The relationship between Speed and Feed Rates is vital to the proper function of a bandsaw and requires a saw operator’s full attention or the bandsaw will fail to perform as expected.
Speed Rate
A saw blade’s speed is defined as the distance in feet that the blade travels per minute: a measurement of S.F.P. M. or Surface Foot Per Minute.
In order to achieve proper blade speed, the SFPM must be optimum for the application. The drive belts cannot be slipping under the load being machined, and the tachometer needs to be checked often in order to assure that the proper RPM’s are being maintained.
RPM maintenance includes the use of a tachometer, but without one, there is a simple method to assure that the RPM’s are being maintained, but it only works for RPM’s that are set up to 600 SFPM.
- Use the weld as a reference point or make a dark line across the blade with a marker
- Start the saw and count the number of times that the mark comes around in one (1) minute
- Multiply that number by the length of the blade in feet and inches (12’ 6” blade — the mark or weld comes around 14 times in one (1) minute — 12.5 x 14 = 175 SFPM)
The correct Blade Speed used for the material being cut. Items that influence speed selection include:
- Material Machine-ability Rating – the lower the rating percentage, the slower the band saw speed
- Blade Selection – The cutting edge of the blade will determine the blade speed. H.E.M.B. (Hard Edge) = the slowest cutting — Carbide = the fastest cutting
- Cutting Noise and Vibration – If either are present, the speed must be decreased — especially if blade life is important to the cutting operation.
- Coolant and Cutting Fluid – If the coolant is adequate, use the standard cutting speed charts recommendations. If the cut is to be made dry, reduce the speed by 40% to 50%
The experienced and professional bandsaw operator must be aware of the recommended blade speeds in order to maximize the efficiency required for production requirements.
Adjustments made to the speed and feed rates are as follows:
- Reduce band speed by 30% – 50% if using a saw blade without cutting fluid
- Reduce the cutting rate by 25% for structural’s
- Reduce the cutting rate by 50% for pipe
- Reduce the cutting rate by 65% for tubing
To calculate the cutting rate, divide the area being cut by the cutting time. To calculate the cutting time, divide the area by the cutting rate.
What is the relationship between feed, speed, and tooth pitch? (Please note that only one (1) variable should be changed at a time).
- INCREASE THE WORK SIZE to decrease tooth penetration
- REDUCE THE TOOTH PITCH to increase tooth penetration
- INCREASE THE TOOTH PITCH to decrease tooth penetration
- REDUCE THE BLADE SPEED to increase tooth penetration
- INCREASE THE BLADE SPEED to decrease tooth penetration
For example if your work piece is a 1″ solid round and you set the machine to 100 pounds of feed pressure on your blade; if you have a 2 T.P.I. blade, that would equal 50 pounds per tooth of penetration. If you have a 10 T.P.I. blade, that would equal 10 pounds per tooth penetration.
