OSHA 1910.215(a)(1)(iii) — Exception: Cones, Plugs, and Threaded Hole Pot Balls Where the Work Offers Protection
OSHA 29 CFR 1910.215(a)(1)(iii) establishes an exception to the standard machine guarding requirement for certain small abrasive wheel types—specifically Types 16, 17, 18, 18R, and 19 cones, plugs, and threaded hole pot balls—used in operations where the workpiece itself provides effective protection.
These wheel types are typically small, compact shapes designed for internal or recessed grinding, finishing, and smoothing surfaces in tight or confined areas.
Regulatory Text
“Types 16, 17, 18, 18R, and 19 cones, plugs, and threaded hole pot balls where the work offers protection.”
Purpose and Intent
The intent of OSHA 1910.215(a)(1)(iii) is to acknowledge that certain abrasive wheel shapes and applications naturally provide protection through the workpiece’s geometry.
When these specialized wheels are used within recesses, cavities, or internal spaces, the surrounding material acts as a natural guard, effectively containing the wheel and preventing operator contact or fragment ejection.
Applicable Wheel Types
- Type 16: Straight-sided cones used for heavy-duty snagging and rough grinding in confined areas.
- Type 17: Tapered cones designed for grinding fillets, corners, and curved surfaces.
- Type 18 and 18R: Plug wheels with a round or oval face, often used for smoothing foundry castings or deburring holes.
- Type 19: Threaded hole pot balls with a spherical or cup-like shape used for inside radius or concave surface grinding.
Conditions for the Exception
- The wheel must be one of the specified types (16, 17, 18, 18R, or 19).
- The operation must occur within or against a workpiece that surrounds the wheel sufficiently to act as a barrier.
- The workpiece must fully or partially enclose the wheel, preventing the operator from direct contact.
- If the workpiece does not offer full protection, a supplementary guard or shield must still be used.
- The wheel must be properly mounted on a threaded mandrel or arbor and secured per manufacturer instructions.
Common Applications
- Foundry finishing: Removing risers, burrs, and rough edges from castings.
- Weld dressing: Smoothing and blending weld beads in confined areas.
- Maintenance grinding: Cleaning and polishing internal surfaces of equipment housings or pipes.
- Die and mold repair: Finishing cavities or internal contours.
Safety Considerations
- Ensure the workpiece provides complete coverage of the wheel during operation.
- Use tools that are rated for the wheel’s maximum safe operating speed (MSOS).
- Inspect each wheel for cracks, looseness, or improper thread engagement before use.
- Wear appropriate eye and face protection (OSHA 1910.133) and hand protection to guard against debris.
- Maintain a firm grip and control of the tool to prevent kickback or misalignment in tight areas.
Hazards Controlled
- Fragment ejection: The workpiece confines debris and fragments if the wheel fails.
- Contact injury: The geometry of the task and the workpiece acts as a barrier against operator contact.
- Overexposure to rotating parts: Only a minimal portion of the wheel is exposed during use.
- Loss of control: Reduced risk due to the small size and low mass of these wheel types.
Best Practices for Compliance
- Verify that the workpiece truly provides protection before applying this exemption.
- Use tools equipped with side handles or vibration-dampening grips for better control.
- Follow ANSI B7.1 guidelines for cone and plug wheel installation and use.
- Train operators to recognize when an additional guard or shield is required.
- Inspect the threaded hole and mandrel for wear or cross-threading before installation.
Why OSHA 1910.215(a)(1)(iii) Is Important
OSHA 1910.215(a)(1)(iii) allows flexibility for operations using specialty cone, plug, and pot ball wheels by recognizing situations where traditional guards are redundant.
These wheel types are designed for use in recessed areas where the workpiece inherently restricts exposure to moving parts.
However, the exemption places responsibility on the employer to ensure that the work truly offers protection and that operators maintain proper PPE, inspection, and mounting practices.
Related Standards
- OSHA 1910.215(a)(1): General machine guarding requirements for abrasive wheels.
- OSHA 1910.215(b): Detailed guard design and exposure limitations.
- ANSI B7.1: Safety code for the use, care, and protection of abrasive wheels (includes specifications for cone and plug types).
- OSHA 1910.243(c): Portable powered tool safety requirements.
FAQ
Why are cone and plug wheels exempt from standard guards?
Because they are used inside recesses or cavities where the surrounding workpiece already provides physical protection from contact and debris.
Does this exemption apply to all cone or plug wheels?
No. It applies only to Types 16, 17, 18, 18R, and 19, and only when the workpiece itself provides sufficient coverage to act as a guard.
Is PPE still required under this exemption?
Yes. Operators must still wear proper eye, face, and hand protection, as the exemption removes only the guard requirement—not the need for personal protective equipment.
