Band or circular

April 1, 2002
Most shops make one classic mistake when it comes to selecting a saw.

Most shops make one classic mistake when it comes to selecting a saw.

For jobshops, a small circular saw, such as Kaltenbach's KKS 400 E, and a larger bandsaw like the company's KB 360 G is an ideal combination.

Kaltenbach's KBR series showcases the company's latest bandsawing innovations.

The biggest mistake shops make when selecting a saw is choosing the most inexpensive machine with the largest capacity. That's because they tend to consider every single part they've ever cut and then attempt to purchase a saw that handles it all. In reality, shops should focus on the bulk of the parts they cut 98% of the time and go with the highest quality saw they can afford with enough capacity. Depending on these jobs, the right saw may be either a bandsaw, circular saw, or both.

For many jobshops, the ideal setup is a combination of a small circular saw and a larger bandsaw. The circular saw cuts stock sizes up to 6 in. and complicated miters, while the bandsaw handles the bigger stuff. Unfortunately, not all jobshops think in terms of two saws and, therefore, continue to purchase either a circular saw or bandsaw.

According to David McCorry, president of Kaltenbach in Columbus, Ind., most shops choose a circular saw for surface finish or squareness reasons. "If money were no object, everyone would buy a circular saw because they do a better job," he says. But there are drawbacks. For example, a circular saw can't cut big billets of titanium, but bandsaws can.

Bandsaws also provide more flexibility, cutting virtually any material — aluminum one minute and Inconel the next. A circular saw, on the other hand, can't switch between materials because machine specifications differ for each material type. "Even tool steels run at completely different speeds than aluminum on a circular saw," says McCorry. "A steel circular saw cuts aluminum, but at slower speeds and with less-than-perfect surface finishes and squareness. This is why Kaltenbach offers circular saws specifically for certain materials."

At first glance, Kaltenbach circular saws appear the same, but under the skin they are completely different. The KKS 400 E steel machine, for example, runs exclusively on gearboxes for heavy feedrates, while the company's SKL models for aluminum operate with a belt-and-pulley system for high speeds and use tungsten-carbide blades. The aluminum models also feed pneumatically, but the steel versions require hydraulics for adequate clamping during high-force steel cutting.

"There's no way a bandsaw can achieve the same surface finishes or speeds of a circular saw," says McCorry. Circular blades run 12,000 to 20,000 sfm and produce finishes that, in some applications, require no secondary operations.

Maximum material size to be cut usually determines whether to buy a bandsaw or circular saw. If a shop wants to cut up to 6 in., says Mc-Corry, there is really no difference between the two types of saws. But once material size climbs to 10 in. and above, there's a huge difference in price — so much so that Kaltenbach stopped making a tungsten-carbide-tipped circular saw for 7-in. material because the company's band-saw easily handles that size and costs 25% less.

Along with material type and size, shops should consider miter cutting. If the material is small enough, the ideal saw for miter cutting is a circular because it sets up quickly and easily and provides a much cleaner cut. For example, setting up the KKS 400 E for a 0° to 45° miter takes seconds. Operators unlock the table, rotate it, and re-lock. The material and machine stay in line while just the table swivels.

On a bandsaw, the same miter cut is possible, but setup takes longer because the saw's whole top half has to turn. Kaltenbach's KB 360 G bandsaw, for example, turns in one direction for miter cuts, which keeps its design simple and cost low. For opposing miter cuts, shops simply flip material over, which takes less time than turning the bandsaw a second time.

If a shop cuts a little of everything, says McCorry, it should choose a bandsaw. "It cuts almost anything, but shops must accept that it won't cut any one thing extremely well."

The main criterion when selecting a bandsaw is blade size and motor power. Most well-built machines have a high power-to-bandsize ratio with power to spare. "Any manufacturer can make a bandsaw that cuts 16-in.-thick billets," says McCorry. "The question is whether or not the machine can actually handle the rigors of such a cut."

Bandsaws can't be made beefy enough to endure the punishing treatment they receive. Shops don't often regard these saws as machine tools but as utility pieces of equipment, says McCorry. And as such, they are not replaced on a regular basis, so shops should purchase the best bandsaw they can afford.

Showcasing Kaltenbach's latest bandsaw technology is the company's KBR series of saws. These double-column machines feature such advancements as linear guides, frequencyregulated drives, separate torque suspension (STS) bandwheel mounting, and a CNC with special software package.

The linear guides are in the saw's frame, vises, material-feed gripper, and sawband guide. Besides accuracy, they provide maintenance-free operation, eliminate stick/slip during movement, and make for a more compact machine overall. A slimmer machine, in terms of material direction, is more accessible for operators.

Frequency-controlled motors on the KBRs' sawband drives provide infinitely adjustable cutting speeds. And conical spur gears deliver quiet operation and long drive life.

For vibration-free running and extended blade life, Kaltenbach equips the saws with STS. Basically, the design separates the band-tension load from the gearbox. A large double-tapered roller bearing shoulders all the tension, not the gearbox.

Having CNC, the KBR machines are completely programmable and can be downloaded to. A software package, called Omni Cut, complements the machine control and reduces the amount of operator intervention needed to program different stock sizes and complex cuts. Shops determine all the parts needed from all the different raw materials. And if so desired, the machine sorts parts, or jobs, according to those that can be cut from the same material.

Each component to be cut has its own part number, which is used to call up the job. The machine compares all the jobs called up and nests them together according to material. But users can sort jobs any way they see fit, and their choices, says McCorry, are endless. The software lets machines operate fully automatically or provides various degrees of over-ride capability. It also permits material-oriented cutting or parts -oriented cutting.