Tech Talk
What is “Backing Material” for Coated Abrasives?
Having selected an abrasive type and size, the next choice is backing. Coated abrasive backings are made from paper or cloth. Paper backings are the least costly and come in a variety of weights. The weight is measured by the weight of a ream (480) of 24- by 36- in sheets and given a letter code: A, B, C, D or E. “A” weight is 18 kg (40 lb), “B” weight is 23 kg (50 lb), “C” weight is 30 kg (60 to 70 lb), “D” weight is 45 kg (90 to 100 lb), and “E” weight is 60 kg (130 lb). Paper belts are nearly always “E” weight; lighter papers are termed cabinet paper. Paper backings are used when pliability and strength of the backing are not important. Paper-coated abrasives are most commonly used in the woodworking industry.
Cloth backings fall into a number of categories. There are two twill weave cloths: “drills,” marked with an “X”, and “jeans,” marked with a “J”. The main differences are that drills are made from heavier threads with fewer threads per square inch than jeans. Drills are the stronger of the two and used primarily with coarse abrasives for heavy work. Jeans are more flexible and ideally suited to finishing type operations.
The key factor in the selection of a cloth belt is its tearing limit under pressure cloth belts are pushed to their limit with today’s demands of cutting speeds and stock removal rates. Synthetic belts are now being manufactured with complex weave patterns, which provide directional strength and longevity.
