Coated Abrasive Fiber Disc Safety

Roger E. Cloutier, Senior Product Safety Engineer
Saint-Gobain Abrasives, Inc.

 

Coated abrasive discs have an excellent safety record with few reported disc breakages and personal injuries. However, breakages and personal injuries should and can be prevented. As with most accidents, operator error is a major factor, following established safety rules will reduce the probability of any such occurrences. Please review and follow the safety tips listed below.

 

Coated Abrasive Fiber Disc Storage:

Temperatures and humidity are the two very important factors influencing coated abrasive performance and safety. Improper or inadequate storage can damage discs making them unsafe. Backings and adhesives are sensitive to climate changes and will gain or lose moisture according to the relative humidity of their surroundings.

Excessive humidity may cause the fiber backing of a disc to absorb excessive moisture. This increase in moisture may cause the disc to curl up (convex shape like a taco shell) called cupping. Discs that are cupped or curled up should never be used. A disc in this condition may snag on the work piece causing it to break. Another potential hazard of is that excessive moisture could cause the adhesive bond to soften and cause the disc to suddenly shed or loose large amounts of abrasive grains.

Excessive dryness may cause the disc to curl or arch down in a concave manner and become brittle and lose flexibility. In short, high and low humidity's can cause concave and convex cupping respectively. See examples below:

"The Good" "The Bad" "The Ugly"  
  

  

   

To keep your disc flat and safe please follow the list of the proper storage requirements for coated abrasive discs:

  • Store abrasive disc at 40-50% relative humidity and 60-80 degrees F (15-29 degrees C).
  • Coated abrasive disc must be stored at least four inches (10 or more centimeters) above the surface of concrete floors, away from open windows, out of direct sunlight and away from heat sources such as radiators, steam pipes, and air conditioner exhaust vents.
  • Protect coated abrasive discs from exposure to water or other fluids/solvents.
  • Always follow any abrasive manufacturer's storage instructions.
  • Never use hooks when handling or transporting coated abrasive containers.
  • Do not drop or in any way damage the coated abrasive packaging.
  • If packaging is received damaged, the product inside must not be used. Return any damaged product to its manufacturer.
  • Rotate stock, use on a first-in, first-out basis.
  • Store coated abrasive discs in their original packaging.

 

Another major cause of disc breakage and injury can be traced back to equipment problems. Using the wrong grinder/sander, failure to use the correct back-up-pad, jamming or catching the disc on the work piece, and excessive operating speeds are all leading causes of disc breakages and must be avoided.

 

Below is a check list that will help you to eliminate some of these problems:

 

  • Never run a coated abrasive disc on an unfamiliar machine without obtaining and following machine instructions.
  • Select the proper grinder or sander for the job. Abrading heavy amounts of material from a work piece may require a grinder, while for light sanding or blending a sander may result in personal injury. A tool that is too small or underpowered can result in such problems as forcing the machine and abrasive disc causing the disc to slip, snag, or break.
  • Match the coated abrasive disc and back-up pad to the machine. For example, never use a 9" coated abrasive disc or back-up pad on a 5" sander.
  • Review and follow all of the machine manufacturer's recommendations.
  • Review and follow all of the fiber disc manufacturer's recommendations.
  • Before mounting a disc or for any type of machine repair, disconnect the grinder/sander from its power source, thus eliminating the possibility of the machine accidentally starting during mounting or repairing operations.
  • Check sander/grinder spindle for run-out. If there is any run-out (wobble) in the tools spindle, repair or replace as needed.
  • Inspect the back-up pad on the machine. Never use a coated abrasive fiber disc without a back-up pad that is the correct size, (remember: maximum disc overhang is 1/4"), shape, free of irregularities such as fractures (cracks), excessive wear, nicks, cuts at the edges or in the center hole. Check the back-up for concentricity.
  • NEVER exceed the speed rating (marked in RPM) of a back-up pad.
  • Never use another disc as a back-up pad.
  • Never use a disc without a back-up pad.
  • Never alter the size or shape of an abrasive disc.
  • Never alter the size or shape of a back-up pad.
  • Check disc retainer nut for thread wear. Also check for snug fit and full three-point contact except when using quick change or non-wrench systems.
  • Use proper disc mounting equipment. Never use adhesives to fasten discs to back-up pads.
  • Never use a coated abrasive disc with nicks, cuts, tears or any other visible damage.
  • Only use a disc that fully contacts the back-up pad. Never use a warped disc.
  • If a grinder is used or if the sander is equipped with a guard, the guard must be used. Never remove a guard provided by the machine manufacturer. Guards prevent injuries and are highly recommended.
  • Many air driven sanders, such as pistol grip air sanders, are un-governed machines. Therefore, as many with all pneumatic tools, air regulars must be used at each work station. The speed of the sander is determined by the air pressure provided to the tool. If the machine is designed to operate at 20,000 RPM at 90 PSIG and the air pressure is allowed to exceed 90 PSIG, the speed of the machine can go up exponentially. NEVER MOUNT A BONDED GRINDING WHEEL ON A PISTOL GRIP AIR SANDER!
  • If you selected an electrical power tool, make sure you are using the correct voltage. Never attach a sander/grinder designed for a 110 volts into a 220 voltage power source. Take all normal electrical tool precautions.
  • Electrical cords or air hoses should be checked regularly for cracks and worn areas.
  • Check with the manufacturer of the materials you are going to grind for special grinding and handling instructions. If you are grinding combustible or other hazardous materials, check these instructions for any special fire containment equipment, extinguishing materials, or other special requirements.

