Most metal sawing operations can become cost-effective with the use of the proper mix of coolant on a well maintained bandsaw.
Proper coolant usage improves cutting rates by balancing the combination of cooling and lubrication of the blade. Quality coolant improves the cut finish and can extend blade life by as much as 20%.
The sawing operation generates extreme heat when chips are sheared from the material and from the friction of metal-to-metal contact at high speeds. Using a coolant — flood-applied or mist — reduces the heat generated by these sources.
Coolant also prevents metal chips from welding to the tooth face and altering the chip removal capacity of the band gullets, dramatically affecting blade performance.
Machine Considerations
Some saws are equipped with a flood-applied coolant delivery system that captures and returns the coolant to a reservoir. A saw without a coolant delivery system should only be used to saw easily machined materials such as mild steel and aluminum.
On a vertical or horizontal saw, a misting system can be used to provide the lubricity needed to reduce frictional heat. A misting system does not provide evaporation cooling of the blade or the work piece, so band speeds should be reduced by 15 – 20%.
Dry cutting requires a band speed of half the normally recommended speed when a coolant is used.
For small saws that are not equipped with a coolant collection table, a small, relatively inexpensive spray misting system may pay for itself over a short period of time.
Structural shape sawing often results in a high coolant loss during flood system application. Fortunately, angle, channel, and tubing offer a small cross section to a blade, so very little heat is trapped.
Consequently, a misting system is effective at providing frictional heat-reducing lubricity to the blade.
How it Works
The basic mist uses the Venturi (reduction in fluid pressure) principle of operation.
When air is introduced to a typical unit, (like the M-122 MagnaMist) and the air valve is open, it passes completely through and is released at the nozzle tip.
The air stream forms a Venturi, creating suction that draws coolant from a reservoir to the coolant port, where it joins the air to form a mist spray.
The compressed air passing through the valve body and to the nozzle tip, creating a vacuum in the liquid line and drawing coolant from the tank.
The coolant is instantly vaporized and forms a conical mist pattern. At the same time, the compressed air expands, absorbing the heat that surrounds the tool and work piece.
The force of the spray is regulated by adjusting the air valve to control both air volume and velocity. To adjust the coolant volume, turn the nozzle housing.
The end result is a cooling effect as well as lubrication.
