Breaking in a bandsaw blade contributes to life, cut quality

A new blade has a razor-sharp tooth with a delicate tip (left). When lapped properly, it has a small radius (center). If used without a break-in period, the cutting edge may chip and become jagged (right).

In today’s competitive environment, everyone is looking for ways to make their business operations more profitable. Sometimes cutting costs can seem like an attractive way to do it. However, simply reducing the cost of a piece of equipment or a process is no guarantee of success. A better goal is to become more efficient at work so that manufacturing operations are more productive, thereby improving the bottom line.

In bandsaw cutting operations, an important way to increase productivity is to extend blade life. Fabricating and metalworking shops are always looking for a bandsaw blade that will last longer and deliver better quality cuts. And while cost per blade is important and very easy to measure, it’s cost per to cut it really matters. Using a bandsaw blade that lasts longer minimizes cost per cut and is directly correlated to productivity.

The life of a bandsaw blade and the quality of the surface finish at the cut end are not solely determined by the blade manufacturer’s product design. Machine maintenance and operating practices can contribute to, or hinder, this performance. Assuming the bandsaw is well maintained and the operator adheres to the manufacturer’s recommended speed and feed settings, there remains one critical, often overlooked step: break-in the blade.

Virtually all manufacturers agree that a blade that has been lapped properly has a noticeably longer life than one that has not. So why would the operator skip this important step? Some say it’s not worth it because it translates into the short-term cost of reducing feed pressure for the first 25 to 100 square inches of cut. These operators overlook the long-term benefit, which is extended life with less frequent blade changes and, therefore, increased uptime. A proper break-in period also improves the surface finish of cuts.

Breaking down the break-in process

What does lapping a blade actually do? Newer bandsaw blades have very sharp edges on the teeth that can break easily if the blade is not properly conditioned. This is similar to a freshly sharpened pencil: the sharp tip can break, leaving an irregular, jagged tip that doesn’t write well. Starting with a little pressure, then gradually increasing the pressure, sharpens the tip of the pencil or the leading edge of the tooth of the blade to a very fine radius. On the saw blade, this radius allows the chip to shear off the workpiece more easily and also gives the required support to the tip of the tooth, which experiences extreme forces during the cutting process.

Once the teeth are sharp and properly lapped, the blade will cut faster, straighter and longer than a blade that has been broken improperly or not at all.

Break the blade, rake productivity

The process for lapping a bandsaw blade varies from application to application and depends on the characteristics of the material being cut. The main consideration is that the break-in speed is the same as the normal operating speed, which most manufacturers specify in surface feet per minute (SFPM).

For softer materials, such as carbon steel and aluminum, common practice is to reduce feed pressure to 50% of normal cutting feed pressure for the first 50 to 100 square inches. The transition to maximum cutting speed should be gradual.

For harder materials such as nickel-based alloys, as well as other difficult-to-cut materials including hardened steels, tool steels, and stainless steels, the honing practice is generally not as rigorous. A supply pressure of 75% of normal pressure on the first 25 to 75 square inches is sufficient. The increase in supply pressure must be done gradually, reaching 100% after 50 in².

The saw operator must be careful when increasing the feed pressure, as doing it too quickly can lead to vibrations that disrupt the cutting process.

Elizabeth J. Harless