Advantages and Challenges of a Cold Cut Chopsaw
Kevin got a lot of questions from his last how-to video about his chopsaw - a lot of guys hadn't seen that kind of cold cut saw.
Most people are familiar with an abrasive blade. The problem with abrasive blades is that, if you push too hard when cutting with them, they flex, which can cause a curve in your cut instead of the perfectly straight cut you want.
His chopsaw, which is sometimes called a "cold cut saw" or "dry cut saw," has a metal blade. He shows the teeth on a metal blade that just came back from the saw sharpener (it still has the protective wax coating on it). They put a little different pitch on the blade - a little different angle on the top and on the sides to help cut the metal better. The blade he is holding in his hand is a 102-tooth blade, while the one on the chopsaw is a 79-tooth blade. The one with 102 teeth is for harder metals, while the 79-tooth blade is for softer metals like aluminum. These metal blades cut much cleaner and straighter than the abrasive blades, but the blades run from $80 to more than $200. But you can sharpen each blade many times, and saw sharpening companies can actually weld new teeth onto a blade if you hit something hard or break off a tooth.
With the abrasive blades, you have to just throw them away, although Kevin uses them on his 7" and 4-1/2" angle grinders until they're too small to use.
The saws themselves are different, too. The chopsaw that uses metal blades has a much bigger but slower motor. So you can't buy an abrasive blade chopsaw and put a metal blade on it, because it won't turn slowly enough [NOTE: NOT "FAST ENOUGH" AS IN THE VIDEO] - you'll just burn up the motor.
Kevin has already used his square to check the chopsaw's backstop to make sure it is 90 degrees to the blade. The saw doesn't have a very accurate way to line up the blade, so you can get a few degrees of variation, but using the square can compensate for that. Next, Kevin clamps down the pipe. You want to just snug it up, then give it a 1/8 turn or so. If you over-torque it, you can push the backstop up away from the table and bend the table so your backstop is at an angle. Again, there goes your straight cut.
Then Kevin puts on his safety glasses and ear protection and cuts off the end of the pipe. He points out that he just used the weight of his hand to guide the chopsaw down - he wasn't pushing hard or applying much downward pressure it at all. If you see too many sparks, you know you are putting too much pressure on the blade, which just dulls it - or indicates it is dull. Using the cold cut chopsaw correctly, you get a smooth, clean cut on both sides. They're so clean, you could put the two pieces back together and weld them (some pieces you want to chamfer, or bevel, though).
The metal-blade saw is a little slower and probably a little louder than the abrasive-blade saw, but it's a much cleaner, straighter cut. The kerf of the cut is about the same, but the cleaner cut is well worth it.
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