Adjusting band saws and changing the saw blade
The band saw is one of the most popular stationary machines in the woodworking shop. It is versatile and expands the production possibilities enormously. Compared to other machines, a band saw requires more maintenance in at least one respect. If the band saw has not been used for a long time and at the latest after changing the saw blade, its blade guide must be readjusted. We explain how to change the saw blade on a band saw and give you tips on how to adjust the band saw correctly afterwards.
Three-roller saw band guide
The saw blade is usually supported by two guides, one fixed under the work table and one on the upper saw blade cover, which is adjustable in height. The band guide supports the saw band whenever it is in danger of running off track. Otherwise, a correctly adjusted saw blade guide allows the saw blade to run freely without permanent contact. There are different types of saw blade guides for band saws. A simple form is the guide with lateral sliding pins and a ball bearing behind the saw blade. This sliding pin guide is usually found on smaller band saws. The most commonly used band guide is the so-called three-roller saw band guide, in which the saw band is also guided laterally by ball bearings. With a roller guide, the rolling resistance of the ball bearings is significantly lower than the frictional resistance of guide pins. As a result, the saw blade heats up less and expands less. The guide rollers can therefore be positioned closer to the saw blade. In this article, we explain how to adjust the three-roller band guide. However, adjusting a sliding pin guide works in a similar way and there are numerous special forms. For example, there is a precision band guide for the DICTUM BS 270-10 and BS 320-12 band saws, which enables precise saw cuts with very narrow saw bands. In our video instructions we show, among other things, how this is fitted and adjusted.
How is the saw blade changed on a band saw?
First disconnect the machine from the power supply, remove all stops and open the doors. Remove all safety covers that could block the saw blade and the table insert in the work table. The band guide is loosened and pushed back slightly, if possible. The saw blade is then slackened by loosening the handwheel for the blade tension. On some models, for example the DICTUM BS 360-14, the saw can be released using a lever.
You can now carefully remove the saw blade from the rollers and unthread it from the saw blade guide and cover. Make sure that the saw blade is not bent or kinked too much in the process. The new saw blade is then threaded in the opposite direction and placed loosely on the upper and lower rollers. Sometimes the belt tension on the handwheel needs to be loosened slightly for this.
Place the new saw blade approximately in the centre of the rollers. The saw teeth do not need to protrude over the front of the rubber bands, as is sometimes assumed. The saw blade is now slightly pre-tensioned again by turning the handwheel. The band tension depends on the width of the saw band. Wider saw bands can be tensioned more than narrow ones.
What should I do if the band saw blade jumps off the rollers?
The inclination of the roller is usually adjusted using a handwheel on the back of the band saw. Loosen the lock nut on the handwheel so that you can adjust the inclination. To adjust the running of the band saw blade, turn the upper roller slowly with one hand. The saw blade should run as centred as possible on the roller. If the saw blade tends to run backwards, the roller must be tilted slightly forwards (B). If the band runs forwards and threatens to jump off the roller, the upper roller must be tilted backwards (A). If the saw blade runs in the centre of the roller even after several revolutions, you can fix the setting on the handwheel with the lock nut.
The saw blade is aligned by tilting the upper roller.
How is the band guide adjusted on a band saw?
To achieve optimum cutting results later on, adjust the saw blade cover and therefore also the upper blade guide to approximately the height at which you will be working. First, adjust the rear guide roller on the upper guide so that it is positioned just behind the saw blade. The saw blade should not touch the guide rollers when not under load (when not sawing). The rear roller should support the saw blade and prevent the saw blade from being pushed backwards due to excessive feed of the workpiece.
Schematic diagram of the upper three-roller guide.
You can now align the two lateral guide rollers one after the other as close as possible to the saw blade. The rollers should be approx. 2 mm behind the base of the tooth and should also not rotate permanently. They should only support the saw blade when it is under lateral load. To check this, turn the upper roller again by hand. If the settings are correct, the guide rollers will not rotate permanently. However, it is normal for them to rotate slightly from time to time, for example at the point where the saw blade has been soldered together or when swarf sticks to the blade. Once the upper roller guide has been adjusted, you can adjust the lower guide rollers in the same way. Here too, the rear guide roller is first brought close to the back of the saw blade and then the side guide rollers are aligned with a minimum distance to the saw blade. As before, the rollers only rotate from time to time.
Before the first test run, all safety covers are refitted and the table inserts are inserted. For the test run, the band saw is only switched on briefly and then switched off again immediately. If the saw band jumps off the rollers, the machine has already stopped. If everything is OK and the replaced band saw blade runs smoothly, you can make a test cut. If this is also successful, you can continue working on your band saw.
Common errors and possible causes and solutions
What to do if the saw cut is not at a right angle?
The worktable may be slightly tilted. Use a square to check whether the worktable is at right angles to the saw blade and correct the setting. If the saw blade tension is too low, this can also cause the saw cut to run. In this case, increase the blade tension on the upper handwheel.
What should I do if the saw blade jumps off the rollers despite correct settings?
If you have set the inclination of the upper roller correctly, this should not happen. Check whether the rubber bandages on the rollers are dirty or badly worn. Clean dirty bandages or replace worn or damaged rubber bandages. It often happens that the saw blade is pulled forwards out of the guide when the workpiece is retracted. If this cannot be avoided, always retract the workpiece slowly and ensure that the saw blade remains in the guide.
What should I do if the band saw makes unusual noises?
Regular noises, such as chattering or banging, can have several causes. On the one hand, it may be due to an imbalance. Sometimes chips and dust fall onto a roller (usually the lower one) when changing the band saw blade and remain between the spokes or on the inner edge. Check and clean the rollers. Slamming noises at slightly longer intervals are usually caused by a damaged or kinked saw blade. Check the entire length of the saw band and replace it if necessary.
What should I do if the band saw no longer starts after changing the saw blade?
Check whether the mains plug is plugged in. If this is the case, it is usually due to the safety contact switches, which stop the bandsaw as soon as one of the doors is opened. Check that all doors are firmly closed and that the safety contact switches are functioning correctly.
