In another post, a reader asked why a wood-cutting circular saw cannot be used on metal. Shown above is a metal-cutting circular saw, Milwaukee’s new M18 Fuel model.
In his comment, Ryan asked:
I’m new to all this and recently purchased a Dewalt 60V DCS575. Just wondering why you are not supposed to cut metal with this saw?
I’ve heard a number of good-sounding possible reasons over the years, many of which make sense. For example, someone might say that the guard isn’t designed to protect users from hot metal sparks and chips, or that the shoe isn’t optimized for use on metal materials, or that the internal components aren’t properly protected from metal chips or dust.
While all of these things could be true, we also have to consider cutting speeds. Wood-cutting circular saws work a lot faster than metal-cutting saws.
Let’s look at 2 saws – Milwaukee’s new M18 Fuel brushless metal-cutting circular saw, and their full-sized M18 Fuel brushless wood-cutting circular saw.
M18 Metal-Cutting Saw: 2782
M18 Wood-Cutting Saw: 2731
The metal-cutting saw blade has a 5-3/8″ to 5-7/8″ blade size and spins at 3,900 RPM. Let’s consider the 5-3/8″ blade size for the purpose of this discussion.
A 5-3/8″ blade has a circumference of 16.9″. Given a rotational speed of 3,900 RPM, the linear speed will be comparable to 65,910 inches per minute, or 91.5 feet per second.
The wood-cutting circular saw has a 7-1/4″ blade size, spinning at 5,000 RPM.
A 7-1/4″ blade has a circumference of 22.8″. Given a rotational speed of 5,000 RPM, the linear speed will be comparable to 114,000 inches per minute, or 158 feet per second.
91.5 feet per second for the metal-cutting saw and 158 feet per second for the wood-cutting saw is a very big difference.
I know a lot of users use wood-cutting circular saws for cutting light duty metal with the right blade.
But when it comes to cutting a lot of the types of materials you would use a metal-cutting circular saw on, such as angle iron, that wood-cutting circular saw blade is going to be spinning way too fast and might not have the torque needed for fast or safe performance.
And all that is ignoring potential safety concerns in using a tool designed for cutting wood to cut metal.
Notice, for example, that a wood-cutting circular saw often has a dust ejection port that channels sawdust out the side. Metal-cutting saws do not. I can’t seem to find a good answer, at least not quickly, but I’d guess that OSHA regulations would disqualify such wood-cutting circular saws for use on metal materials.
Are there any other reasons why one shouldn’t use a wood circular saw in place of one designed for cutting metal?