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COLD SAW vs. BAND SAW By Bob Hoffmann
Cold saws are metal cutting circular saws that use high-speed steel and carbide tipped blades. It is a milling process that cuts cleanly and quickly with a minimum burr. Many styles of cold saws exist from small manual machines for handrails and small fabricators to carbide saws for production cutting of solid bar stock to large structural saws with capacities of I beams up to 20" x 48". These saws can be configured as manual, semi automatic, and fully automatic. Manual machines require the operator to return the saw at the end of the cut. Semi automatic saws clamp, advance the saw, and return automatically. Fully automatic saws advance the material, complete the cut, and return. Some saws also offer automatic mitering. The advantage of a cold saw over a band saw is the speed and accuracy of the cut and the minimal cost per cut. So you might ask how a circular machine cuts faster. It is simply a matter of mechanical strength. The larger, wider, stronger circular blade absorbs much higher cutting forces without mechanical failure. A circular blade runs optimally at feed rates that would strip the teeth off any band saw. This greater intrinsic strength allows the circular saw to cut slower peripheral speeds, while maintaining a chip load many times greater than that mechanically possible with a band saw. A slower peripheral speed generates less heat for a longer blade life. Of course, the machine running the blade also must be designed and built to endure the powerful cutting forces generated by a slow-running blade making a very heavy and intermittent cut. Circular cuts also exhibit less runout and better surface finish. In addition, runout does not increase as blade life diminishes. Trennjaeger cold saws use a blade guide to hold straightness over long cut lengths. Lower cost per cut is accomplished with the ability to resharpen the blades. A rule of thumb is 2000 square inches of material cut between sharpening. High speed steel blades can be resharpened for $1 to $1.50 per diametric inch and segmental blades can be repaired with new segments if damaged and resharpened. It is very important when using a cold saw to cut stainless steel that the blade will run at a speed giving 50 ft/min speed at the cut. For a 14" diameter saw blade the saw speed should be 25 rpm. Higher speeds will greatly reduce blade life and cause blade breakage. New and used cold saws are available for a variety of applications for production metal cutting in fabrication shops and other production environments. Excerpts from August 2004 issue of The Fabricator
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January 2018
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