First, there is some discussion on cutting steel on this thread. In case some haven’t seen it, I’m starting this thread just for the subject…cutting steel.
I was advised for and against using a metal blade in my carpentry miter saw. I chose to try it and this is my experience. You can read it and use it any way you want.
1. It does work. I had some problems with slower cutting on either the top or bottom surface of the tubular steel. It was suggested that A) steel has grain and I may be cutting against it. B) One side may be the weld side and is harder. Anyway, starting the cut through a flat surface is much harder to do than cutting from the edge.. Once I got through the flat side, cutting on down to the bottom went quickly and then slow through the flat bottom. I tried, with success, using a 3” air cutter to start the cut through the corners and scoring along the cut line, then using the miter saw to finish the cut. That worked better and the miter cut went through the top quicker. Using a cutoff blade in a grinder would probably work much better. I had one cut that was off from top to bottom, but I solved that problem by clamping the piece to the saw, both to the bottom of the surface and another co the fence, making sure the piece was flat on both bottom and to the fence, and couldn’t move. That got me a perfect cut. A little clean up with the grinder, and then beveling the edges for the weld bead, and I was done...And, I still have all of my fingers.
2. Did it hurt the miter saw? No. I removed the dust bag, and the plastic insert and made deflectors from pieces of flashing and put them behind the cutting area to protect the plastic angle guide for compound miter cuts. I held the blade guard up out of the way when cutting.
3. Were there any other problems? Yes. The grit got into the circular track where the blade assembly rotates to cut angles. After making eight 45 degree cuts, I tried to move the blade assembly back to 0 degrees, and it wouldn’t budge. I sprayed WD-40 in the cracks on top and bottom and finally got it to move. So, I removed the cutting assembly, then the pivot track and cleaned everything with WD-40 and mineral spirits. I didn’t put any lubricant on the track when I was done, as I thought it would mix with sawdust and clog up again. After cleaning and reassembling, it rotated smoothly again. If I use the miter saw again for metal, I'll put duct tape over all of the cracks to prevent grit from getting in.
4. Did I save time using the miter saw? Under the circumstances, I don’t think so. I used it because I thought I couldn’t cut an accurate miter with the grinder and cutoff blade. After using my little 3” cutoff tool, I now think I could cut miter cuts with the grinder. And, I now think using the grinder would have been faster, considering the hour I spent taking my miter saw apart and putting it back together. It would take careful marking and following the lines closely. From my experience, I won't even attempt using the miter saw to cut flat plate. That's a job for the grinder with a cutoff blade. I may even use my old circular saw (it's all metal) that has a metal blade in it. I suppose I could use my table saw, but I don't think I'll try it.
Today, I will buy a cutoff blade for my 4 ½” grinder and see how that cuts both straight and miter cuts. I’ll add an update on that, probably on Monday, after I’ve tried it.
A final note. I DID wear long sleeves, a cap, and hearing and eye protection. I forgot the cap once or twice, but after a spark or two landed on my buzz cut, I put it on.