Just saw it

Using a saw to cut something to length is perhaps the most basic and ancient of manufacturing processes. Copper saws were documented in Egypt, back around 3000 B.C.

While headlines and stories abound about great new technologies, like lasers and high definition plasma cutting, sometimes a band saw is the best solution.

“Band sawing is actually gaining momentum and has not lost its foothold in the market,” says Dave Snyder, business development product specialist at Cosen Saws. “You have steel mills producing larger and larger pieces of metal. Twenty years ago, to see a 24-inch I-beam was rare unless it was manually made. Nowadays, you are looking at milled run beams that are much, much larger—36-inch, 40-inch, going on to 48-inch. So the mills are making these materials...someone has got to somehow cut those down into usable lengths.”

According to the experts, saws are still a preferred option over lasers, plasma or oxy-fuel for large metal. “When you are cutting a beam or something like that, in most cases it is a hand operation. Someone is going in there old style with an oxy fuel torch or a plasma to cut it, but you will still end up with a rough edge,” says Snyder. “I believe that band saws are still the most popular way today to cut material down to specified lengths.”

Cutting material to length, especially tubing, beams, solid bar stock, inexpensively is the saw’s forte. “Band saws in general are much lower cost solutions, and they can cut much thicker pieces of metal,” says Bill Verbrick, national sales manager for Marvel Manufacturing Company. “Both the initial investment and the operating costs are much less. Plasma and laser are common in the plate processing industry and are generally used to cut shapes. Lasers are limited to about 1-inch thick and plasma can cut up to 12-inches thick. A straight cut using a plasma will be faster but causes deformation on the cut surface.”

Saws are not an old crude technology. Not only are they less expensive to acquire and operate, they are very accurate and fast.

There are two types of saws that can be used in the manufacturing process. Like in woodworking, you can have a band saw or a circular saw, also called a cold saw.

The cuts on a cold saw are typically straighter and smoother than from a band saw, and they can be taken to the next step of fabrication whether it is milling or welding. Typically no cleanup is required.

“The main advantage to a circular cold saw verses other types of cutting machines is a circular saw will give you a very accurate/square cut +/– .002 per diameter inch with very minimal burr,” says Jerry Kroetch, president of Scotchman Industries. “By giving the square, burr-free cut in most cases this will eliminate the necessity to deburr the part after it is cut.”

“Automatic cold saws, or circular saws, are gaining popularity in high production environments,” says Snyder. “They have an extremely high cutting rate, accuracy, and good quality finished cuts on the ends. They are gaining popularity, especially when it comes to cutting solid bars in the 1-inch to 6-inch range and even up to 8-inch sizes. They are very efficient as far as productivity, but there is a premium because they are expensive. If you have a requirement where you have a very high production, a cold saw will certainly have the ability to pay for itself. But it has to be in a high production environment for this to make sense.”

High Speed circular saws are usually found in very high production applications where many short length parts are being cut. “High speed circular saws are limited by capacity and typically max out at 9 or 10 inches in diameter,” says Verbrick, who notes that band saws can cut much larger diameters, while the high-speed circular saws cut 3 to 5 times faster than conventional band saws.

Like most equipment designed for production and manufacturing, saws can be automated. “Machines can vary from a manual machine, semi-automatic machines to a fully automatic machine with an in-line bundle loader from ferrous to non-ferrous material cutting,” says Kroetch.

The blade is the thing

It is no wonder that blades are the most crucial part of the saw, and they are the biggest consumable item as well. It is important to know that there is no such thing as a one blade cuts all.

“There is no such thing,” reiterates Snyder. “Customers would certainly like to find that blade one day, and I’m sure blade manufacturers would love to find and make that blade.”

There are many things to consider when selecting the right blade for a job. “The blade teeth have to be tougher and harder than the material being cut,” says Snyder. “Otherwise you are just going to wreck your blade. The pitch of the blade—how many teeth per inch—has to be considered. If I was to cut a piece of 6-inch bar stock, I would probably use a 4 to 6 pitch blade. That allows the saw blade to have gullets that allow the material to build up in there and the material can be evacuated from the teeth. If an operator would go in there with finer toothed blade, the chances are that those gullets would be over-packed with material and it could break the teeth.”

While there are many types of blades to suit all cutting applications, blades do wear out. “The rule of thumb on a circular cold saw blade is you can get a full 8 hours of non-stop production cutting out a blade before it needs to be re-sharpened. Most circular blades can be sharpened 70 to 80 times,” says Kroetch.

“Blade life is measured in square inches of material removed,” adds Verbrick. Material hardness, type of coolant, over feeding, vibration and chip build up all affect the blade life. However, Blade life is completely reliant on the type of material being cut, says Verbrick.

Most circular blades can be resharpened but band saw blades can’t and must be properly discarded when worn out. Snyde explains that you can only bend the blade so many times before they break and if they cost about $50 no one will really sharpen them.

To ensure getting the maximum life out of a saw blade use proper coolant. “In some applications some people still use straight cutting oils,” Snyder says. “Then there are the oil solubles where you mix water with the oil soluble coolant and then of course you have synthetic coolant. And really what the coolant does typically keeps the cut part and the saw blade cool. If the saw blade gets hot then it will get soft it will wreck the teeth very quickly. The coolants keep the work piece and the saw cool so they can maintain the proper cutting rates.”

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