Measuring Belt Tension

Most belt sanders need certain conditions to work properly. For example, if you are using 80-durometer steel or rubber contact roller heads, apply a pressure of 20 to 25 pounds per linear inch of belt width. For platen and combination heads, apply 15 to 20 pounds of pressure.

There is a wide variety of tools available for measuring belt tension, including specially designed tools. You can use an OEM-recommended belt tension gauge, but standard air regulators can also be converted into measuring tools.

The regulator should have two outlet ports and one inlet port. Attach an air cap to the inlet port that corresponds to the air line coupler closest to the belt sander. Next, fit a good pressure gauge to one of the outlet ports. The other must match the thread of the belt tension gauge.

Once the tool is complete, thread the gauge into the outlet and connect the air supply line to the regulator. To determine the accuracy of the readings, compare the correct gauge with the suspect gauge at different PSI levels.

Beware Of Air Leaks

Problems with the tensioning of abrasive belts can be caused by air leaks, which are common in installations using compressed air. There may be leaks in the air supply system and in the joints of the tensioning cylinders. Make sure that all leaks are repaired and that periodic air checks are carried out throughout your installation. A more efficient compressed air system can save you money.

Sanding Belt Tension Formulas

Use the following formula to calculate the correct tension for your sanding belt.

Generally speaking, wood sanding applications such as mold sanding (using narrow cloth belts) require belt tensions of approximately 40 psi. There are, however, some exceptions. In planning operations, for example, belt tension is typically between 70 and 90 psi.

For intermediate wide belt sanding, a tension of 60 to 75 psi is usually used. (Intermediate usually refers to 60 to 220-grit abrasives.) Paper belts should be tensioned at about 20 to 25% less than cloth belts in these applications. This is because cloth belts stretch slightly during use, while paper belts do not. To determine specific air tension settings, consult the manufacturer of the wide belt machine.

In drawer sanders, which sand the inside lip of a drawer front, it is best to use the least amount of belt tension. If you turn off the machine, you should be able to rotate the belt by hand easily. If the belt has stretched after 10 minutes of use, increase the tension of the sander.