A sanding belt is grains of abrasive glued to a cloth or paper backing, and both the backing and the glue react to the air around them. A belt kept in a damp shed or above a radiator can curl, lose grain or split at the joint the first time you run it. Storing belts well costs nothing and saves belts.
What abrasive makers recommend.
Abrasive makers give similar, but not identical, figures. Klingspor’s German site gives the ideal as about 18 to 22 °C and 45–65 % relative humidity; its US site gives 60 to 80 °F (about 16 to 27 °C) and 35–50 %, with 70 °F and 45 % as ideal. Both point the same way: a steady room temperature and moderate humidity, with about 45 % inside both ranges. Both also say to keep belts away from heat, damp and direct sunlight, and in their original packaging until you use them.
Why damp and dry air matter.
The backing takes up moisture from the air and gives it off again. In damp air it absorbs water and swells; in very dry air it loses water and shrinks. Either way the belt changes shape a little, which makes it curl, track badly or strain the joint. Cold matters too: a belt brought from a cold garage straight onto a warm machine is more likely to crack.
In a home workshop.
- Keep them indoors if you can. A cupboard in the house is usually closer to those conditions than an unheated garage or shed. If the workshop is cold or damp, keep belts in a closed box and bring them into the workshop a day before use so they can adjust.
- Off the floor and away from walls. Klingspor advises against storing abrasives on concrete floors or anywhere damp; outside walls are cold and damp too.
- Away from heat. Not on a windowsill, above a heater or next to the stove.
- Hang, don’t fold. Hang belts over a wide peg, dowel or length of pipe so they keep their round shape; Klingspor’s US site recommends non-metal cores at least 4 in (about 10 cm) across. Never crease a belt or put weight on it; a kink in the backing becomes a bump that hammers the work.
- Keep the box. The original packaging protects the belts and carries the size and grit. If you take belts out, write the size and grit on the hook or shelf.
- Use the oldest first. Put new belts at the back so older ones are used before they age.
Before you fit a stored belt.
Check it before it goes on the machine: look for cracks at the joint, frayed edges, missing grain or a curl that won’t relax. A damaged belt can break at speed, so throw it away. Klingspor recommends taking belts out of their packaging about a day before use so they adjust to the workshop, and hanging wide belts two days before use with the lower loop weighted.
Keeping a spares list ↗︎Sources
- Klingspor (Germany), “Storage of abrasives”.
- Klingspor (USA), “How to Store and Handle Abrasives”.