Why do abrasive cutoff blades stop cutting after a couple cuts?

Answer 1

I have had this problem. As the blade wears the diameter decreases, lowering the actual feet per second the blade is cutting. Even though the rpms stay the same. To add to the problem the material and the blade tend to work harden slowing the process even more. If you are doing allot of cutting you may have to upgrade your sawing machinery.

I thought of the diameter/speed issue and checked the diameter of the blade. They were within 1/4" diameter of new so I figured it had to be somerthing else. I built an entire 4 place aircraft fuselage with the saw and never had a problem cutting thin-walled 4130 tubing. Cutting thicker stuff, like 2 x 4 x 3/16" rectangular tube takes longer and get quite a bit hotter. Anyway, tried running the blade backwards and it seemed to work a little better but then I figured it out.

I think the nooks in the abrasive composite get filled with molten steel when the blade gets hot cutting thicker material and taking a longer time to do it. I took a "dull" blade and laid it flat on the tool rest of my bench grinder. Then I ground off the very outside edge of the blade, removing the embedded steel. I say that with some confidence since there are red sparks, indicating iron. Flipped the blade over and went around running it across the grinder wheel. Works like new.