The difference in speeds of the cutting tool and the material that the tool is operating on is known as the speed rate. Speed rate is measured in SFPM which stands for Surface Feet Per Minute. Speed Rate of a cutting tool can be controlled by using the variable pulley, fixed pulley and electronic drive. The fact that speed rate of a cutting tool is an important variable in the cutting process makes it necessary for the operator to understand this factor so that he can maximize cutting performance as well as the blade life.
While trying to use the cutting tool at optimum blade speed, the 100-200-300 rule of thumb should be applied. This rule should be known to all operators because it forms the basis of blade speed optimization.
There are few band saw machines which can change speed of the blade. Generally the suggested speed for cutting wood by using a band saw irrespective of the width of the blade or the configuration of teeth is close to 300 SFPM. It can be used at slower saw speeds when non-ferrous materials such as copper, brass, aluminum or thin steel are under the blade.
Since speed gauges of the machines are not very accurate, it is wise to keep checking the blade speed at intervals. For checking speeds up to 600 SFPM, either use the weld mark or mark the band and count the number of times the mark passes through a certain point in one minute. Subsequently, multiply this value by the length of the blade in feet and inches.
Band speed gets restricted by the machinability of the material as well as the heat produced during the cutting process. More heat is generated at high band speeds and on cutting hard materials which results in reduced blade life.
To know whether or not you are running the blade at the right speed, have a look at the shape and color of the chips. They can best indicate whether correct feed rate and speed are being applied or not. The aim is to get tightly curled, thin and warm chips. If you notice the chips turning brown, you are forcing the cutting through the material which is generating too much heat. Blue chips are an indicator of extreme heat which is sure to damage the blade being used.
Band speed must match the type of work being done. If the band speed is in excess, the teeth of the band may dull prematurely. It may also increase the problem in cutting while doing tough jobs. Too slow band speed may give rise to inefficient production and reduced cutting rate resulting in tooth stripping and work spinning.
As a general rule, harder the material, the slower should be the speed and softer the material, the faster should be the speed. Fast speed produces finer finish on the surface being cut.