1. ABRASIVE WHEEL MACHINERY
This is an introductory slide. The presentation is not totally inclusive of all types of grinders. It is important to read and become familiar with the equipment before it is used. You should also be familiar with the Personal Protective Equipment (PPE) requirements. Usually, eye and face protection is required when using grinders/abrasive wheels.
These slides may be found in Tab 5 of the student notebook/handout materials.
The material was produced under grant number SH SH7 from the Occupational Safety and Health Administration, U.S. Department of Labor. It does not necessarily reflect the views or policies of the U.S. Department of Labor, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.

2. Objectives At the end of this session, the student should be able to:
Discuss the guarding requirements for different types of grinders
Review frequently cited hazards for abrasive grinding operations
Know how to test wheels for damage
Discuss the hazards of grinding wheels
Identify hazard controls and work practices to prevent injuries
This slide discusses the objectives for the training. It is important to become familiar with the hazards and methods to prevent injury. Always ensure the guard and safety equipment are in place. Employers should supplement this type of training with on-the-job, hands-on training on the equipment you will be using in the workplace.

3. What is Grinding?
Grinding involves the removal of materials through a process accomplished by abrasive particles that are contained in a bonded grinding wheel that rotates at a very high surface speed.
The rotating grinding wheel consists of many cutting teeth (abrasive particles) and the work is fed relative to the rotating grinding wheel to accomplish material removal.
Grinding is done when there is materials to removed from an object. The type of grinder will depend on how much marerial needs to be removed. Abrasive particles operating at high speeds usually create the grinding activitiy.

4. Hazards of Grinding Wheels
Grinding wheels move at a high rate of speed and can disintegrate and send flying debris for many yards
Eye injuries from flying debris
Abrasions, contusions, and lacerations from contact with wheel
There are numerous hazards associated with grinders, such as fire, eye injuries from flying projectiles, abrasions, contusions, and amputations from contact with the wheel.
Grinding is considered hot work, so you must consider the issuance of a hot work permit in areas that are set up for hot work. The action of grinding produces a lot of flying projectiles. Those particles can get in the eye and cause lacerations on the skin.

5. PPE for Grinding PPE needs to be used during grinding operations:
Face shield and safety glasses
Respiratory Protection
Gloves (Caution!)
Safety Boots
Hearing Protection
This slide discusses the importance of using PPE when grinding. Note the person in the picture is not using any PPE. Some of the PPE that is needed are the following items:
Eye and face protection,
hearing protection,
respiratory protection, and
safety boots.
Photo: a grinder in use with sparks flying from cutting surface and operator wearing no hand protection

6. Types of Abrasive Grinding Machines
Bench and floor stands
Surface grinders
Grinding flat surfaces
Swing frame grinders
Cylindrical grinders
Cutting off machines
There are many different types of grinders and each has a purpose. Some are designed to finish while other grinders are designed to remove a lot of materials. We will discuss each type in subsequent slides.

7. Grinders (Floor Model)
Floor stand model grinders are very popular and widely available for use. Some models even come with a ventilation system. The hood has to be built in accordance with ANSI standards to ensure the device has sufficient strength to contain the fragments of a shattered wheel.
Photos: Left side of slide shows a floor model grinder that is equipped with a ventilation system to capture the materials; Right side of slide shows a standard floor model grinder without ventilation.

8. Surface Grinder Examples
Point out the differences in the two pieces of equipment. The grinder has a table that moves, but note the barrier to the left of the wheel in the picture on the right. The barrier could possibly pose a hazard for workers. Employees could be struck by the barrier.
Photos: Left side shows a modern surface grinder w/adjustable table; right side shows an older model surface grinder

9. Surface Grinders Requirements
The surface grinder controls should be within easy reach of the operator.
Ensure the guard is in place and covers at least one- half of the wheel.
Check to make sure the magnetic chuck has been turn on and the materials are set up properly.
Make sure the anti-kick back device is in place.
Operator must ensure that all safety controls/features are in place before operating grinder.

