Cutting tubes is more difficult than sawing solid bars. It is because the band saw blade is performing two types of cuts. The saw blade is cutting solid as it hits the workpiece. When the saw blade starts to enter the inner wall of the hollow part, it is now cutting two thin solids with a space in between them (interrupted cut).
Blade variables and band saw settings have to be selected very carefully to provide the best result in cutting tubes .Toothpitch or number of teeth per inch, is a very important variable in sawing tubes because the number of teeth engaged with the material determines both blade performance and durability.
If only few teeth are in contact with the workpiece, this can lead to tooth strippage from the blade, bent, or prematurely dulled. When too many teeth are engaged, the gullet will soon be filled and will result to crooked cut if the blades does not break first.
Recommended minimum of 3 teeth and no more than 24 is always be in contact with the material. Within that range, the pressure on each tooth is enough to ensure penetration of the material, shock levels are tolerable, and there are enough gullets to carry away the chips produced by cutting.
Pitch can be either constant or variable (multiple configuration). Blades that has multiple configuration of teeth varies tooth spacing and are designated by two numbers. The coarsest single-pitch equivalent, and the finest single-pitch equivalent. A band saw blade that has 5-8 pitch has teeth spacing that varies between 5 and 8 teeth per inch. Vibration is reduced and sawing rhythms are broken up by varying the tooth spacing between fine and coarse.
For example: For a 5.25-inch wall thickness, the minimum pitch for effective sawing would be an 8, so a multipitch blade around 6 to 10 pitch would be chosen as the most effective.