How to Improve the Quality of Cuts Made With a Metal Band Saw
The quality of cuts made with a metal band saw depends on several factors. Some are obvious, but others may be overlooked. These include: the blade, down feed rate and pressure, workpiece support, and machine maintenance.
To achieve accurate cuts, the blade must track correctly on the wheels. This ensures proper cutting and reduces down time for repairs.
Coolant System
Using a metal band saw without a proper coolant system is dangerous and can damage the machine. The cutting process generates extreme heat from friction between the blade and material at high speeds, as well as from shear forces when the chips are released. Coolant—flood-applied or misted—reduces this heat to extend blade life and improve the quality of cuts.
Liquid bandsaw coolant lubricates the blade and flushes away excess heat and metal chips during the cutting operation. It can also speed up the cutting process and reduce friction and tool wear. For maximum safety, a bandsaw coolant should be free of contaminants that can cause skin or respiratory irritation, as well as contain corrosion inhibitors to keep the machine in good condition.
A highly efficient cooling system incorporates a flood system through the guide blocks to force the coolant directly into contact with the blade and material. Correct application through the guides effectively reduces frictional heat and provides maximum lubrication for the chips. Small machines may require only a misting spray while larger devices need an ample supply of coolant to control the heat produced during the cutting operation.
Coolants are available in many forms, including full and semi-synthetic products. The choice depends on the workpiece materials being cut and the speed at which the metal is sawed. Hard or work-hardened metals need a higher metal band saw degree of extreme pressure (EP) lubricity and a greater amount of evaporative cooling to prevent the blade from becoming too hot. Synthetic coolants do not stratify in the sump tank and typically require a lower mix ratio than oil-based solutions.
Blade
The cutting blade on a metal band saw is the heart of the machine. When it is well conditioned, the machine will produce excellent quality cuts. Generally, the blade must be selected according to the material and thickness of each cut. Tooth shape and tooth pitch also play a part in the quality of the cut.
For a solid metal cut, a tooth count of 6-12 teeth per inch is suitable for most materials. For structural materials, consider the wall thickness when choosing the appropriate tooth size. Too aggressive a tooth count may cause the teeth to catch on the side walls of the material, resulting in premature blade wear and motor failure.
Special care is required to break in nickel-based alloys such as Inconel, Hastelloy and D2 tool steel. These alloys tend to harden quickly and require greater feed pressure during the break-in process.
Guide arms should be adjusted so the saw band is exposed to as little upward stress as possible. This will reduce stress cracks in the band and improve blade strength. It is important to periodically inspect and adjust the guide arms, as they must be positioned correctly in order to provide maximum support for the band. Frequently checking the condition and adjustment of the chip brush will help prevent work hardened chips from being carried into the blade gullets, which can damage the band set or create a scoring effect on the cut surface.
Guides
A metal band saw’s guides are designed to twist the blade in the correct alignment for cutting and support it from the back and sides. This ensures that the blade is cutting through the material and not contacting the workpiece directly, which can cause damage to both the blade and the machine. Using a Carter Guide Kit can improve performance and increase accuracy of the blade.
The guide posts are typically adjustable, allowing users to set the proper blade-to-workpiece clearance and minimize blade deflection during cutting. If a band saw’s guide post adjustment is too tight, you can hear and see the join in the blade jump as it passes through the bearing guide adjustments. You can fix this by slackening the blade tension very slightly and turning the locking bolt or tracking adjustment set screw on the upper arm until the blade moves freely and smoothly through the guides.
If your machine is experiencing teeth stripping as a result of feed pressure being too high, you can solve this problem by reducing the pressure on the blade or by switching to a different blade. Changing to a lower tooth pitch will also help, as will ensuring that the blade is being fed at the right speed for the type of material you’re cutting.
Lastly, making sure the saw’s table is square to the blade can prevent the cut from becoming crooked. You can check if the saw’s table is square to the saw by looking at the trunnion assembly that secures it to the bandsaw cabinet or casting. If the trunnion is not square to the saw, this can lead to wavy cuts and may even damage the trunnion.
Safety
When using metal band saws, it’s important to follow proper safety measures to prevent injuries and damage to workpieces. This includes using industry-established personal protective equipment (PPE), such as safety glasses or goggles that meet ANSI meat wrapping machine standards, and ear protection that protects against high noise levels during operation.
In addition, a clean and clutter-free workspace is necessary to reduce the risk of trips and falls near the machine. Inspect the machine and blades regularly for wear and tear and replace worn-out parts to ensure safe operation. Performing maintenance and blade adjustments with the power off is essential to avoid accidental start-ups that could result in injury.
Finally, it’s important to carefully support the material being cut on the bandsaw table. Loose materials can snag on the blade, leading to serious injuries, and should be secured using clamps or vises.
Using push sticks and other accessories can increase accuracy while keeping hands at a safe distance from the blade. It’s also critical to use a miter gauge or jig when cutting angles to ensure the correct positioning of the workpiece. Finally, it’s crucial to understand the limitations of a metal cutting band saw before attempting to cut anything other than specified material. For example, cutting hardened steel files or other tool steel can cause damage to the machine and create dangerous sharp edges.
