Take the most advanced bandsaw in the world and treat the blade poorly and in quick order, that high-dollar machine is reduced to a bottleneck or, at the very least, a new source for piling bad cuts onto the scrap heap. Treat the blade properly, however, and that high-dollar machine will consistently slice through material quickly and accurately.
Whether the goal is speed or the highest quality cut or both, there are a few blade maintenance practices that can’t be ignored if longevity is to be achieved. Considering the blade is the No. 1 consumable in the sawing process, blowing through blade after $90-plus blade can quickly put the hurt on a budget.
DoAll Sawing Products’ Tim Piehel, south central regional sales manager, and Art Allen, southeastern regional sales manager, recently spoke about techniques for extending blade life. Their advice is straightforward and, when followed, can make a significant difference in productivity and the bottom line.
First on Piehel’s and Allen’s to-do list is paying attention to the chip brush – an accessory that knocks the metal chips created during the cutting process out of the way of the blade
and material. Allen explains that when chips aren’t cleared, they gather in the gullets of the blade and re-enter the cut. When that happens, the gullet collects even more chips and overfills, resulting in a “something has to give” situation, which in this case is stripped blade teeth and soon after, blade replacement.
“It’s one of the least expensive wear parts and also one of the most overlooked wear parts on a bandsaw machine,” says Allen of the chip brush. “It’s very important in extending blade life.”
Allen says for optimal performance, the bristles of the brush must not be placed too close to the blade, as this only adds to the problem.
“There is a correct way to position a chip brush,” Allen advises. “You want the bristles barely touching the shallowest gullet.”
Guiding the blade
Like the chip brush, guide arms tend to be overlooked when considering blade life. Guide arms on a bandsaw ensure the blade is making proper contact with the material being cut. Allen says the arms need to be as close to the material as possible and at equal distances on either side of it.
When improperly set, such as in a case where the guide arms are set too far apart from the material, the backing of the blade will deflect upward, which will cause stress cracks in the backing, resulting in a premature break.
“Always position saw guide arms as close to the material you’re cutting as possible,”
Another best practice that many bandsaw operators follow in their routine maintenance duties is to check the condition and adjustment of the guide arms. While the arms are built to hold up to hours and hours of the bandsaw running, they can still wear out, which leads to misaligned cuts and blade failure. Replacing the arms before this happens is part of every good saw maintenance strategy.
Adding to the list of overlooked bandsaw maintenance is band tension. Too much or too little tension on a blade will result in poor performance and poor blade life. And that’s why all bandsaws have a tensioner (higher end saws have hydraulic tensioners) that can be adjusted to fit every individual bandsaw blade manufacturer’s spec on each of their blades. Therefore, dialing it in simply means following the manufacturer’s guideline and using a gauge to ensure it’s right.
“You’re stretching that blade to eliminate deflection,” Piehel says. “When you have deflection, you start getting wear on the teeth, and once the tooth set is gone, the blade will start to cut crooked.”
Most job shops that have a bandsaw in regular use have a tensioner gauge on hand to measure the tension every time the blade is changed and throughout the life of the blade to ensure optimal performance. For shops that don’t have a gauge, Piehel says it’s worth the investment to have someone come in to measure the tension.
Blade break in
Anyone looking to extend the life of a blade by 25 to 50 percent before they even use it needs to break in new blades first. This is a process that hones the teeth and readies the blade for its most efficient speed and feed rates.
“Every time you break in a blade,” Piehel says, “you will get much better blade life out of it.”
The break-in procedure differs depending on blade type. For example, with a new bi-metal blade, Piehel says operators need to reduce the feed force during the first 20 min. of operation to 50 percent of normal. From there, they should gradually increase the feed force in four steps to normal rates over the course of 10 min. Because there’s no need to reduce the speed rate on bi-metal blades, the blade can run at normal speeds throughout the break-in period.
Conversely, for a new carbide blade, rather than running at normal speed during the break-in period, the speed needs to be reduced during the first 20 min. of operation to 70 percent of normal. The feed force also needs to be reduced to 50 percent of normal for the first 20 min. Finally, the blade speed and force feed can be increased gradually in four steps to normal rates over a 10-min. period.
“Think of a lead pencil,” Piehel says. “If I sharpen it with a good point on it, I go to write and I push too hard, the point breaks. What do I do differently then? I don’t push as hard. I hone that lead pencil and then I can start pushing and writing without breaking it.”
Understandably, the type of material being cut can have different effects on the blade. DoAll, therefore, offers a chart that shows exactly which blades work best depending on the type and size of material being cut. Allen offers an example of an operator cutting 6-in. round. According to the DoAll guide, the primary choice of blade is one that has 2 to 3 tpi. The secondary choice would be a blade with 3 to 4 tpi.
“You always want to make sure you’ve got a minimum of three teeth engaged and a maximum of 25 teeth in the material,” Allen says. “You need to have a minimum of three engaged – there is a lot of weight in the saw head, so if you have one or two teeth engaged and that saw head comes down, you could snap off the teeth.”
On the flip side, if there are too many teeth going through the material at one time, Allen says the gullets will overfill with chips, leading to broken teeth.