Safe practices improve precision grinding results.

Manufacturers in all industries are constantly improving the quality standards of their products. That means ever-tighter demands on the tolerances of their metalworking operations. The tolerance of the final finish depends in large part on the precision grinding wheel. Used properly, the precision grinding wheel is a highly productive and safe tool for today's metal-working plant.

Grinding wheels have an excellent safety record, the result of 80 years of research and exhaustive testing by wheel manufacturers. However, it would be a mistake for operators to become complacent about grinding wheels; for the well-being of the operator and the quality of the final product, safe handling and use is critically important.

Safe operation depends largely on the treatment to which the wheel is subject during use. Abrasive manufacturers pride themselves on supplying grinding wheels that are as safe and effective as possible. It is up to the user to follow important safety precautions in the storage, handling, and use of a grinding wheel to keep potentially dangerous occurrences to an absolute minimum.

Wheel storage, handling

All incoming grinding wheel containers must be inspected. If there is visible evidence of damage to the container, the shipment should NOT be accepted. Grinding wheels should NEVER be shipped unpacked or loose. Operators should NEVER accept a grinding wheel that is not shipped in a package.

Despite the best efforts of the manufacturer, however, all grinding wheels are breakable. Care must always be used in the handling of grinding wheels to prevent damage. Wheels should never be dropped or allowed to bump into an object and they should not be rolled (hoop fashion).

Grinding wheel storage at the workplace is very important. When a grinding wheel is not on its machine, it must be stored properly and protected. Wheels should be stored in racks that feature an enclosure designed to protect the grinding wheels from accidental bumping. Grinding wheels must be stored to avoid such hazards as:

Exposure to water: Any temperature or humidity conditions that cause condensation on the wheel.

Freezing temperatures: Stock should always be rotated so that the oldest grinding wheel is used first. Norton Co recommends that grinding wheels be used within two years of their manufacture date.

Wheel Inspection: Just prior to mounting a grinding wheel, all wheels must be inspected. Norton Go and other manufacturers test and inspect all grinding wheels before they are shipped. After they leave the manufacturer's site until the time you receive them, it is possible that they may have been damaged. Never take that chance; always inspect all wheels before using them.

First, visually inspect the wheel for cracks or other signs of damage. Never use a wheel that shows chips, cracks, gouges, or other signs of damage. If the wheel appears sound, the next step is to "ring test" it. Tap the side of the wheel with the handle of a wooden mallet or the handle of a screwdriver, and notice if it gives a clear ring. Never use a grinding wheel that does not ring true. Because of the composition of some super-abrasive and resin wheels, they cannot be ring tested. Ring testing works best with conventional abrasive vitrified (glass-type) bonded grinding wheels.

Mounting the wheel

The machine you use for grinding should be properly designed for that purpose. 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.

After the wheel is inspected, the speed of the grinding wheel must be checked to make sure the machine's speed is at, or below, the speed of the grinding wheel.

All grinding wheel flanges must be cleaned and inspected each time a grinding wheel is mounted. The grinding wheel flanges drive the grinding wheel and must have sufficient contact area. They must be of the proper type and size, be matched, relieved, flat, and free of foreign particles. If flanges are not uniform in diameter and contact area, they will create dangerous cross-bending stresses when tightened. Worn and distorted or warped flanges may cause the grinding wheel to slip or break. Grinding wheel flanges used in precision applications must be at least 1/3 the grinding wheel's diameter.

One method for checking the flatness of a wheel flange is to use a straight edge. A straight edge placed on the bearing surface of a flange near the mounting screws must not rock and can be checked with a feeler gauge for a more exact measurement.

Another method of checking flanges is to use ink. The ink is applied to the flange, the flange is applied to the wheel, and is then rotated. If the flange is distorted, the ink will be removed or rubbed off on the high spots. Repeat this process for both flanges. If the flanges are distorted, they must be replaced or repaired.

Never force a wheel onto a flange or arbor. This can damage the wheel or its hole. It can also destroy the wheel's carefully constructed clearance between the wheel and the arbor. If the arbor heats up and expands, the wheel may break.

Select the proper wheel for the job--for example, an aluminum oxide wheel for ferrous metals and silicon carbide abrasive for non-ferrous metals.

Using the wheel

Once the wheel is placed on the machine, lock the guard in place. Run the wheel for one full minute with the guard in place. Be sure that no one is standing in front of or in line with the wheel; if the wheel was damaged in handling and storage, it will most likely break within the first minute of rotation at operating speed.

