Cutting Metal on a Miter Saw

Today, I tried out a couple metal-cutting blades on my not-designed-to-cut-metal chop saw. I neither expect to nor recommend doing this often. My online searches resulted in the general consensus that it's a bad idea for the following reasons

• metal chop saws are designed with lower RPM and higher torque, meaning that wood chop saws may have a tendency to burn out quickly if used for cutting metal
• metal chop saws are designed with enclosed motors to prevent the fine dust of metal cutting to get into the motor
• if you cut metal where you cut wood, there's a good chance of igniting a sawdust pile with an errant spark
• metal chop saws have built in clamping systems

Here are some links if you're interested:

• https://home.howstuffworks.com/what-type-of-circular-saw-blade-do-i-need-to-cut-metal.htm?fbclid=IwAR22BJeRV6iWMhz8FXtvIYNu2PZrE9yU3L3DSRe5Lfub5BueTLWXcnPrMNM
• https://forum.millerwelds.com/forum/welding-discussions/7868-chop-saw-versus-miter-saw-with-metal-blade
• https://www.finehomebuilding.com/2012/08/22/circular-saws-sidewinder-vs-worm-drive
• https://weldingweb.com/showthread.php?34466-Can-my-Mitre-saw-be-used-as-a-Metal-Cutting-Saw
• https://youtu.be/nXLW7Wew6Fk
• https://www.youtube.com/watch?v=X7VL4NIpWmM
• https://www.youtube.com/watch?v=UGvexh3-HL8
• https://www.youtube.com/watch?v=Y9oTzK1E0c8

With these considerations in mind, I still elected to give it a try. Notably, if this is something that I begin to do with greater frequency, I'll find another option. For infrequent use, though, it seems to function just fine.

On the way home the other day, I picked up two 10" blades at Lowe's: an abrasive blade and a carbide-toothed steel blade for cutting metal. Lowe's was my third stop, and the steel blade was not cheap, but it's what I was looking for.

I did some more poking around online and learned of the difficulties associated with the abrasive blades, particularly: excessive heat build-up, and a lot of mess. But, considering it was a much cheaper blade (~$6 rather than ~$70), I was hoping it would be good enough. I did keep the receipt so's to be able to return one or both of them.

Before getting started, I verified that the RPM on my miter saw was less than the rated RPM on both purchased blades.

Note the "4900 RPM" rating in the lower-right corner.

I cleaned up sawdust in the area. Then, using some spare sheet metal I had lying around, I built a small shield to install behind the blade and arrest (or at least slow down) the bulk of the sparks. It fit nicely at the back of the table on the saw.

NOTE / spoiler alert: I didn't actually start taking photos until after I'd changed blades.

When I got around to using the carbide-tipped blade, I installed it with the labels facing to the right, which I would normally consider backwards. As you can see, though, this ensured that it turned in the correct direction.

I got the abrasive blade installed (might as well start with the cheap one!), though -- to my later chagrin -- did not measure it before I began using it. After a couple cuts, I had to concur with what I'd read online: lots of heat and lots of sparks. I had my mini IR thermometer handy and measured up to 170˚F in today's heaviest workpiece (1/4" steel, 1.5" wide). The sheet metal guard I'd made got up to 130˚F. Even in the test pieces I cut (1/16" rod and 1/16" tube), I don't think anything was less than 120˚F after the finished cut.

In hope of reining in the fire hazard, I bit the bullet and opened up the package for the carbide-toothed steel blade and installed it.

Oh, what a difference! Instead of grinding its way through a hunk of metal, flinging a fine pyroclastic powder all over the place, the saw now made its way easily through each piece of metal I asked it to cut. There were certainly still sparks, but way fewer of them and not for nearly the duration. Cuts were quick and easy, with nearly no heat build up on the blade, in the workpiece, or on the deck. Workpieces started at ~65˚F and never got above the mid-80s. Additionally, cuts were clean, with none of the slop that the abrasive wheel left behind.

Abrasive cut-off wheel	Steel blade

1/4" Steel (1.5" wide) Left: cut with steel blade; Right: cut with abrasive cut-off wheel

So, overall, I'm pleased. After the test cuts, I made 16 cuts through 1/4" x 1.5" steel. This will make practice pieces for some welding. As I was cleaning up the cuts that the abrasive wheel had made, I noticed discoloration due to overheating left behind by the abrasive wheel. Glad to have the steel blade.

Note: I did end up touching up all of these small pieces on the grinder, but the only ones that had dangling shreds of metal were those cut using the abrasive cut-off wheel.

Also, I definitely had on the wrong gloves for this task. They didn't have any holes in them when I started...