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Get the most out of your band saw

In the case of band saws, as with other tools, there are procedures to follow that extend the life of both the machine and the tool itself. The correct pitch in relation to the material being cut, the right speed and feed rate, proper belt tension, lapping of the saw, cooling during the cutting process, and attention to the machine’s condition are all necessary to take full advantage of the cutting belt’s capabilities.
Excessive heat and vibration are the biggest enemies of the saw. It is relatively easy to see the vibration of the belt and determine the high temperature created by the friction of the saw against the material being cut. A more difficult issue is to localize the causes of this phenomenon. Proper diagnosis through observation is the key to optimizing saw life and cutting efficiency. With a properly functioning saw cutter, the saw will cut evenly, straight and quickly, resulting in a lower unit cost of cutting.

Correct pitch in relation to the material to be cut
Choosing the right saw for the job is a basic criterion for effective cutting. The first step is to learn the uses of the saw. The combination of machine parameters, the type and properties of the material, its dimensions, and information about whether it will be cut in bundles or individually implies the choice of the saw to be used. The selection of the correct belt speed and feed rate depends on this.
Once the key factors are identified, the appropriate TPI pitch (number of teeth per 1-inch length) should be selected. As a general rule of thumb for obtaining a correct cut is to choose a pitch so that at least three teeth are in contact with the material being cut, but no more than 24. The most effective cut is obtained with a TPI in the range of 6-12.

When the new cutting belt is properly attached and prepared for cutting, it should be reached. Cutting at full speed with a new saw can lead to damage to the teeth of the band. The undotted tape has very sharp teeth, prone to microscopic damage. Lapping the belt allows it to meet the harsh cutting conditions.
Saw manufacturers suggest setting the machine at about 50% (for easily cut materials) or 25% (for hard-to-cut materials) of the feed rate while maintaining a constant cutting speed during lapping, for at least 15 minutes of belt operation. This will allow you to gently round the edges of the tape. Lapping the saw significantly affects its service life. Even a short lapping is better than skipping this procedure. Saws with coated teeth are smoothed, hence do not require traditional lapping, making them the exception to the rule.

Lapping principle of the band saw
Speed and feed value
After the correct selection of the cutting belt and its proper mounting in the belt cutter, it is necessary to set the belt speed and feed value. Saw speed refers to the rate at which the saw blade cuts through the surfaces of the material being cut. The cutting speed is limited by the machinability of the material and the amount of heat generated by the friction of the strip against the object being cut. Setting the belt speed too high when cutting through hard-to-cut materials generates excessive heat, resulting in uneven cutting and chipping of the saw, resulting in premature wear.
Most belt cutters have a feed control mechanism. Feed rate determines the relationship of the rate at which the saw cuts through the material being cut to the penetration depth of the blade. The feed rate is measured in IPM (inches per minute). The optimal feed rate is determined by the TPI of the saw, the cutting speed and the size of the saw notch. From a productivity standpoint, it is most beneficial to use the highest possible feed rate. It should be noted that such action significantly reduces the life of the tape. In practice, achieving the lowest unit cost of cutting means a compromise between productivity and the life of the band saw. The correct speed and feed rate of a band saw can be determined by carefully observing the chips produced in the cutting process.

Part two of the article.

Observation of chips
Observation of the chips produced during the cutting process is an excellent method for diagnosing the correctness of the cutting speed and feed rate. Pay attention to their shape and color. The chips should be warm to the touch, twisted and shaped like the numbers 6 or 9, while the color should be similar to the color of the material being cut. If the shavings have turned from silver to brown or blue, it means that too much heat has been generated during cutting. In this case, reduce the cutting speed and/or feed rate. Continuing to cut with poorly selected speed and feed parameters will result in premature wear of the saw. Notch capacity is another factor that affects chip formation, and thus effective cutting.
Proper drainage of chips from the notch allows them to form properly. If the saw cuts too much material, the chips will be blocked in the rebate, causing more friction and the release of excessive heat. The larger notch capacity allows for increased cutting capacity.

Observation of chips
Application of coolant
The basic principle when we talk about effective use of cutting belt capabilities is to use clean, properly mixed coolant. It reduces friction and helps dissipate chips.
Proper maintenance of the cutter
Maintenance of the belt cutter is another key factor for getting the most out of the cutting belt. Here is a short list of tips that, if followed, will ensure effective cutting.
Guide wheels – remove all chips, make sure that the wheels turn freely.
Saw tension – use a strain gauge to measure saw tension.
Belt guiding system – pay attention to whether the saw is properly fixed in the guides and whether the belt guiding system is clean.
Cleaning brush – make sure it does not allow chips to re-enter the cutting area.
Guides – check for chipped or cracked guides, make sure they properly press the saw against the material, make sure they are positioned as close to the cutting area as possible.
Coolant and lubricant – use clean coolant properly mixed with water supplied to the saw work area, check concentration ratios with a refractometer; remember to mix the coolant with water according to the manufacturer’s recommendations.

There are many factors that contribute to the band saw wearing out too quickly. To make the most of the belt’s capabilities, it is necessary to use saws with correctly selected pitch (TPI), define the right cutting parameters for the material being cut (speed and feed value), remember to run-in new saws, take care of properly operating the band saw machine, and use high-quality coolant. The challenge is worth taking. When all the variables are taken into account, it becomes clear that cost-effective and efficient cutting is not all that difficult to achieve.

Based on: Practical Welding Today