Video Transcript
Abrasives are one of humanity's oldest and most versatile tools. They have shaped the future for centuries, and continue in that role today in the creation of sophisticated information age components.
While they remain one of our most widely used and reliable tools, improper use is still a serious problem. Failure to follow these procedures can result in serious injury or death. A failed wheel can be just as lethal as a bullet.
Of course, the general rules covered in this video cannot cover all questions or situations. Please refer to ANSI B7.1 for additional safety information.
Careful wheel storage and handling are the foundation of every grinding safety program. All incoming grinding wheel containers must be inspected.
Damage doesn't have to be obvious to be dangerous. If there is any visible evidence of damage to the container, the shipment should not be accepted.
All grinding wheels are breakable. They must be handled with special care to prevent damage. Never drop or bump a wheel into an object, and never roll a wheel like a hoop.
Review and follow the safety warning found on the box, in the box, and on the grinding wheel. Wheels should be stored in racks, as shown here and outlined in Section 2 of ANSI B7.1. Please note that the front and back of the rack are designed to protect the grinding wheels from accidental bumping.
Storage locations must also protect wheels from exposure to water, any temperature or humidity conditions that cause condensation on the wheel, and freezing temperatures. Stock should always be rotated so that the oldest grinding wheel is used first.
Grinding wheel storage at the workplace is just as important as long‑term storage. When a grinding wheel is not mounted, it must be stored on a properly designed rack. Remember, damage doesn't have to be obvious to be dangerous.
Before mounting any grinding wheel, it must be inspected. All grinding wheels are tested and inspected by Norton Company, as per ANSI B7.1. Damaging treatment is always possible, however, between our plant and your machine. Never take that chance. Inspect all wheels before using them.
First, visually inspect the wheel. Never use a wheel that shows any signs of damage, such as chips, cracks, or gouges. Then, ring‑test it. Never use a grinding wheel that does not ring true.
Please note that due to the composition of some of our super‑abrasive and resin wheels, they cannot be ring‑tested. Ring‑testing works best with vitrified, bonded grinding wheels. For more information, see ANSI B7.1.
Grinding wheels are designed for grinding machines. There are no exceptions. Never mount grinding wheels on table saws, radial arm saws, milling machines, sanders, electric motors, routers, or any machine not designed, guarded, and approved for grinding wheels.
Never mount a grinding wheel on a machine like this.
The grinding wheel you choose must also be rated for the grinding machine you use. Before mounting a wheel on any grinder, be sure that the speed of the wheel is rated at or below the speed rating of the wheel.
Each time you mount a grinding wheel, clean and inspect all flanges. Grinding wheel flanges drive the grinding wheel, and must have sufficient contact area. They must also be the proper type, the proper size, be matched, relieved, flat, and free of foreign particles and burrs.
If flanges are not uniform in diameter and contact area, they will set up dangerous cross‑bending stresses when tightened. Worn, distorted, or warped flanges may cause the grinding wheel to slip, or may set up dangerous stress concentrations that cause the wheel to break.
Grinding wheel flanges used in precision applications must be at least one‑third of the grinding wheel's diameter.
Another method of checking flanges uses a fluid specifically designed to detect flange imperfections. The flange is first thoroughly coated with the fluid.
It is then applied to the wheel and rotated. If the flange is distorted, or there are any high spots on the flange, the fluid will be rubbed off in those areas, identifying the imperfection.
Repeat this process for both flanges. If the flanges are distorted, they must be replaced or repaired.
The process of actually mounting the wheel begins by placing a new, clean blotter on the flange. Slide the wheel onto the arbor, making sure that it fits freely. If the fit is tight, get a new wheel.
Never force a wheel onto a flange or arbor. If you do, you may damage the wheel or its hole, and destroy the carefully engineered clearance between the wheel and the arbor. If the arbor heats up and expands, the wheel may break.
If the wheel has a "mount up," "mount down," or "top" stenciled on it, make certain the wheel is mounted in the direction indicated.
Make sure that neither blotter folds over into the wheel's hole, or is bunched up under the flange. A blotter in this condition can set up dangerous stresses and cause a wheel to break.
The next step is to properly tighten the flanges. The order of tightening and the torque setting are both critical to proper grinding wheel mounting.
Maximum permissible applied torque is dependent on flange design and material. Therefore, you must always follow the machine manufacturer's recommended torque requirements. Under tightening can lead to slip. Overtightening can lead to dangerous wheel damage.