10. Cut Off Grinders
Some machines are designed as cut off grinders. The grinder acts as a saw to cut through materials. On wheels mounted on saws, the spindle, nut, and flange are allowed to be exposed. Point these out on the photos.
Photos: The pictures illustrate a cut off grinder (L) and a grinding wheel mounted to a saw. (right)

11. Swing Frame Grinders
A swing frame grinder is a heavy duty surface grinder that is hanging by a chain that allows the operator to use the tool in any given direction. The tool is typically used in foundries and steel mills.
Photo source:
Photo: A worker is using a swing frame grinder to process all areas of the surface of a rounded piece of material. Employee should be wearing safety glasses.

12. Cylindrical Grinder
The application of a cylindrical grinder is to grind the outside. The cylindrical grinder can work on a variety of shapes, however the object must have a central axis of rotation. This includes but is not limited to such shapes as a cylinder, an ellipse, a cam or a crankshaft. Both the grinding wheel and the workpiece are moving.
Photo: A large cylindrical grinder.

13. General Requirements
The guards, per OSHA regulations, have to be on the machine except when:
Wheels are used for internal work
Portable operations with wheel two inches and smaller in diameter
Guards are usually required to be on grinders with few exceptions. The exceptions are very small wheels, less than 2 inches in diameter, and when the wheels are used for internal work.

14. Guard Design
The guard has to cover the spindle end, nut, and flange projections.
The cover over the spindle, nut, and flange can be omitted on cut off machines designed as saws
Mounted to maintain alignment with the wheel
Guard design specifications in ANSI B have been adopted
Guard design requirements.

15. What is the Hazard?
There are multiple issues with the guarding on this grinder.
Can you identify the issues?
The grinding has been done on the wheel face instead of the wheel periphery. Aluminum has also been ground on the wheel. The wheel is not to be used on aluminum because it clogs the pores that allow the wheel to breath. With clogged pores, the wheel can overheat and explode.
Photo: a grinding wheel that has been used incorrectly.

16. Wheel Alignment
What are the requirement to ensure the wheel maintains alignment with the guard?
To prevent the wheel from potentially shattering, the wheel has to be properly mounted. The wheel must be dimensionally accurate (flanges must has to maintain alignment). In order to maintain alignment, the flanges must be maintained (no sharp burs) and the flange should cover one-third of the wheel. The blotter (paper circle) is the area that is designed to distribute the forces of the flange.
Photo: a wheel being put on the machine. In the picture, you can see the blotter, flange, and the bolt.

17. Wheel Alignment Continued
Ensure the wheel is balanced. The wheel should be free of foreign substances.
The flanges must be geometrically accurate and maintained.
The tongue guard is not put on properly. It should be perpendicular to the wheel periphery. The bolt is not tightened properly and the flanges are not put on properly.
Photo: Grinder with alignment issues.

18. Work Rests on Bench Grinders
The work rests must be kept to within one-eighth of an inch of the wheel to keep the work from being jammed under the wheel and shattering.
Work rests have to be provided on all off hand grinders.
Workers must be trained to make the adjustment of the tongue guard and the work rest. The minimum adjustment of the guards are: one-quarter of an inch for the tongue guard and one eighth of an inch for the work rest. The manufacturer can require the guards to be set closer to the wheel.
Work rest have to be provided on all off hand grinders. An off hand grinder requires a worker to hold the piece of material.
Photo: Grinder with properly adjusted work rest. No tongue guards on the grinder.

19. Tongue Guards on Bench Grinders
The distance between the wheel periphery and the adjustable tongue must not exceed one-quarter inch.
The tongue guard is designed to contain the shattered wheel fragments.
The purpose of the tongue guard is to prevent the fragments from being thrown at the operator. The work rest is designed to keep the work from being jammed under the wheel.
Photo: (Top) Shows a properly adjusted work rest and tongue guard. (Bottom) Shows the measurement to check the adjustment of the tongue guard. Ask the class if it is correctly adjusted? NO, it measures over one inch away from the wheel!

20. Guarding Requirements for Grinders with Hoods for Ventilation
When a grinder is connected to a ventilation system, the hood has to be designed effectively to contain the fragments, in the event a wheel shatters.
The hood is a partial or complete enclosure around the wheel or disc through which air enters an exhaust system during operation. It is the dual function of grinding and abrasive cutting-off wheel hoods to protect the operator from the hazards of bursting wheels, as well as to provide a means for the removal of dust and dirt generated. The hood must meet the applicable strength requirements.
Photo: A hood or enclosure for a grinding wheel.