Personal protective equipment is an important "safe guard" available to the operators and bystanders of coated abrasive operations. Using the proper safety equipment can save eyes, limbs, hearing, and help prevent future respiratory problems.

 

Always use the proper PPE list below:

 

  • Face-shield
  • Gloves
  • Safety shoes
  • Arm guards
  • Apron
  • Long pants
  • Eye protection (Must wear a face-shield with eye protection)
  • When required use a dust mask or approved respiratory tract protection appropriate for materials being abraded or ground.
  • Hearing protection (required when the operators are exposed to noise levels exceeding the established threshold levels).

How you use the grinding system can determine the safety for you and your co-workers. Always comply with the following safety rules:

 

  • The tool must be starts just off the work-piece and must be brought up to full operating speed before beginning grinding or sanding.
  • Always ease the disc into the work piece at 5-10 degree angle to the work piece surface,
  • Look for and avoid any areas on the work piece that the disc may become caught on or jammed.
  • When grinding depressions, moldings, lips, and heavy welds, move the grinder away from the work area and not into it.
  • A disc used for heavy stock removal shall not be allowed to rest flay upon the work piece. If this action is allowed, the whole tool assembly may be thrown into a rough, jumpy mode.
  • Jamming or snagging the edge of the disc on the sharp edge or jagged surface of a work piece should be avoided. Instead, the disc should be worked down gradually into the jagged surface before allowing the edge of the disc to bite into it. Excessive punishment of the disc's edge will break even the strongest coated abrasive disc.
  • When grinding or sanding small movable work pieces, the work pieces must be secured to prevent the work pieces from moving when the coated abrasive makes contact with them.
  • Grind or sand in well ventilated areas.
  • Direct sparks away from your body and away from bystanders.
  • Do not grind near flammable materials.
  • Do not wear loose fitting clothing.
  • Do not store or rest the grinder/sander on the disc and pad.
  • Do not place grinder/sander down until the disc has stopped rotating.
  • If the grinder/sander is dropped, replace back-up pad and disc before using.
  • Avoid body or any other unintended contact with rotating disc or back-up pad.
  • If chatter or vibration occurs during use, stop the tool at once. Determine the cause of the problem and correct before continuing.
  • When using a non-round shaped disc and back-up pad avoid tight corners and any place where the non-round disc can catch.
  • If using an AVOS disc (with scooped holes), do not start the equipment with an object protruding through the scooped holes in the product.
  • Do not stick objects in the scooped holes while mounting or in use.
  • Follow all the safety rule set by your employer, governmental agency or others in authority.

 

If you comply with the above instructions and use the greatest safety tool of all, "Common Sense" you can prevent disc breakages and injuries.

Read  Setting Standards: Part 1 and Setting Standards: Part 2 for more about product safety.

 

For additional information on this topic or if you need any other abrasive safety information, please review ANSIOSHA and all literature provided by the abrasive wheel and machine manufacturer. You may also contact the Saint-Gobain Product Safety Department at Tel: (508) 795-2317 or Fax: (508) 795-5120 or contact your Saint-Gobain Abrasives, Inc. representative with any safety related questions.