Tooth pitch, which is how many teeth are in the blade per inch, is an important consideration in band saw blade selection. PHOTO courtesy Cosen Saws.
SHOP: Blade teeth are available in several shapes and settings, which can be somewhat confusing. What are the most important things to consider in deciding which tooth size and tooth setting is the best option for a particular application?
CHIBE: With tooth settings, one set on most blades is the standard offered from most blade manufacturers. The other option offered is an extra heavy-set blade. The reason you would pick an extra heavy-set blade is to help eliminate pinching problems with some materials. When you cut through materials that pinch, they squeeze back and literally lock up blades in the material and you have to cut them out with a torch. So what was designed at one point is to go with an extra heavy set (.100” set) and what that did is open up a larger kerf so when the material squeezed back it couldn’t squeeze back enough to lock the blade up to into the material.
Another limiting factor when you’re cutting is gullet capacity. The most important thing is to get the proper tooth pitch. That’s the whole name of the game. Usually when you’re looking at tooth pitch, which is how many teeth are in the blade per inch, that’s where you would take into consider the cross section of the material you’re cutting. A lot of the saw blade manufacturers will have a tooth selection chart in their saw blade catalogues. What they’re trying to do is get you the right edge material and tooth pitch determined by the material cross section.
More from Russell J Chibe:
There is a rule of thumb we use in band sawing: It’s called “Three. Six. Twelve. Twenty-Four.” Those four numbers tell you everything you need to know. Starting from the outsides, the Number Three, you never want less than three teeth in the work at one time. The Number 24 on the other end, you never want more than 24 teeth in the work at one time. With 24 teeth in the work at one time or greater, you will be running out of gullet capacity. That gullet is going to be full before the tooth ever passes out of the work. In regards to three teeth, you never want all of the cutting force to be less than three teeth or you’re going to be in trouble. That’s a lot of force and you’re probably going to snap a tip off. The two middle numbers – six and twelve – that’s the optimum. That’s what we are shooting for, getting six to twelve teeth in the work at one time and you should be in pretty good shape. That’s the sweet spot. Now that’s not saying you’re always going to get there.
Most everything on the market today is varied pitch (tooth design) and I would recommend people go with a varied pitch. You still have the option of getting a straight raker pitch, which offers the same number of teeth per inch. But we found out through the years that you really want to go more with a varied pitch, which would be like a 2-3, a 3-4, a 4-6, or a 5-8 pitched blade. What that’s saying is that for every inch of material on the blade you’re going to have, for example if it was a 2-3 pitch, you’re going to have between two and three teeth on the blade for every one inch and the number of teeth varies as you’re going through the blade. The reason for that is that it helps breaks up harmonic vibration. When you go with a straight raker pitch, you developed a harmonic wave which can lessen the life of your blade. When you go with a varied pitch, it helps eliminate some of that squeal you hear when you’re cutting. It eliminates the vibration and helps to eliminate the harmonics (noise). When you hear a blade squealing really loud, that’s harmonic problems that you’re having. Heat and vibration are the things that help destroy a bandsaw blade. They’re very, very destructive to a blade. If we can eliminate some of that it can help lengthen blade life as well as improve the operator’s working conditions because they don’t have to hear that ear piercing noise. While its not possible to eliminate all noise, we can help to reduce it. In the case of cutting very hard materials, you’re usually going to get some sort of a squeal when cutting them and that’s just the nature of the beast.
Russell J. Chibe is a regional sales manager with Cosen Saws, North America.