21. Guard Exposure Angles 29 CFR 1910.215(b)(2)
Type of Machine
Exposure Angle
Bench Grinder
90, 65 degrees above horizontal spindle
Cylindrical
180, 65 degrees above horizontal spindle
Surface Grinders
150, 15 degrees below the horizontal spindle
Swing Frame
180 degrees and top half enclosed
Snagging
180 deg., top enclosed
All grinders, especially those listed in the table have a maximum amount the wheel that can be exposed. The common grinders — bench grinder and surface grinder have maximum exposure angles.
The bench grinder has an exposure angel of 90 degrees 65 degrees below the horizontal spindle.
The surface grinder an exposure angle of 150 degrees, 15 degrees below the horizontal spindle.

22. Surface Grinders
The maximum exposure angle of surface grinder is 150 degrees
The wheel has to be guarded 15 degrees below the horizontal spindle
Discuss the exposure angel of a surface grinder. Note that the guard covers 15 degrees below the spindle.
Photo: surface grinder

23. Surface Grinders Continued
Ask the students “Can you spot the hazards in the picture?” The picture shows a shop with at least four surface grinders. Maintenance is being done on the machines, so the guards are out of position and it also appears that machines are not locked out or tagged out.
Photo credit:
Photo: shop with four surface grinders appears that maintenance is being done and there is no evidence that the machine is locked or tagged out.

24. Cut Off Grinder The top portion of the wheel must be totally enclosed
180 degrees of the wheel is allowed to be exposed
The picture shows a cut off grinder that has an upper hood that covers 180 degrees of the wheel. If the wheel is mounted to a saw, the spindle, nut, and flange may be exposed.
Photo: cut-off grinder

25. Swing Frame 180 degrees and top half enclosed
The top of wheel must be totally enclosed
This is a disconnected swing frame grinder that is no longer in use. Note the guard covers 180 degrees of the wheel.
Photo: a disconnected swing frame grinder

26. Portable Grinders Exposure angle will not exceed 180 degrees.
Top portion of the wheel has to be guarded
Only wheels two inches or smaller do not require a guard
Portable grinders are very hazardous due the wheel and the potential for the tool to kick back. Many portable grinders have a handle and the manufacturer states to maintain an athletic stance when using the tool.
Portable grinders typically have an exposure angle of 180 degrees.
Photo: Employee using a portable grinder with plume of sparks coming off the cutting surface.

27. Materials for Guarding 29 CFR 1910.215(b)(10)
Speed and type of wheel determine the type of materials:
Less than 8K SFM:
cast iron or malleable iron guards
More than 8K SFM:
cast steel or structural steel guards
Design must meet ANSI B
There are requirements for the construction of guards on grinders. The guarding has to meet the ANSI standard B , but usually the guards on newer machinery are built to the current ANSI standard.
Depending on the speed of the machine certain materials have to be used.
On low speed machines (less than 8K square feet per minute), the guards may be constructed of cast iron or malleable iron.
For high speed machines, a stronger materials would have to be used, such as cast steel or structural steel guards.

28. Frequently Cited Hazards
Missing or not adjusted tongue guard 29 CFR (b)(9)
Work-rests not provided and adjusted within one- eighth inch—29 CFR (a)(4)
Work rests are required on off hand grinders
Safety guards that cover nut, spindle, and flange 29 CFR (a)(2)
Safety guards—29 CFR (a)(1)
There are numerous hazards that cited by OSHA as related to the use of grinders in the workplace, such as:
Missing or not adjusted tongue guard—29 CFR (b)(9)
Work-rests not provided and adj. within one-eighth inch—29 CFR (a)(4)
Safety guards that cover nut, spindle, and flange—29 CFR (a)(2)
Safety guards—29 CFR (a)(1)
Guards are pretty easy to spot and the dimensions can be measured to see if a company is in compliance.

