Chip Formation and Color

There are various factors that can affect bandsaw efficiency, and using the correct sawing parameters — band speed and feed rates — is one to consider. Knowing about chip formation and color is important to determine the correct use of feed rate.

A bandsaw blade’s teeth are razor-sharp, and the result of any cutting process includes the chips produced. They are discarded yet hold a vital clue to the success of any cutting procedure. The bandsaw operator can and should inspect the chips in order to achieve maximum cutting efficiency.

Chips are the layers (shavings) of metal removed from the material being cut as a result of the action of the cutting tool. The ideal chip formation is thin, curled, and warm to the touch, not hot. The ideal shape would be to have them resemble the numbers 6 (9).

Chip color should be similar to the material being cut. Chips that change color — silver to brown for example — mean that too much heat is being generated. Bandsaw speed, the rate of feed, or both need to be reduced. Blue chips indicate extreme heat and will result in early failure of the blade.

Chips that form neatly show a properly chosen blade. The ideal chip is warm to touch. If the saw blade is cutting correctly, the chips should have a bright metallic color to them.

Feed rate is the linear travel of the work piece into the bandsaw, which is often accomplished in Inches Per Minute. Higher feed rates result in increased productivity, but it will also help to reduce the life of the blade.

High feed and speed rate produces blade heat which causes premature blade failure. Chips formed while the blade is over feeding have a heavy, thick tan or blue color — except for Stainless steel.  The operator needs to reduce feed pressure, slow the speed, or do both to prevent damage to the saw blade.

If a proper break-in process was performed, the chips will indicate this as well. A proper break in procedure is performed in order for a productive and low-cost sawing procedure to occur. With proper break-in procedure, the chips should be springy and curled with no color — the way they will if proper feed rate is applied.

Insufficient feed rate will result in small flakes and excessive feed rate will produce heavy, blue chips.

Gullet Capacity is another factor that impacts cutting efficiency and the chips produced.

The gullet is the curved area between two bandsaw teeth into which the chip curls. Cutting stops when gullets are full.

Hard materials produce small chips and need a small, strong tooth shape blade. Soft materials produce large chips that quickly fill up the gullets. Soft materials need a large gullet saw blade in order to be able to accommodate the chips during cutting.

A blade with proper clearance for the cut allows the chip to curl up uniformly and fall away from the  gullet. Without proper clearance, the chips can jamb into the gullets of the blade and cause increased resistance. This leads to wasted energy and bandsaw machine damage.

Efficient sawing includes examining of saw chips during the operation. Bandsaw operators should use the chips to their advantage with regard to the status of the bandsaw process. If blade life, optimization, quality productivity, and efficiency of the blade are important, then it is worth it to examine the chips being produced and understand what their feel and color changes mean.

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