How Much Tension Should A Belt Sander Have

Benchmark Abrasives is constantly teaching its customers how to select the best abrasive for their needs. Ensuring your belt sander is adjusted correctly is just as crucial to achieving the most outstanding results as choosing the suitable abrasive.

In order to function, all abrasive belts, which are extensively used in grinding and sanding equipment, need tension. To prevent the belt from slipping on the driving wheel or tracking off the machine, they should be just barely tensioned.

On specific sanding machines, the belt tension is fixed. For instance, the loaded spring on portable sanders is fixed at the factory and cannot be changed. Nonetheless, the majority of sanding machines come with some kind of tensioning mechanism. Examples include screw-type mechanisms, pneumatic cylinders, and weighing mechanisms. This blog discusses the ideal tension for a belt sander and how to get it.

BELT TENSION: LOW VS. HIGH

Finding the ideal setting in cases where the belt tension is not fixed may need some trial and error. An overview of the indicators that your setting can be too high or too low is provided below.

LOW BELT TENSION

Low belt tension can cause a number of symptoms, such as issues with belt tracking. For instance, tracking off in the same direction each time could be a sign of severe tracking wheel or roll wear or a length change from side to side. Additional indicators consist of:

• The belt breaks as it folds over. This issue can also be brought on by low belt tension combined with roll wear. 
• The printing on the belt's back shows signs of wear. The print on the rear is worn off when it slides on the drive roll.
• The sections in progress have skip marks. When the belt slips on the drive roll, it can stop or lose speed, which is what could have led to the marks. Under conditions of heavy load, this may be a common issue. 
• There's a brief, high-pitched whine when the head turns on or parts are processed. The belt might have come loose from the driving roll in this instance as well. Even very little stress causes the belt to moan. 

Low tension might shorten the belt's operational life over time. This is due to the fact that when the belt slips, less pressure is applied, which prevents the abrasive from properly breaking down and sharpening.

HIGH BELT TENSION

Because tracking cylinders are usually smaller than tension cylinders, excessive belt tension may cause them to overheat. Premature failure of the head's idler rollers, tracking, and drive bearings is another possibility. The more belt strain on any kind of grinding or sanding equipment, the more wear the associated bearings receive.

Additional indicators of excessive belt tension include:

• The sanding belt breaks easily. When a belt is overtightened, it is less able to handle large or varying shock loads. 
• Wear occurs on all rollers within the head. The belt often wears around the outside edges of the rolls, where it tracks back and forth. As belt tension increases, such wear increases disproportionately.

For screw-adjusted tension devices, it can be challenging to establish the optimum tensioning amount unless you have substantial familiarity with that equipment. After the machine is switched off, the belt should rotate five or more times. The tension may be too high if the belt stops very quickly.

MEASURING BELT TENSION

Most belt sanders need certain conditions in place in order to function correctly. For example, if you are utilizing steel or rubber contact roll heads with an 80 durometer, apply 20 to 25 pounds of pressure per linear inch of belt width. In the case of platen heads and combination heads, use 15 to 20 pounds.

A variety of equipment is available for measuring belt tension, including special tools developed for the purpose. You can utilize an OEM-recommended belt tension gauge, but standard air regulators can easily be transformed into measurement tools. 

The regulator must have two output ports and a single inlet port. Attach an air plug to the inlet port that corresponds to the coupler on the airline nearest the belt sander. Next, add a suitable air gauge to one of the outlet ports. The other should be threaded to match the belt tension air gauge.

After finishing the tool, thread the gauge into the outlet port and connect the air supply line to the regulator. To determine the accuracy of the readings, compare the proper gauge to the suspect one at different PSI levels.

WATCH OUT FOR AIR LEAKS

Air leaks, which occur frequently in compressed air facilities, can cause abrasive belt tension difficulties. There may be leaks in the air supply system as well as tension cylinder seals. Ensure that all leaks are rectified and that regular air audits are performed across your building. An efficient compressed air system might help you save money.

ABRASIVE BELT TENSION FORMULAS

To calculate the proper tension for your abrasive belt, use the following formula.

Tension Cylinder Area = π × Radius2
Abrasive Belt Tension = (Tension Cylinder Area × Gauge Pressure in PSI) / Belt Width

Wood sanding applications, such as mold sanding (with narrow cloth belts), often demand belt pressures of around 40 psi. There are a few exceptions. Belt tension in planning operations, for example, is usually 70 to 90 psi.

For intermediate wide belt sanding, a tension of 60 to 75 psi is typically employed. (Intermediate abrasives usually range from 60 to 220 grit.) Paper belts should be tensioned roughly 20 to 25% less than cloth belts in certain situations. This is because textile belts expand significantly when in use, whereas paper belts don't. Consult the broad belt machine's manufacturer for particular air tension settings.

The least amount of belt tension is recommended when using drawer sanders to sand the inside lip of a drawer front. Turning off the machine should allow you to rotate the belt by hand easily. If the belt has stretched after 10 minutes of use, raise the sander's tension.

CONCLUSION

Correct belt tensioning can maximize product life, produce the most incredible finish, and extend the life of your belt sander. If you're unsure about the necessary specifications, consult an abrasive manufacturer. Our abrasive professionals at Benchmark Abrasives take pride in providing customer and technical support.