The handling of coated abrasives in the woodworking industry is sometimes neglectful. Abrasives are often regarded as being impervious to rain, heat, cold, and rough handling, but this is not the case. In many plants, there is no special room set aside for proper storage of abrasives. An ideal storage room is one in which all the walls are inside partitions, rather than against any outside walls of the building. Abrasives should be kept away from windows and any direct heat source. Air-conditioned rooms are recommended for all users with large abrasives inventory.

Coated abrasives should not be stored on concrete floors or near any area of dampness. If abrasives are to be stored
for any length of time, it is strongly advised to store them in the original packing containers or packages. Belts which are already out of the package should be rolled up and stored on end on a shelf.

Humidity Can Cause Many Problems
Relative humidity is an important factor in the transport and storage of coated abrasives. Optimum conditions are 35% to 50% relative humidity (45% is ideal) at a temperature range of 60° to 80°F (70° F is ideal) or 18° to 26° C.

Problems arise as soon as the relative humidity changes. An example of such a change is the beginning of the heating season when the humidity in heated rooms drops by 10% to 15%. The other extreme is after a lengthy period of rain or foggy weather, when the relative humidity rises to 80% or more. Coated abrasives are often not given sufficient time to become equalized to the altered conditions during the transitional period, and therefore perform less than satisfactorily.

If the relative humidity increases, so does the moisture content of the backing and bonding of the coated abrasive.
Productivity and rate of output diminishes. The reduction can be between 50% to 100% with glue-bonded abrasives, and up to 25% with resin-bonded abrasives.

Coated abrasive backings (paper, cloth, fibre) respond to humidity changes at different rates than the bonding material (resin or glue). Consequently, the backing material alters in shape at a different rate than the bonding material. This difference causes overall distortion in the shape of the abrasive product. High relative humidity causes the coated abrasive to curl in a concave manner (grit side up). Low relative humidity causes the products to curl in a convex manner.

Additionally, damp air can cause the backing- to become "flabby," which in turn causes creasing, loading, and
premature grit loss (particularly glue-bonded products). Low humidity can cause product brittleness and lack of
flexibility.

Belt Handling Prior to Use
Abrasive belts, particularly wide belts, should be removed from the original packaging at least 24 hours prior to being used. The belts should be hung on special conditioning racks (easily fabricated) near the machine on which they will be run. This period will ensure that the belts have adjusted to ambient temperature and humidity conditions, as well as removing any "set" in the material from packaging. For wide belts, this conditioning is crucial.
A proper wide belt conditioning rack should have level hangers of at least 4" in diameter; preferably non-metallic, and at least 4" from the wall. The wide belts should hang so that they do not touch each other and are at least 1 foot off of the floor.

Hints For Belt Rack Construction- Coated Abrasive Safety Guidelines

1. Eye protection should always be worn when using any machinery-operated abrasive product (A.N.S.I. Standard Z87.1). Body protection should also be worn whenever appropriate; arm guards, leather gloves, and aprons. Loose clothing, jewelry, and hair should always be secured before using any powered machinery .
2. Machinery should always be maintained in good working order. Proper electrical controls should be easily reached and in good working order. Safety guards on machines should never be removed. Machinery should be disconnected from the power source before making any abrasive or machine adjustments.
3. Proper dust control is essential. Always observe OSHA regulations regarding dust collection. Dust masks are recommended to minimize dust inhalation. Dust collection systems should be properly maintained, and cleaned frequently.
4. Never use a coated abrasive product which is cut, creased, or otherwise damaged. Observe proper storage conditions.
5. Proper machinery use:
   • Always run lap joint belt in proper direction.
   • Jog the machine to start abrasive belt tracking, rather than full-power starts.
   • If unusual ticking or bumping noises are heard on a running abrasive belt, check belt and machine for possible damage.
   • On offhand applications, present the workpiece to the abrasive belt belo~ the center line of a contact wheel.
   • Proper belt tension should always be maintained.
   • Belt tracking should be properly adjusted.