August 11, 2011

Choosing the Correct Backing for Your Sandpaper & Abrasive Products

Whether paper, cloth or film, the backing used for coated abrasive products must be smooth enough for a uniform adhesive coating, strong enough to withstand grinding pressures and flexible enough to conform to contours if that is necessary to your application.
Paper: The paper backings used for coated abrasives are highly specialized technical papers made to very exact specifications for abrasive use, thereby assuring certain essential physical properties such as finish, strength, adhesion, flexibility and weight.

Paper weights are determined by the number of pounds in a papermaker's ream of 480 sheets that are 24" x 36" in size. The standard paper weights used in coated abrasives are shown below and are indicated by a letter code which appears immediately after the grit size on the finished product backing. Briefly stated, the lighter the backing, the greater the degree of flexibility and the heavier the backing, the greater resistance to tearing.
  • A-weight (40 lbs) -Light and flexible. A weight is primarily used for sheet products used on hand sanding operations in grits 80 and finer.
  • C-weight (70 lbs) -Stronger and less flexible than A weight. This backing is chosen for hand sanding and for use on small, portable power sanders. Used for intermediate sanding in grits 36 through 80.
  • D-weight (90 lbs) -Stronger and less flexible than C weight. This backing is also used for hand sanding and small, portable power sanders on coarse and intermediate grits 24-80.
  • E-weight (130 lbs) -Stronger and less flexible than D-weight, this backing is primarily used on roll, belt and disc applications where high resistance to tearing is needed.
  • F-weight (165 lbs) -The strongest, least flexible paper backing utilized. Used primarily for heavy-duty sanding discs, sheet goods and sanding belts used in the floor sanding market and paper wide belts used in woodworking applications.
Cloth: Cloth backings are more durable than paper, offer greater resistance to tearing, and tolerate continual bending and flexing during use. The cloth used for abrasive backings are manufactured in the traditional way most cloth is processed--by interlacing threads running at 90' angles with each other. The friction at the numerous points of intersection hold the fabric together. Cloth used for abrasive backings often requires desizing, shrinking, drying, stretching, filling and calendering in order to produce the desired strength, flexibility and coating surface.

The standard cloth weights used in coated abrasives are also indicated by a letter code which appears immediately after the grit size on the finished product backing.

  • J-weight (Jeans) -The lightest and most flexible cloth backing, this backing is used where finish and uniformity of surface are more important than stock removal. Most often seen on abrasive shop/utility rolls, cloth sheets and sanding belts. Ideal for finishing, blending and where considerable flexibility and conformity are required, such as contour work on curved surfaces.
  • X-weight (Drills) -Stronger and stiffer than J-weight, this backing is used on a multitude of abrasive products from coarse grit stock removal through fine grit finishing and polishing. Consistent productivity, good finishes and long product life are characteristics of abrasive products made on an x-weight backing such as sanding belts and cloth sanding discs.
  • Y-weight (Heavy Duty) -The strongest cloth backing utilized, this backing is used on coarse grit products designed for extreme pressure and heavy stock removal operations. Used most often in heavy duty, long life premium abrasive belt materials.
Polyester Film: Polyester based film backings offer special properties that lend themselves to specialized sanding applications. Film backed abrasives offer thicknesses having ultra tight tolerances...which is important for the electronics, fiber optics and surgical instrument/medical applications. The benefits of a film backed abrasive product is now also being realized in the automotive and solid surface markets.

Basic Sanders

The basic styles of portable sanders haven’t changed very much over the years. We have some old advertising posters from the Rockwell Manuf...