Preventing Bench Grinder Accidents – Today’s Medical Developments
Because bench grinders are everyday machines in workplaces nationwide, many operators are becoming complacent about their risks. However, bench grinders are very dangerous when used improperly. Statistics show that more than half of crusher injuries, such as fingers caught in the machine or eye and face lacerations, are the result of operator error. Rockford Systems LLC, a leading provider of machine guarding products and services, offers this primer on grinder safety regulations to help prevent accidents.
First of all, it is important to be familiar with the regulations that describe the installation, maintenance and safe operation of the grinder. The workplace regulations that apply to shredders are OSHA 29 CFR SubPart O 1910.215, a “machine specific” (vertical) regulation with a number of requirements that, if left unchecked, are often cited by OSHA as violations. ANSI B11.9-2010 (grinders) and ANSI B7.1 2000 (abrasive wheels) also apply. Read these sets of regulations carefully before using a grinding machine.
Rest and Tongue Guard
OSHA specifies that work supports must be kept snug within 1/8″ of the wheel to prevent the workpiece from being pinched between the wheel and the support, resulting in potential wheel breakage. Because grinders run at such high rpm, the wheels actually explode when they break, causing very serious injuries, blindness and even death.In addition, the distance between the wheel and the adjustable tongue guard – also called -spark” – should never exceed 1/4”. As the impeller wears during use, these two dimensions should be regularly checked and adjusted.
Grinder safety gauges can be used when installing, servicing and inspecting bench/pedestal grinders to ensure that work supports and tongue guards comply with the OSHA 1910.215 and ANSI standards. To do this, wait until the grinding wheel has come to a complete stop and the grinder is properly locked out before using a grinder safety gauge. The grinder slowing down time takes several minutes, which may tempt an impatient employee to use the gauge while the wheel is still spinning. This practice is very dangerous because it can cause wheel breakage.
Another tip: when it comes to grinders, personal protective equipment (PPE) usually means a full face shield, not just safety glasses. The fact is that an employee cannot be too careful with a machine that is operating at several thousand revolutions per minute. Remember to document all safety requirements set forth by OSHA as this is the best evidence that safety procedures are being followed.
OSHA requires that grinding wheels be tested before mounting. This simple step prevents the inadvertent mounting of a cracked wheel. Ring-testing consists of hanging the wheel by its central hole, then tapping the side of the wheel with a non-metallic object. This should produce a bell sound if the wheel is intact. A clunking sound or cracked plate noise indicates a cracked wheel. For larger grinders, the grinding wheels are laid flat on a vibrating table with sand evenly distributed over the grinding wheel. If the wheel is cracked, the sand moves away from the crack.
To avoid cracking a wheel during the mounting procedure, employees must be very carefully trained in these procedures. It starts with making sure the wheel is properly matched to that particular grinder, using the correct blotters and spacers, and knowing exactly how much pressure to apply with a torque wrench, to name a few things.
This OSHA compliant wheel cover allows no more than a total of 90° degrees of the wheel left exposed. (65° from the horizontal plane to the top of the trim). Never exceed these maximum trim opening dimensions. Larger wheel cover openings create a wider pattern of flying debris in the event of a wheel explosion.
A well-known safety precaution on bench/pedestal grinders is to stand well beside the grinding wheel for the first full minute before using the machine. Accidents have shown that grinding wheels are more likely to break/explode during this first minute. OSHA Instructional Standard #STD 1-12.8 dated October 30, 1978 deals with conditional and temporary removal of work support for use with larger workpieces only, provided side guards are provided.
grinder to do
- Always handle and store wheels with care
- Visually inspect all wheels prior to assembly for any damage
- Make sure that the operating speed of the machine does not exceed the speed marked on the wheel, its blotter or its container
- Check that the mounting flanges are of equal size, relieved as needed and of correct diameter
- Use mounting blotters when supplied with wheels
- Make sure the work support is set correctly on pedestal and floor grinders
- Always use a safety guard that covers at least half of the wheel
- Allow newly mounted wheels to run at operating speed, with guard in place, for at least one minute before grinding
- Always wear safety glasses or an approved type of eye protection while grinding
- Turn off the coolant before stopping the wheel to avoid creating an out of balance condition
Do not grind
- Do not use a wheel that has been dropped or appears to have been abused
- Don’t force a wheel on a machine or change the mounting hole size – If a wheel won’t fit the machine, buy one that will
- Never exceed the maximum operating speed established for the wheel
- Do not use mounting flanges whose bearing surfaces are not clean, flat and smooth
- Do not overtighten the mounting nut
- Do not grind on the side of conventional, straight or type 1 wheels
- Do not start the machine until the safety guard is properly and securely in place
- Do not block the work in the wheel
- Do not stand directly in front of a grinding wheel whenever a grinder is started
- Do not grind materials for which the wheel is not designed
Rockford Systems offers a wide variety of grinder guard products including motor starters, disconnects and shields.