SHOP: Blades are made from a variety of materials. When are bimetal blades the best option? What’s the upper limit of the operating temperatures it can withstand and hardness levels they can cut?
GORDON: The carbon blade was the first band saw blade. Everybody cut everything with a carbon blade. However, when bimetal came out in the 60s, it pretty much took over the metal sawing market. Today, it is rare to find anyone cutting metal with a carbon blade. If you’re cutting steel of any kind, bimetal is typically the first choice. If you get into some challenging alloys, you may need to bump up to carbide tipped, but generally everyone cutting steel is using bimetal these days.
Bimetal blades typically have 67/69 Rockwell C tooth hardness and so can be used in materials up to 40/45 Rockwell C. That’s not to say they won’t cut a bit above that, but then the cost per cut goes way up. For example, if you’re cutting Inconel and trying it with a bimetal blade, will you cut it? Probably, but it may take a long time and it will likely wear out the blade . There are a lot of materials you can cut well with bimetal blades such as general steels, structural steels and carbon steels, and even some stainless steels and titanium. But they will not cut everything well. Once you get above 45 Rockwell C you need to start thinking about carbide tipped blades, because carbide itself can go up to 50+ Rockwell with a positive rake. In many cases, there are shops cutting a wide range of materials, everything from aluminum to stainless steel and all the carbons in between. But changing a blade from bimetal to carbide may not make sense if it is just for a few cuts.
SHOP: When should a carbide-tipped blade be considered the best option? What advantages does it provide? What’s the upper limit of the operating temperatures it can withstand and hardness levels it can cut?
GORDON: Carbide blades, which have approximately 100 Rockwell C tooth hardness, offer several advantages including long life and fast cutting.. The disadvantage is they don’t like vibration. So, if you are trying to decide whether to go up to a carbide-tipped blade, there are decisions to consider. Do you have a saw that can handle a carbide blade? You can put a carbide blade on pretty much any saw that will take the width of it.. But if you have a 40-year-old saw that is shaking and rattling, it’s probably not going to work very well. In that instance, the carbide blade is going to cost you significantly more than the bimetal, and your machine is going to be what tears up the blade (even more so than the material). Now, if you were in the market for a saw machine, and you are going to be primarily cutting hard materials, there are saws that are specifically designed for carbide. They are heavyweight, produce no vibration, and can run at much faster speeds – all the things that carbide likes. For production operations, the decision to use carbide is made because they are not getting enough pieces on the floor. The bimetal blade may not be cutting fast enough, or blade life is not good. . Since changing blades takes time, carbide-tipped can last longer and reduce blade changes.
Jay K Gordon is the North America sales manager, saws and hand tools, with The L.S. Starrett Company