29. Frequently Cited Hazards
Ring test—29 CFR (d)(1)
A type of test that is performed before the wheel is mounted
Contact surface of wheel, blotters, flanges, flat 29 CFR (d)(3)
Exposure Angles—29 CFR (b)(2)
Flanges provided—29 CFR (a)(3)
Flanges are designed to maintain alignment of the wheel
There are numerous hazards that cited by OSHA as related to the use of grinders in the workplace, such as:
Ring test 29 CFR (d)(1)
Contact surface of wheel, blotters, flanges, flat 29 CFR (d)(3)
Exposure Angles 29 CFR (b)(2)
Flanges provided 29 CFR (a)(3)
These items are little more difficult to assess, but OSHA frequently will interview the machine operators to see if they understand the ring test.

30. Abrasive Wheels Organic wheels Inorganic wheels
Wheels are bonded with organic material (i.e., resin, shellac, or rubber
Inorganic wheels
Inorganic material (mineral)
Straight wheels, type 1
Grinding can only be done on the wheel periphery
Straight cup wheels, type 6
Grinding is done on the face (side)
Flaring wheel, type 11
Grind on the face (side)
There are many different types of wheels, such as the following:
Organic wheels are wheels which are bonded by means of an organic material such as resin, rubber, shellac, or other similar bonding agent.
Inorganic wheels are wheels which are bonded by means of inorganic material such as clay, glass, porcelain, sodium silicate, magnesium oxychloride, or metal. Wheels bonded with clay, glass, porcelain or related ceramic materials are characterized as "vitrified bonded wheels.“
Flaring wheels are used for consistent and quality grinding performance.

31. Methods to Test Grinding Wheels
There are two primary test methods:
Ring Test
Visual test using sand (Vibration)
This slide discusses the type of test that may be done before mounting the wheel. The ring test is mentioned in the OSHA standard where as the visual test using sand is not mentioned by OSHA.
Illustration: Graphic shows the wheel divided into four quadrants and arrows point to where the wheel should be struck with non-metallic tool. (Source: Idaho State University. Office of Workforce Training)
Source: Idaho State University. Office of Workforce Training

32. Ring Test Hold the wheel in a vertical position
Strike the wheel with a non-metal object
If the wheel creates the ringing effect it is in good condition
Crack will create a dead space
Inspection. Immediately before mounting, all wheels shall be closely inspected and sounded by the user (ring test) to make sure they have not been damaged in transit, storage, or otherwise. The spindle speed of the machine shall be checked before mounting of the wheel to be certain that it does not exceed the maximum operating speed marked on the wheel. Wheels should be tapped gently with a light nonmetallic implement, such as the handle of a screwdriver for light wheels, or a wooden mallet for heavier wheels. If they sound cracked (dead), they shall not be used. This is known as the "Ring Test.”
Photo: Shows a hand holding a grinding wheel while the other hand holding a tool conducts a ring test.

33. See what can happen?
The picture above shows what can happen when a wheel disintegrates at high speed. Note the pieces in the foreground and the damage to the office.
Photo: shows pieces of the grinding wheel scattered on the floor and damage/dents to the aluminum siding and a broken window on an office enclosure,

34. What is this?
The picture illustrates the aftermath of a wheel explosion. After this event, the company put a hood over the wheel to prevent the shattered wheel from being thrown throughout the facility.
Photo: close up of chunks of a grinding wheel

35. Wheel Disintegration
Note the tiny pieces of the wheel. These fragments can strike workers and cause serious injuries or death. Abrasive wheel grinders are everyday equipment in workplaces nationwide, many workers become complacent about their hazards. Improper use of a grinding wheel, or the use of one that is defective or damaged, can cause the wheel to break up.
Photo: illustrates a grinding wheel that has shattered or exploded.

36. Factors Contributing to Wheel Breakage
Improper mounting of the wheel
Excessive speeds
Abusive operation
Careless handling
Improper maintenance
Discuss the actions that may contribute to the breakage of the wheel many points under each factor.

37. Flanges are not properly matched Reversed flanges
Improper Mounting
Flanges omitted
Flanges are not properly matched
Reversed flanges
Improperly maintained flanges
Over-tightening the bolts
Mounting of the wheel is important to prevent it from shattering. If you omit the flanges, the wheel can’t maintain its proper alignment. In addition the flanges must be installed properly, the flanges have to be matched and put together properly. Flanges from time to time may need to be maintained to prevent sharp edges or burs.

