The statement: “A band saw blade is a band saw blade is a band saw blade,” isn’t true, says Glenn Tatro, director, technical sales, LENOX. There’s a lot more to cutting with one than you might think, and how saw blades are made separates the best from the rest.
“Working in the bandsaw-blade business for the last 31 years, I’ve developed a nice portfolio of the customer-perceived bad-blade syndrome,” says Tatro.
An all-too-often example of that is stripping the teeth out of a blade within the first couple of cuts, putting the blade back in the box, getting the marker out, and in big bold letters across the front of the box, writing BAD BLADE remarks Tatro. Periodically anyone can have a blade that is not up to specs. However, at times there are other culprits that cause bad blades. For example, a break-in procedure wasn’t used, the wrong band speed was used or the feed pressure was in excess of the capability of the blade.
Tatro mentions that there are two types of customers who buy bandsaw blades: the ones who saw for a living and the ones who only saw when they have to.
“Lack of education on the proper use of a saw blade and the lack of preventative maintenance on the bandsaw machine can dramatically affect the life of a bandsaw blade,” he says. “If the customer lacks either one of these, then a bandsaw blade is a bandsaw blade is a bandsaw blade.
“Many times, customers that don’t saw for a living aren’t aware of the proper speeds and feeds and how they correlate with an efficient cut and blade life. They often don’t understand how their equipment can work most effectively for their operation,” he remarks.
“In most cases, customers that saw for a living understand the importance of being educated on band saw blade usage and have a preventative-maintenance program in place for their saws.
“They are truly looking at the cost of the saw blade versus the price of it. These are the customers who don’t buy on price, because they know that the price is the smallest part of the equation in their sawing operation. “Don’t try to tell them there isn’t a difference in saw blades,” he says.
Dale Petts, Simonds, Global Product Manager, Metal Cutting, adds, “When we train our representatives, we teach that a bandsaw blade is series of precision cutting tools on a terrible tool holder. For a blade to wrap itself around the wheels of the bandsaw machine, it has to be on a spring-steel backer. This is the (terrible) tool holder. Most cutting tools are either solid carbide or have a very rigid tool holder. Bandsawing is uniquely deficient in this way. To help alleviate this deficiency there is a tensioning mechanism on every bandsaw machine to stretch the blade tight. There is, however, a limit to what you can do to help hold that blade straight, flat and true without drawing it so tight that it fatigues prematurely or pulls apart.”
Most of the blades used today are bimetal. This means that they are actually a two-piece blade. All bimetal blades are made out of some sort of backing material and the teeth are made out of high speed steel (HSS).
The HSS is a very thin strip of steel that will become the tips of the teeth on the blade. There are a number of different grades of HSS used to make band saw blades. The backing material and the HSS are welded together to form one piece of material called bimetal-strip stock.
The bimetal-strip stock makes the blade backing durable enough to handle the stresses of being tensioned up to 30,000 psi and then bending around a set of wheels and twisting up to 90 degrees into a set of guides. This is where the importance of the backing steel becomes evident very quickly.
There are differences in the HSS that is used for the tooth side of the bimetal strip stock. Some of the steel used might not have the heat, wear or shock resistance that another might have. Considering the fact that heat and vibration are the two major enemies of a saw blade, the type of HSS used is extremely important.
“The processes that a saw-blade manufacturer uses in transforming the bimetal-strip stock into a bandsaw blade can be the most differentiating factor for the customer,” mentions Tatro.
It could be a matter of how the teeth are cut. Whether a milling cutter is used to mill the teeth into the stock or whether the teeth are ground in using a grinding wheel.
Tooth geometry and rake angles, along with how the teeth are heat treated and set from side to side to produce the kerf, are all very important components in filling the needs of the two different customer bases. These variables play an important part in giving users a bandsaw blade that will provide them with the lowest cost per cut or one that doesn’t make the cut.
“We use some innovative methods in our manufacturing process that yield greater straightness, flatness, uniformity, tooth height and sharpness at the cutting edge. When these are combined together, they give us some advantages over what our competitors are doing,” says Petts.
“Some of our manufacturing process is proprietary and some of our performance has to do with the unique way we now heat treat our product,” he adds.
Some time ago the sawing industry migrated to variable-pitch bandsaw blades mentions Petts. “Vibration is inherent in bandsawing, because you have a spring-tempered ribbon of steel stretched around a pair of wheels in the machine.
“When drawn tight, the blade wants to play (vibrate) like a guitar string while cutting. The tone being played represents vibration, which is a contributor to poor tool life. For that reason bandsaw-blade designers space their teeth at varying distances within a pattern to help break the tendency to vibrate, although it often remains a problem.”
Simonds discovered a key to further reducing vibration. They minimally, not radically, vary tooth spacing Petts remarks. “We discovered an algorithm for tooth spacing that allowed us to optimally reduce vibration while coming closer to the ideal condition where all teeth are uniformly spaced and thus wear uniformly.
