Class Code 3840
Auto, Truck Or Motorcycle Parts Mfg
Class Code 3840 covers employers who manufacture parts for automobiles, trucks, or motorcycles — from stamped sheet-metal components and machined engine parts to welded assemblies and heat-treated gears. The California pure premium rate for this classification is $5.085 per $100 of payroll, which reflects the loss experience for machining, stamping, forging and related shop operations. Accurate classification matters because operations with heavier machinery, hazardous processes or poor safety programs will drive higher costs through claims and experience modification.
What Class Code 3840 Covers
This classification applies to businesses whose primary operation is manufacturing motor-vehicle parts: machining (CNC turning and milling), metal stamping, die-casting, forging, heat treating, grinding, welding and assembly of components such as gears, shafts, brake parts, brackets and housings. It includes on-site finishing processes commonly used in parts plants—plating, coating and limited paint booths—as well as machining of castings and forgings. Shops performing prototype tooling, small-batch production, or contract manufacturing for OEMs and aftermarket suppliers fall under 3840 when the work is primarily fabrication and parts production. Routine vehicle repair, parts distribution/wholesale, body shops, and retail tire or battery service are excluded and classified separately.
Who It Applies To
- CNC machinists and setup/operators in a parts manufacturing shop
- Press and stamping machine operators at a stamped-component plant
- Welders, brazers and metal-fabrication assemblers producing vehicle parts
- Heat-treat technicians and furnace operators processing gears and shafts
- Quality inspectors and test technicians working on finished parts
- Maintenance mechanics and electricians servicing production machinery
Common Job Duties
- Programming, setup and operation of CNC mills, lathes and turning centers
- Operating stamping presses, shears, blanking equipment and hydraulic presses
- Grinding, deburring and finishing parts using bench grinders and abrasive tools
- Performing welding, brazing, brazing or filler-metal joining of components
- Heat-treating, quenching and tempering metal parts in furnaces
- Material handling with forklifts, overhead cranes and manual lifting during staging and assembly
- Routine machine maintenance, tool changes and lockout/tagout procedures
Common Injury Risks
Understanding the $5.085 Rate
The pure premium rate of $5.085 per $100 of payroll is the insurers' base cost reflecting expected claim costs for this class. To calculate the base workers' comp premium, multiply your payroll for employees assigned to 3840 by 0.05085. Insurers then add expense loads, policy adjustments and apply your companys experience modification; those factors and payroll classification accuracy determine the final premium you pay.
Cal/OSHA Compliance Requirements
California employers in parts manufacturing must maintain a written Injury and Illness Prevention Program (IIPP) under Cal/OSHA Title 8 and comply with hazard communication and chemical safety requirements (Hazard Communication/GISO). Machine guarding, control-of-hazardous-energy (lockout/tagout), respiratory protection, hearing conservation and hot-work/welding controls are commonly required depending on operations. Employers should also ensure trained forklift and crane operators, confined-space procedures for tanks and pits, and documented training/recordkeeping to meet Cal/OSHA inspection standards.
How Key HR Helps Employers Under Class Code 3840
A PEO like Key HR helps businesses in this class reduce workers' comp costs through accurate payroll reporting and correct class-code assignment, coordinated claims management, and sustained return-to-work programs. Key HR can deliver loss-control consulting, targeted shop-floor training (machine guarding, LOTO, welding fume controls), and aggregated buying power for insurance, all of which help lower claims frequency and improve your experience modification over time.
Get a QuoteFrequently Asked Questions
Does Class Code 3840 include vehicle repair shops or mobile mechanics?
No. 3840 is for manufacturing parts. Repair garages, mobile mechanics and vehicle service operations are assigned different California class codes; employees who only service or repair vehicles should not be reported under 3840.
What practical steps lower my workers' comp premium in a parts plant?
Key actions include formal machine-guarding audits, a written IIPP with documented training, lockout/tagout procedures, a respiratory and hearing-conservation program where needed, proactive maintenance to prevent failures, and an early-return-to-work policy to reduce claim severity.
How should I allocate payroll if employees do multiple tasks?
Payroll should be assigned to the class code that most accurately reflects each employees primary duties. For mixed duties, track actual hours by task and report payroll pro rata so your premium reflects the true exposure; a PEO can help set up time-tracking and proper reporting.
Quick Facts
- Class Code
- 3840
- Classification
- Auto, Truck Or Motorcycle Parts Mfg
- Pure Premium Rate
- $5.085 / $100 payroll
- Effective Date
- September 1, 2026
- Source
- WCIRB Approved Filing
Manage Workers' Comp Through a PEO
Key HR provides pay-as-you-go workers' comp for California employers — no large deposits, no audits, better rates.
Get a Quoteor call (800) 922-4133Ready to Simplify Workers' Comp for Class Code 3840?
Key HR provides California employers with pay-as-you-go workers' comp, HR compliance support, and payroll — all through one PEO partnership.