38. Mounting of the Wheel
Care has to be exercised to ensure the wheel is mounted properly to maintain proper alignment.
It is very important to be familiar with the owners instructions and mount the right wheel for the machinery. The harbor should fit the grinding without too little or to much room.
Photo: Two workers mounting grinding wheel on grinder.

39. Mounting of the Wheel Continued
Flanges must be properly installed and maintained for alignment.
The speed limitations are posted on the side of the wheel and must be followed
Do not over-torque the bolts
This slide illustrates the proper techniques for mounting the wheel on the grinder. The worker is installing the flange and the bolts on the arbor of the grinder. Before mounting the wheel, you need to check to ensure the rating of the wheel is equal to or in excess of the machine rated speed. Make sure the blotter is on the wheel. If there is no blotter, do not use the grinding wheel.
Photo: Wheel being mounted with picture showing the flange and bolt as it is being placed on the spindle.

40. Flanges Flanges must be dimensionally accurate and in good balance.
There should not be any rough or sharp edges.
The graphic shows the spindle, nut, and flange. Flanges must be dimensionally accurate and maintained.
Graphic: spindle, nut and flange

41. Improper Speed Safety Criteria Grinding Wheel Speed
Ensure the wheel is designed for the speed of the machine
There are different types of wheels designed to be used at varying speeds (i.e., non-reinforced resin — 9500 SFPM and reinforced resin — 12,500+ SFPM)
Always ensure the wheel is rated for the machine or in excess of the machine. Pick and choose wheels that are designed for the machine. The wheel speed, in many cases, may be found on the blotter.
Photo: close up of label on grinding indicating maximum speeds for machine and wheels.

42. Improper Speed Continued
Converting low speed grinder to a high speed grinder, parts (spindle, guards, bearings) not rated for speed
Lack of speed control
Inadequate power to machine
develop flat spots
Improper speed can be a real problem for machinery. Improper speed can cause a lack of speed control and cause safety and quality problems with the use of the equipment. Never use a machine whose RPM is not known.

43. Abusive Action Grinding on the side of straight type wheel
Cramping of portable abrasive wheels
caused by putting stress on the side of a straight wheel
Grinding wheels should be used in a manner in which they are intended. Some wheels are designed work on the face; while other wheels are designed for work on the wheel periphery.

44. Careless Handling Setting the grinder down before it stops running
Physically check to make sure the wheel has stopped
Dropping the tool
Do not place tool in an area that it can be knocked off a table or bench
Improper storage
Store the wheel and tool in accordance with manufacturer specifications
Careless handling can be detrimental and cause the wheel to break apart. The tools need to be treated with respect in accordance with the manufacturer’s specifications.

45. Storage of Grinding Wheels
The picture illustrates the storage of grinding wheels.
Proper Storage of Grinding Wheels:
Never subject wheels to humidity, water or other liquids, freezing temperatures or sudden temperature changes.
Use suitable bins, drawers or boxes to store small wheels up to 4” diameter, together with cones, plugs, mounted points and wheels.
Cylinder wheels (type 18), straight cup wheels (type 6), dish wheels (type 27) and saucer wheels (type 28) should be stacked on flat sides with cushioning material between them.
Thick rim and hard grade cylinder and straight cup wheels may be stored on the periphery.
Store soft grade, straight cup wheels, and all taper cup wheels (type 11), base to base and rim to rim to prevent chipping of edges and cracking of walls.
Stack thin, plain wheels, such as cutting off wheels or saw sharpening wheels on a flat surface of steel, or similar rigid material.
Other plain or shaped wheels of appreciable thickness are best supported on the periphery in racks. To prevent the wheels from rolling the racks should provide cushioned, two point and cradle support.

46. Improper Maintenance
Guards are not adjusted and/or properly designed for the machine
Wheels are allowed to become rough due to improper dressing
Lack of inspection
Photo: picture shows a dressing tool.
Dressing tools are necessary to perform maintenance on grinding wheel. With use, grinding wheel will develop ridges. The tools can used to maintain the surface of grinding wheels.