“By throwing out the conventional tooth spacing formulas, we can achieve even lower vibration levels and improve tool life,” he says. “We wanted to develop a more robust product that would handle some of the shock and abuse that happens when you have a machine or operator that isn’t terribly sophisticated. By making the largest tooth in the pattern slightly smaller, and the smallest tooth in the pattern slightly larger than the industry norm, combined with a new algorithm of tooth spacing within the variable pattern, it all added up to a unique, robust and versatile recipe for a better, and ultimately patentable, bandsaw blade.”
Ed Nichols, technical services manager at DoAll, adds that milling cutters are often used to cut the saw teeth, but as cutters dull, they leave striations that affect chip flow within the bandsaw blade gullets. The striations are also places where fatigue cracks begin to develop.
“We grind most of our blades. This gives us a consistently smooth finish on the tooth surfaces, and chips flow better. We achieve more consistent tooth height, because we redress the wheel after grinding each section of blade.
“We use a powder-metal grade of HSS for the teeth of our premium blades. Powder metal is not only significantly more wear resistant than the M42 HSS commonly used in bi-metal blades, but it’s also very tough. So it stands up better when cutting materials that require a very sharp edge to penetrate.”
Petts adds, “It is pretty easy to understand that if a blade is manufactured and the teeth vary in some way or don’t align properly, it causes some teeth to work harder than others. This lack of load uniformity reduces blade life. We recently received patent protection on our A8 Broadband Bandsaw Blades that use the improved-wear algorithm along with improved vibration reduction.”
The company’s idea behind the patented A8 Broadband blade is that people don’t want to change the blade for different material types, shapes and sizes. Simonds understands the productivity gain and inventory advantages a user can get by just leaving the blade on the machine and not constantly changing tooth sizes and geometries.
“By using a nominal-rake angle on our A8 Broadband products, combined with the rationalized tooth spacing, we get a uniform distribution of chip loads that gives us wear improvements and the ability to cut a very wide range of materials from aluminum to stainless steel with the same blade,” says Petts.
Purchasing a bandsaw blade
When purchasing a bandsaw blade, as with most metal cutting applications, it’s more about what’s being cut to get the proper performance from the blade. Along with this, the equipment and cutting setup can play an important part of getting the most out of a blade.
As most bandsaw-blade companies mention, there really isn’t a blade that can cut everything efficiently, but some companies are working toward this goal.
“We are a manufacturer of bandsaw blades, bandsaw machines and cutting fluids,” says Darren Garbutt, General Manager of DoALL Sawing Products. So this forces us to look at saw blade applications from a three-legged-stool approach. For instance, if there’s a perceived problem with the blade, it might actually be the machine or the cutting fluid and not the blade at all. We like to look at challenges from all three of these perspectives and approach our customer as a solution provider.
“Ultimately we sell them on the productivity of our bandsaw blade. We want our customers to understand this. When applied properly, our blade will outperform our competitors. We look at test results and we guarantee our performance.”
Petts mentions that Simonds also manufactures a wide range of bandsaw blades engineered to specific applications. “We do have general purpose bandsaw blades, but we also have a series of high performance ones.
Tatro adds that users must understand that in a sawing operation, 90 percent of the overall cost is how long it takes them to make their cuts, seven percent represents the coolant used for the cut, including its disposal, and three percent is the price of the blade.
“Everybody focuses on the price of the blade, and that’s what they go after. They think that a lower-priced blade is a better deal for them, and they switch products, but that’s not what they should be looking at,” he mentions.
As with any tool a fabricator uses, learning about them and how they should be used is important. To this end, Simonds offers an online user course to help operators better understand sawing. However, you must be sponsored to use the course. See a Simonds representative and go to: www.neveryieldtosteel.com to learn about sawing.
A short history of bandsaw blades
Up until 1954, bandsaw blades were made from a 10125 carbon steel, mentions Ed Nichols, technical services manager at DoAll. Teeth were flame hardened, and the backing might or might not have been spring tempered to around 45 Rockwell C. Its shortcoming was that it could only tolerate tooth temperatures up to about 400 degrees F when cutting. Beyond this temperature, teeth would begin to soften, deform and dull.
This limitation kept bandsawing speeds much slower compared to today’s blades.
In the early 1950s, DoALL introduced bandsaw blades made entirely of high-speed steel (HSS). The benefit was that teeth could withstand temperatures up to around 1100 degrees F before softening and dulling. Therefore, they could be run much faster than carbon-steel blades. However, HSS wasn’t a good backing material. It was difficult to butt weld, and it didn’t stand up very well to the stresses of bending and twisting encountered in bandsawing. Therefore, blade life was sacrificed for faster cutting rates.
Then in the 1960s DoAll started making bi-metal bandsaw blades by welding a HSS-wire strip onto an alloy-steel backing. “There are many steps to making this type of blade, but this gave us the best of both worlds,” concludes Nichols.