coolant for everything but there are synthetic and semi-synthetic coolants, soluble oils, misters and cutting oils.

“At one point, straight cutting oil was a viable solution. But there are EPA issues and fire hazards to consider, so most shops don’t use that anymore. Synthetic and semi-synthetic oils won’t spoil as quickly. They offer a good amount of cooling and lubrication properties,” Gordon says.

Coolants used for drilling, milling and tapping are not the same as those required for sawing. “Sawing processes need a heavier mixture—5 to 1 to 10 to 1 [water and coolant] mix ratio.”

Users should just follow labeled instructions when mixing. “You don’t want to have oil and water separate. Avoiding separation is important. Cleanliness is important, too. Manufacturers generally recommend changing the coolant at least once a year based on an 8- or 10-hour day, more often with a two-shift operation. This is a forgotten part of sawing production. People throw it in and turn a crank, but it cannot be neglected,” Gordon says.

MM 0321 sawing image2

A Primalloy blade cuts through large-diameter bar. Coolant mixing and maintenance are important.

Chip brush monitoring

A key challenge to avoid in sawing operations is chip welding, where due to built-up heat and pressure, a chip from the material being cut gets permanently stuck in the blade.

“The cause is usually a combination of heat and pressure,” says Gordon. “If you don’t have lubrication, the tooth and chip are so hot that they spot weld together.

“Every blade manufacturer strives to make the gullets and tooth shapes just right,” he says. “The minute a chip is welded to the blade, the design of the blade has been changed.”

Chip brushes, a standard feature on saws, don’t automatically solve that problem, he notes. “You have to have the right coolant, feed and speed. If you push material too fast, the coolant won’t solve the problem. If chip welding occurs, something is wrong.”

Chip brushes are designed to take chips out of the gullet, but only loose chips. They are not designed to get welded chips out.

Most saws run one of two types of brushes: a steel wire wheel, or a polymer wheel (nylon). “The polymer doesn’t load up with chips but sometimes the steel wire will. However, the steel wheel typically cleans the gullet better. By maintaining each wheel type, the wear is reduced,” says Gordon.

Over time, however, “a 3-inch wheel becomes a 2 3/4 inch wheel that is barely touching the blade, so operators have to be aware of that.”

The main thing is to turn to the blade manufacturer or distributor as a ready resource and keep on top of the tasks that will keep the sawing operation running in a highly productive manner. MM

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