Safety

Grinding Machine Maintenance

21 Jun 2023

Proper Grinding Machine Maintenance is Critical to Ensure Safe Grinding Wheel Usage

ANSI B7.1 states: An employer shall maintain grinding equipment in a condition that will not create a hazard for an employee. The employer shall instruct an employee to report defective equipment to an employee supervisor. In the event of a wheel breakage, the grinder shall be inspected and returned to safe operating condition before being returned to service.

Be sure to follow the machine supplier’s recommended maintenance schedule. The machine should also be visually inspected before every use. Checks should include, but are not limited to:

Unauthorized alterations
Guards (present, correct, and in good condition)
Bent or damaged spindles
Electrical cord or air hose condition
Attached auxiliary handle (if using an angle grinder)
Any other signs of damage or abnormalities

In addition to regular maintenance and visual inspections, the machine speed needs to be verified according to a schedule defined by ANSI B7.1. Before going into further detail on that, let us make it clear, EVERY time a wheel is mounted or remounted onto a machine, the operator must check the wheel and machine's speed to ensure the wheel is not operated in an over-speed condition. The abrasive wheel's safe operating speed is marked on the wheel, and the machine's normal operating speed is marked on the machine. NEVER exceed the wheel's safe operating speed as stated in Revolutions Per Minute (RPM) or Surface Feet Per Minute (SFPM). Failure to comply with this requirement is very dangerous and a violation of ANSI safety requirements and OSHA law.

ANSI B7.1-2017 has the following requirements for when machine speed must be checked.

7.1.5 Speed Check of Machines - User's Responsibility (The Requirement)

The user shall establish a program to ensure that grinding machines do not subject abrasive wheels to speeds greater than the maximum operating speeds marked on the wheel or package. In the case of variable speed machines, the number of revolutions per minute (RPM) may be increased as the diameter of a wheel is reduced through wear, provided the original surface feet per minute (SFPM) is never exceeded (the speed table in section 9, table 28 will help convert RPM to SFPM, also see section 1.3.78, page 11). It shall be the user's responsibility not to exceed these maximum operating speeds. Spindle speed shall be measured at the free running speed of the machine and verified with the proper use of a tachometer or stroboscope.

E 7.1.5 Speed Check of Machines - User's Responsibility (Explanation of the Requirement)

Portable air grinders must be checked to ensure the proper air pressure is maintained and that the machine governor mechanism is clean, in good operating condition, and functioning properly. This reference to air grinders is not intended to overlook the necessity for a regular check of the speed of the wheel spindles on all types of grinding machines. The user should assign this responsibility to competent personnel using equipment properly designed for speed checks, such as a tachometer or stroboscope. The user should also keep a permanent record of such speed checks.

A tachometer is suitable for most machines to check the spindle speed (RPM). From a safety standpoint, this tachometer check should be made without the grinding wheel, loose flange, or nut mounted on the spindle.

ANSI B7.1 defines the frequency of speed measurement by machine type per the following:

Illustration 78 - Frequency of speed measurement for various machine types
Measure Speeds at Time of Installation of All Machines

Portable Grinders
1. Air Driven	Measure the speed of governor controlled grinders every 20 hours of actual use of once per week, whichever comes first. Measure speed of all types of grinders after maintenance or repair, whenever a grinder is issues from the tool crib and at each wheel change. Several readings should be taken.
2. Electric Driven (Hi-Frequency)	Measure monthly and after any maintenance or repair that could affect the speed of the machine.
Stationary Grinders
1. Direct Drive (Single Speed)	Measure after any maintenance or repair that could affect the speed of the machine.
2. Belt Driven (Single Speed)	Measure monthly and after any maintenance or repair that could affect the speed of the machine.
3. Variable Speed Machines	Measure once per week and after any maintenance or repair that could affect the speed of the machine. On variable speed machines, other than semi-automatic snagging grinders, measure speed whenever a wheel change is made.

Knowing and following the ANSI/OSHA rules will keep you safe at the wheel! We hope all your grinding wheel usage is safe and productive.

For more information on grinding wheel safety, read our Proper Mounting of a Grinding Wheel, Starting a Grinding Wheel, and When is a Grinding Wheel Worn Out? articles.

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