Revision Date: July 1, 2025
Contents
2. Controls by Shop Safety Level
3. Risk Group Classification System of Tools
1. Overview
This procedure supports Policy 4302 Student-Access Shop and Tool Safety Policy and provides guidance for determining the applicable controls and Risk Group applicable to Tools based on their Shop Safety Level (“SSL”) Classification.
2. Controls by Shop Safety Level
A Shop’s classification is determined by the highest hazard level of any Tool in the Shop. However, for the purpose of Tool Use Restrictions and Oversight, the Shop’s hazard classification can be temporarily lowered when all higher-hazard Tools are securely locked out or physically restricted from use.
Shop Supervisor: A Shop Supervisor is a staff or faculty member assigned by the Shop’s department to supervise activities. They must complete the required safety training and have professional-level training and experience in Tool set-up, use, and maintenance.
Shop Monitor: A Shop Monitor is a Graduate Student (or higher rank) designated by a Shop Supervisor to oversee Shop activities. They must complete the required safety training and have sufficient Tool and Shop experience. The Shop Monitor has full authority over Shop use when the Shop Supervisor is not present.
| Shop Safety Level | SSL-2 | SSL-3 | SSL-4 |
|---|---|---|---|
| Shop Access Control | By permission of Shop Supervisor and/or Monitor | ID card required for access to all Student-Access Shops | ID card required for access to all Student-Access Shops |
| Tool Use Restrictions and Oversight |
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| User Training |
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| Monitor and Supervisor Training |
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| Emergency Shut-Offs | Room-level emergency shut-offs (EPOs) for electrical power to Risk Group (RG) 4 tools | ||
| Tool Access Controls |
Locked cabinet (Tool key / code lockout for laser or thermal foam cutters) |
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*Graduate Students working in SSL-4 Student-Access Shops must have either a Shop Monitor or Shop Supervisor present unless all Graduate Students in the Shop have met the necessary qualifications, training, and experience to be certified as Shop Monitors for that specific Shop. In cases where all Graduate Students are certified as Shop Monitors, they may work under a Machine Shop Partner System, provided they adhere to all other safety protocols and have received explicit permission from the Shop Supervisor.
3. Risk Group Classification System of Tools
Tools are categorized into four Risk Groups, ranging from Risk Group 1 (lowest risk) to Risk Group 4 (highest risk). The risk classification considers the likelihood of injury and the potential severity of that injury, referred to as residual risk. Residual risk accounts for the risk that remains after considering built-in safety measures (engineered mitigations).
Several factors affect the risk associated with each tool, including:
- Type of Tool: Manual or powered (e.g., electric, pneumatic, liquid fuel, hydraulic, or powder-actuated).
- Power Tools: The force or power the user may be exposed to (e.g., horsepower, RPM, vibration).
- Activation Mechanism: Sequential or non-sequential start.
- Hazard Type: Common hazards (e.g., poor maintenance, sparks).
- Operational Complexity: How difficult the Tool is to set up and operate.
- Mitigation Methods: Standard safety features (e.g., guarding, PPE, anti-restart mechanisms, emergency shut-offs) and their effectiveness.
- Injury Potential: Types of injuries typically associated with the Tool (e.g., cutting, crushing, kickback) and the likely severity of those injuries.
This classification provides a general framework for grouping common Tools. However, EHS and/or the Shop Safety Committee has the authority to impose additional safeguards and precautions for specific Tools based on their unique risk factors. If a Tool is not listed in the provided classification table, contact EHS for assistance in determining its appropriate Risk Group.
| Tool Risk Group | Risk Description | Types of Injuries | Typical Risk Factors | Common Examples |
|---|---|---|---|---|
| RG-1 | Low | Minor injuries such as small cuts, scrapes, or bruises; injuries are generally superficial and often result from mishandling or improper grip. |
Tools are unlikely to cause injury if used properly. Basic safety training and minimal PPE, such as gloves or safety glasses, are typically sufficient. Can often be used without direct supervision. General Risk Factors: 2-4 amp @ 120 VAC, <9V cordless |
Dremel tool, cordless drills under 18V, palm sanders, soldering irons, heat guns, hot melt glue guns, sewing machines, manual hand tools, 3D printers |
| RG-2 | Moderate | Moderate injuries, such as deeper cuts, abrasions, punctures, or minor fractures, are possible. Repetitive strain or soft-tissue injuries may occur if used improperly over time. |
Potential for moderate injury if not used correctly. Requires specific safety training, standard PPE, and sometimes additional safety features. General Risk Factors: ¼ to ½ hp, <10 amp @ 120 VAC, <24V cordless, specialized enclosed CNC tools + see RG 1 for other risk factors to consider. |
Jig saw, 3/8” hand drill, corded devices < 1/3 hp, 18V-24V cordless drill, benchtop/manual tools, laser cutters, thermal foam cutters, waterjets, manual printing presses |
| RG-3* | High | Severe injuries, including major lacerations, fractures, crush injuries, amputations, or severe burns, are possible with improper use. |
Tools have moving, sharp, or heavy parts capable of inflicting serious harm. Can be used safely with advanced training, PPE, and direct supervision. Often involves larger machinery with built-in safety features. General Risk Factors: >½ hp, 10-15 amps @ 120 VAC, 24V-36V portable, pneumatics, hydraulics + see RG 1-2 for other risk factors to consider. |
Circular saw, belt sander, framing nailer/stapler, ½ hp geared drill, reciprocating saw, > 24V cordless tools, chop/miter saws, routers, mini-lathe, angle grinders, printing presses (Vandercook), bandsaws (excluding resaw applications), small drill press, small milling machines, small metal lathes, woodturning lathes, belt/disc sander, horizontal saw, scroll saw, planer, jointer, surface grinder, bench grinder, iron worker, Saw Stop-style table saw only, Powered Platen Style Printing Presses |
| RG-4 | Extreme | Very severe injuries, including life-threatening trauma, extensive crush injuries, major amputations, or severe burns. |
Tools involve high speeds, sharp blades, heavy machinery, or hazardous materials. Requires specialized training, dedicated safety features, and enhanced supervision. General Risk Factors: Typically large, powerful equipment capable of causing extreme injuries based on national injury statistics + see RG 1-3 for other risk factors to consider. |
Manual and CNC-controlled: Full sized milling machine, Full sized metal lathe, Radial arm saw, Large drill press, Resaw bandsaw, Large jointer/planer, Shaper/molder, Power shear, Chainsaw, Table saw without Saw Stop |
NOTE: * For Tools in RG-3 the Shop Supervisor should consider individual instruction that includes one-on-one assessment of the user, task, & Tool.
Notes
1Material covered will include background information about Yale’s shop safety program, monitor/supervisor roles and responsibilities, machine safeguarding, general chemical safety, emergency response procedures, and fire prevention and response.
Related Resources
4302 Student-Access Shop and Tool Safety Policy
4302 FR.01 Acknowledgement of Shop and Tool User Roles and Responsibilities
4302 FR.02 Acknowledgement of Shop Supervisor and Monitor Responsibilities