Cutting tips that lead to better welds
May 15, 2013
For performing structural cuts with a band saw, a few simple tips will help in your quest to make straight cuts, which can ultimately lead to better welds.
When band saw cutting I-beam, square, and round tubing, straight cuts are crucial to preparing the part properly for welding. Parts with crooked cuts make welding difficult, to say the least, and as a result, welders often must use a filler or additional welding wire to fill the gap left by the uneven edge. In more severe cases, the parts with uneven cuts may have to be recut or scrapped altogether, which is both costly and time-consuming.
If you are performing structural cuts with a band saw, consider these tips to help ensure that edges are straight and that welders can join parts easily and efficiently. Keep in mind the importance of routine maintenance on the band saw machine. If a machine has problems with its feed system or its variable-speed system, it will negatively affect the life of the band saw blade.
The best way to ensure the cuts you make will be straight is to set your sawing parameters correctly. Set the machine to the correct blade speed and cut rate for the material being cut. As a rule, slow the blade for tough material and increase speed for softer material.
Also, check to make sure the conveyor rollers that hold the material are aligned properly. Rollers that are out of alignment can lead to crooked cuts.
Use a gauge to measure and set the tension on the blade in the band saw machine. Most band saws work best with the blade tension set to a minimum of 25,000 PSI or a maximum of 32,000 PSI. Anything less than 25,000 PSI leads to poor beam strength, band fatigue, or crooked cuts. Tensions set to 32,000 PSI or more can break the band, crack the gullets, or wear out the machine bearings.
For applications that involve cutting through a weld seam on tubing, it is easier and more efficient for the band saw blade to enter the material from the back of the weld seam. Cutting directly into the weld seam serves as a shock point to the blade teeth and often results in shorter blade life or teeth strippage.
When band sawing bundles of material, it is best to strap down the entire bundle or tack weld the ends of the bundle to prevent any pieces from moving. If the individual pieces vibrate or move during the cutting process, there is a possibility that the teeth will strip.
The proper amount of cutting lubricant, also known as coolant, will help extend blade life. Band saws use a flood-coolant or a mist system to lubricate the blade. Not only does lubrication help maximize blade life, it also helps minimize the buildup of metal chips that result when the material is cut. Coolant should wash over the blade as it enters and exits the cut. Although the coolant is recirculated and used continuously throughout the cutting process, be sure to replace water that evaporates from the mixed solution.
Be sure to break in new band saw blades before you ramp them up to full-speed cutting. This practice will hone the teeth and extend blade life. The best way to break in new bimetal blades is by reducing the normal feed rate by half during this initial period. The band speed isn’t what breaks teeth during blade break-in; it’s the pressure an excessive feed rate produces that is most damaging.
To break in your bimetal saw blade, multiply the recommended blade speed by 25 percent, and cut that number of square inches. Be sure to run the blade at 50 percent of the recommended blade feed rate. Once you approach the end of the break-in period, gradually bring your band saw feed rate up to normal.
The right band saw blade makes all the difference when cutting structurals, where the desired outcome is a clean, straight cut that simplifies weld prep applications. Be sure to choose a blade that can withstand the stresses of structural cutting, produce a smooth finish, and ensure maximum blade life. Also, optimal tooth geometry is key to creating faster cutting rates, which increase productivity.