Never jam or bump the wheel into the workpiece. If the wheel is bumped into the workpiece accidentally, it may become damaged, and should be discarded. Proper wheel balance will improve the product's finish and reduce the possibility of grinding wheel damage. Wheels must be dressed to ensure that they are running true and when the wheel's face is loaded with the material being ground. When grinding with coolant, allow the coolant to run out of the wheel before stopping the wheel to avoid creating an out-of-balance condition.

Before any wheel changes, guard adjustment, or any type of repair work on any grinding machine, be sure to lock and tag the machine to prevent accidental start-up. For machines used in off-hand applications, proper adjustment of the tongue guard and work rest is critical to the operator's safety. In the event of a wheel breakage, the tongue guard can help to protect the operator from injury and must be properly set. The opening in the tongue guard (the space from the grinding wheel to the guard) must be no more than 1/4". An opening larger than 1/4" may allow large pieces of broken wheel to escape the wheel guard and cause injury.

The opening in the tool or work rest must be set at no more than 1/8". If this opening is too large, objects may fall into the machine, causing the wheel to break. Always grind on the proper surfaces of the wheel; do not grind on the wheel's side. Excessive side pressure caused by side grinding can cause the wheel to break.

Dust warning

Proper steps must be taken to prevent breathing problems while grinding. Before grinding begins review the Material Safety Data Sheet (MSDS) for the grinding wheel, work material, coolant, or any other product used in the grinding process. During the grinding process, grinding wheels or other products may emit or generate a hazardous dust, fume or vapor. Excessive airborne concentrations may result in irritation to the eyes, skin, and respiratory tract.

Always use adequate ventilation, dust controls, personal protective equipment, and all other appropriate equipment and procedures for the grinding process. It is the owner's and the user's responsibility to determine the suitability of a product or particular use. Check all applicable industry, federal, state, and local regulations and warnings carefully before using grinding wheels.

Grinding dos and don'ts

Follow these general guidelines for improved grinding wheel safety:

DO ensure that guards and work rests are properly adjusted and secure before starting the machine.

DO use a safety guard covering at least one-half of the grinding wheel.

DO wear protective safety glasses and additional eye and face protection if required.

DO dress the wheel or make grinding contact gently.

DO re-dress the wheel when necessary.

DO turn off the coolant before stopping the wheel to avoid creating an out-of-balance condition.

DON'T exceed the maximum operating speed established for the wheel.

DON'T start the machine until the guard is in place.

DON'T force grinding so that the motor slows noticeably or the work gets hot.

DON'T allow stationary wheels to rest in fluid.

DON'T apply pressure to wheels to stop them.

DON'T continuously use glazed wheels without dressing.

DON'T use wheels for purposes other than those for which they are designed.

Precision grinding FAQs

Is a grinding wheel a dangerous tool?

No -- if the wheel is properly mounted and not abused, it is not dangerous.

Can grinding accidents be serious?

Definitely. In use, the periphery of a grinding wheel usually travels at a speed faster than a mile a minute. If the wheel should break while traveling at that speed, serious personal injury or damage to machinery or equipment might result.

What causes grinding wheel accidents?

In most cases, they are due to carelessness or lack of knowledge. The most common causes are using the wrong wheel for the job; careless handling; improper mounting; excessive speed; and excessive pressure.

What can I do to prevent such accidents?

First, have a general understanding of the strength of various types of wheels. Second, learn how to mount the wheel properly. Third, learn how to grind so there will be no danger of damaging the wheel. Fourth, always use proper guarded machines designed for the grinding wheel and the work being done.

Are all grinding wheels equally strong?

No; they are all breakable, but some kinds of wheels may actually be ten times stronger than others. Some wheels are quite brittle; the bond in vitrified wheels is similar to glass and can be easily broken. Resin bonded wheels are tougher and can stand harder usage.

Why can't we use only the strong, tough wheels?

These wheels are not suitable for all types of grinding. For some jobs, relatively soft wheels are necessary to prevent burning and spoiling sensitive and expensive work materials.

How do I know which wheel to use for my job?

Use only the kind of wheel that has been designated by your supervisor or someone in authority. As a check, the tag or blotter on the wheel shows the highest speed recommended by the wheel manufacturer, never exceed the wheel's rated speed. Never borrow a wheel from another job; it might not be the right kind of wheel for your lob.