The best way to establish blade speed for cutting materials

The best way to establish blade speed for cutting materials

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. The speed Rate of a cutting tool can be controlled by using the variable pulley, fixed pulley, and electronic drive. The fact that the 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.

Let us see what does the 100-200-300 rule mean?

  • For hard materials, set 100 SFPM as the starting blade speed so that it runs at 98.42 feet/min.
  • For medium materials, set the blade starting speed at 200 SFPM so that it runs at 196.85 feet/min.
  • For soft materials, set the starting blade speed at 300 SFPM which will run it at 328.08 feet/min.

Note: The SFPM rates mentioned are an average of the speeds recommended by various manufacturers. Speeds recommended by various manufacturers may vary from one manufacturer to another.

There are few band saw machines that can change the 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 the 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 uses 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 result 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 the 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 of 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, the harder the material, the slower should be the speed and the softer the material, the faster should be the speed. Fast speed produces a finer finish on the surface being cut.