47. Improper Maintenance Example
Note: The grinding wheel in the pictures needs immediate maintenance. Wheels with worn areas need to be dressed to restore the smooth wheel periphery.

48. Grinding Wheel Markings
A sequence of seven letters or numbers used to describe:
kind of abrasive, type, grain, grade, structure, bond type, marking to identify the wheel
Example Marking: 51-A-36-L-5-V-23
51: Optional for exact kind of abrasive
A: Abrasive type (i.e., al oxide or silicone carbide)
The slide discusses the wheel markings. It is important to understand the information to ensure that you are using the right type of wheel.

49. Grinding Wheel Markings (cont.)
Example markings: 51-A-36-L-5-V-23 36: Abrasive grain size (i.e., 36 medium), (6, coarse and 600, fine) L: Grade scale (A, soft-Z, L= medium) 5: Structure (0, dense; 16+, open) V: Bond type: (i.e., R-rubber, V-vitrified) 23: Manufacturers’ wheel identity
The slide discusses the wheel markings. It is important to understand the information to ensure that you are using the right type of wheel.

50. OSHA Accident Investigations
Seven of 27 accidents investigated involved fatalities caused by wheel disintegrations (26%)
Seven injuries occurred as the result of grinding wheels disintegration (26%)
Six injuries were due to amputations (22%)
Discuss the type of injuries that audience has seen associated with the use of the equipment. [What year are these accident data from? Should include.]

51. Damaged Grinder
Photo: Grinder on the floor of a facility; missing a handle.
This picture illustrates a grinder that was involved in a fatality. The guard was on the grinder, but the operator did not have control over the tool. The tool kicked back and hit the operator in the head causing a fatality.
Note it is missing the handle. Most tools come with a handle to allow the operator to maintain control of the tool, Most manufacturers require the operator to maintain an athletic stance when using the tool.

52. Grinders Exercise #1—Hazard Hunt
For this exercise, you are going to look at the following slides. From the pictures, be prepared to discuss the following:
What are the hazards in the slide?
How would you correct the issues or the problems that you see in the slides?
Explain the goals of the hazard hunt exercise. Students will be shown four slides of grinders with hazards and they should be prepared to discuss them and how to correct them.

53. Hazard Hunt 1
The plastic shield over the bench grinder has no relevance on the machine guarding. The plastic is not adequate for machine guarding and does not meet the manufacturer requirements for a spark guard. Note the missing guard on both sides of the grinder.

54. Hazard Hunt 2
Photo: grinder that is not mounted and is missing work rest and tongue guard.
This is an ugly picture as the picture illustrates a grinder that is not mounted and the work rest and tongue guard are not installed. The wire brush would actually be noted as a violation of (General Machine Guarding). The wire brush needs the complete guard plus a work rest.

55. Hazard Hunt 3 Photo: Grinder with spark guard in place
Spark guard is in place, but it does not serve as a substitution for eye and face protection.

56. Exercise #2—Mounting the Grinding Wheel
In your groups, brainstorm to determine the steps to mount an abrasive grinding wheel. Include the following steps:
Correct sequence of events
Steps for safety
The answers should include the following:
Inspect and conduct "a ring test" to look for damages before mounting a wheel. Compare the machine speed to the speed marked on the wheel before mounting the wheel. Never exceed the speed marked on the wheel.
Disconnect machines from their power source before you begin mounting or removing wheels.
Check the flanges for distortion or abrasion. When flanges are distorted or warped, the contact area is reduced. Flanges must not be reversed.
Use blotters to cushion flange pressure. Do not use flat washers, a nut, old blotters or other filler materials in place of flanges. This set-up will not support the wheel but rather it will damage the wheel and cause the wheel to wobble, pull out the bushing, and break. The fixed and loose flanges should have the same diameter and have undercut relief. The minimum flange size is 1/3 of the wheel diameter.
Thread the wheel on the machine and hand tighten. Don't use power tools to put the wheel on, as removal will be difficult and the wheel can be damaged. Make sure that all surfaces between the wheel, blotters, and flanges that should be in contact with each other during mounting are flat and free of foreign particles. The wheels must fit freely on the spindle.
Test wheel and machine by running it at operating speed in a protected area at least one minute before grinding.