If the torque requirement is unknown, contact the machine builder. This information plate, for example, is located on the centerless machine, and clearly instructs the user on the recommended torque requirements, and the order of tightening.
If the flanges are worn, sprung, warped, or the threads of the screws or tapped holes are not in good condition, and you reduce the torque used, the wheel may slip. If this occurs, replace or repair flanges, screws, and retapped holes as needed, to provide adequate threads.
Also, retightening may be required after the wheel has been in use, or if blotters shrink due to grinding coolant or normal compression. For more information on mounting wheels with multiple screw mounts, see ANSI B7.1.
When mounting a wheel using a single end nut, it must be tightened just enough to prevent the wheel from slipping during use.
When more than one wheel is mounted between a single set of flanges, and they are not cemented together or separated by spacers, the wheels must be specifically manufactured to be used in sets.
Never mix wheels on your own. The wheels shown here are manufactured and tested to be used together as a set. Always mount wheel sets with stripes properly aligned.
Once the wheel is placed on the machine, lock the guard in place.
Run the grinding wheel for one full minute with the wheel guard in place, with no one standing in front of or in line with the wheel.
Even after performing the proper wheel inspection, this will give you an important added measure of safety. If the wheel has hidden damage, it will most likely break within the first minute at operating speed.
With a safe wheel properly mounted, you then need to consider wheel balance. Proper wheel balance will improve the product performance and part quality.
This creep feed machine has a precision balance adjustment device. On the many machines without this capability, however, wheel balance must be achieved in other ways.
This usually means dressing or truing the wheel. In this case, the operator is dressing a diamond wheel with an aluminum oxide dressing stick.
Another method, shown here, is the static balance adjustment. To avoid out‑of‑balance conditions when grinding with coolant, be sure to turn the coolant off before turning off the machine. Allow the coolant to run out of the wheel before stopping the wheel.
Finally, when you begin to grind, take care never to jam or bump the wheel into the workpiece. If you do, change the wheel. Never use a damaged wheel.
Every grinding machine has its own set of specific safety procedures. The bench and pedestal machine is no exception. It is one of the most common grinding machines in service today. We'll take a moment now to review some of its specific safety considerations.
We have already reviewed the mounting procedure for single end nut machines, but there are many other safety measures you should be aware of, and use.
Before working on any grinding machine, be sure to lock and tag the machine to prevent accidental startup.
Proper adjustment of the tongue guard and work rest is critical to operator safety. In the event of a wheel breakage, the tongue guard can help to protect the operator from injury by helping to contain broken pieces within the guard system.
The opening in the tongue guard must be no more than one‑quarter inch. The opening in the tool or work rest must be set at no more than one‑eighth inch. If this opening is too large, objects may fall into the machine, causing a wheel to break.
Always grind on the proper surfaces of the wheel. Do not grind on the side of the wheel. Excessive side pressure from side grinding can cause the wheel to break.
Also, be sure to grind using the proper wheel. Use an aluminum oxide wheel for ferrous metals, and a silicon carbide wheel for non‑ferrous metals.
Dress grinding wheels often. Don't load or fill up the wheel's grinding surface or face.
Remember that a bench grinder that is properly guarded can prevent an injury if the grinding wheel is broken. This wheel was intentionally damaged to demonstrate the effectiveness of these wheel guards.
Always wear safety glasses and other appropriate personal protective equipment when working within the grinding area.
Grinding generates dust. Most of it comes from the material being ground. Excessive dust inhalation can be hazardous. To avoid breathing problems, always employ dust controls and/or protective measures appropriate to the material you're grinding.
Please review the Material Safety Data Sheet, MSDS, for the grinding wheel, work material, coolant, or any other product used in the grinding process. For more information, refer to Federal Communications Standard 29 CFR 1910.1200 and ANSI Z9.6.
Grinding, if done correctly, is a safe and reliable process, one that has been developed and refined for more than 100 years, but failure to follow safety procedures can result in serious injury or death.
The major causes of grinding wheel accidents today can be traced to simple mistakes. Using the wrong wheel or machine, careless handling, improper mounting, over speed, and not paying attention in general.
To help prevent accidents, become familiar with the do's and don'ts of grinding. Always follow the safety warning found on the box, in the box, and on the grinding wheel. Remember, the general rules covered in this video cannot cover all questions or situations. Please refer to ANSI B7.1 for additional safety information.