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Saws for Metal Cuttings

Choosing the right saw blade for cutting different types of metal

Tenryu Dec18 2

On metal construction job sites, there are a variety of metal building materials to be cut with different saws. Materials such as studs, tubing, roofing/siding panels and foam insulated panels are commonly found at these job sites. Unlike snips, reciprocating saws, portable band saws, nibblers and shears, cutting with a circular saw is handy, fast and easy for cutting straight without deforming the material. Inferior quality of cutting easily damages the material to cause warranty concerns.

For maintaining warranty, some material manufacturers specify the tooling brand or the product name for cutting provided in their installation manuals. Contractors should check the manual or contact the material manufacturer before cutting.

However, in reality, there is no guarantee to find what they need to use from customer service, before a cutting project. In many cases, a material manufacturer’s recommendation is too generic for contractors to find the right tool with confidence. What follows is information on circular saw metal cutting.

Ferrous Metal (Mild Steel)

For safe and efficient cutting, secure the material flat and immovable. For panel or flat stock cutting, use a guide rail or straight edge of plywood for sawing straight along to minimize the gap in the cutting path.

There are two types of circular saws. One is designed for cutting wood at a high RPM speed; this type is more popular than the other. For making bevel cutting, there is a wide opening on the base, and inside the cover. It is easy to see the line marked on the material at cutting. For mechanical construction, this type of circular saw should be limited to cutting only thin-gauge stock, from 29 gauge up to 1/8-inch wall thickness.

For cutting flat sheet stock, use a circular saw blade with lots of teeth, such as a 7 1/4-inch diameter blade with 56 to 70 teeth and a negative rake angle. Make sure to cut the panel side to side, avoiding plunge cutting. Plunge cutting produces a lot of heat and makes the teeth wear out quickly.

This flat stock cutting blade is not suitable for cutting shaped sheet steel panels. For cutting shaped roofing/siding panels, foam insulated panels, structural studs, channels or tracks, use a 7 1/4-inch diameter blade with medium tooth count, such as 48 teeth and neutral rake angle.

Even though general-purpose steel cutting blades are designed for cutting up to 1/8-inch wall thickness, cutting with this regular RPM circular saw will not maintain the saw blade’s life for long. If you often cut 1/8-inch or thicker materials, such as threaded rods, 12-to 16-gauge studs, decking, strut or plate (heavier than 1/16-inch), the other type of circular saw, specially designed for cutting steel, should perform more adequately, reducing heat generation of cutting to extend the blade’s life.

Non-Ferrous Metal

Non-ferrous metals, including aluminum, copper and bronze, are softer than steel, but harder than wood. A slight movement of the material during cutting may cause a high impact to the teeth, resulting in jamming or tooth damage. The sawdust can stick to the carbide teeth and the plate. Once this starts, the gullet quickly fills with sawdust, causing a high pressure between the teeth until they possibly break.

To prevent this, it is very important for thematerial to be firmly clamped (with a mechanical device), and apply sufficient lubricating oil or wax to the teeth and the material. Regular RPM speed woodworking circular saws are adequate to use, and more efficient to extract sawdust. Typically, non-ferrous building materials are thin stock, such as soffit, sheet, or frame. For cutting the thinner materials without deforming, more teeth on the saw blade is recommended.

The distance between the teeth should be approximately 5/16 inch to 3/8 inch, as seen on 7 1/4-inch diameter blade with 60 teeth, and a neutral or negative rake angle. Do not use a steel-cutting saw blade for cutting non-ferrous metals. The designs are totally different, and a steel-cutting blade will not last long when cutting non-ferrous metals.

Keiji Iida is national sales manager at Tenryu America Inc., Hebron, Ky. To learn more, visit www.tenryu.com or email kiida@tenryu.com.