Class Code 3831
Machine Shops – Aircraft Components
Class Code 3831 covers machine shops that manufacture, modify, or finish aircraft components—precision work on airframe and engine parts. The WCIRB pure premium for California effective Sept 1, 2026 is $2.819 per $100 of payroll; knowing this classification helps aerospace employers budget for workers' compensation and focus safety efforts where claims are most likely.
What Class Code 3831 Covers
This classification applies to shops whose primary business is precision machining, grinding, drilling, turning, milling, EDM, boring, and finishing of aircraft parts and subassemblies — for example, structural fittings, landing gear components, housings, and bearing journals. It includes both production and prototype runs, small contract manufacturers making parts to OEM print, and in-house aircraft component shops at MRO facilities when machining is the main operation. The work routinely involves tight tolerances, specialty aerospace alloys (aluminum, titanium, stainless steels), use of cutting fluids and coolants, tooling setup and fixture work, and final inspection and measurement using micrometers, gauges and CMMs. Repair, overhaul, and rework of aircraft components where machining is the dominant activity are also included under this code.
Who It Applies To
- Independent aerospace contract machine shops producing aircraft components
- In-house MRO (maintenance, repair, overhaul) shops that machine airframe or engine parts
- CNC machinists and operators working to aerospace tolerances
- Toolmakers and fixture builders for aircraft component production
- Quality control technicians performing dimensional inspection and NDT on machined parts
Common Job Duties
- Operating and programming CNC mills, lathes, and grinders to aerospace prints
- Setting up fixturing, jigs, cutting tools and offsets for precision runs
- Deburring, finishing, polishing, and surface-prep of machined components
- Using precision measuring equipment: micrometers, calipers, gauges, and CMMs
- Loading/unloading raw bar stock and finished parts; handling heavy components
- Mixing, applying, and disposing of cutting fluids and coolants; managing swarf
- Performing in-process inspection, recording measurements, and supporting NDT
Common Injury Risks
Understanding the $2.819 Rate
The pure premium rate of $2.819 per $100 of payroll represents the WCIRB's estimated loss cost for this classification — essentially the expected cost of claims before insurer expenses and adjustments. Employers multiply their payroll in this class by the rate (payroll/100 × 2.819) to get the base loss cost; the final premium your company pays will be adjusted by your insurer or PEO for experience modification, schedule credits/penalties, policy fees, state assessments, deductible programs, and any multi-class payroll mix.
Cal/OSHA Compliance Requirements
California employers must implement a written Injury and Illness Prevention Program (IIPP) and comply with Cal/OSHA requirements relevant to machining shops, including effective machine guarding, control of hazardous energy (lockout/tagout), respiratory protection where metalworking fluids or fine particulates are present, hazard communication for oils/solvents, and hearing conservation for high-noise areas. Regular training, equipment guarding inspections, ventilation for coolant mist, and documented maintenance/LOTO procedures are common Cal/OSHA expectations for these operations.
How Key HR Helps Employers Under Class Code 3831
A PEO like Key HR helps aerospace machine shops by ensuring correct classification and payroll allocation, delivering OSHA-aligned loss prevention programs (machine guarding, LOTO, hearing and respiratory programs), managing claims and return-to-work plans, and leveraging pooled purchasing for workers' comp and safety training. Key HR can monitor your experience modification, coordinate audits, and implement targeted loss-control measures that reduce claim frequency and the long-term premium impact.
Get a QuoteFrequently Asked Questions
How do I know if my shop should be classified under 3831 or another machine shop code?
Classification depends on the predominant operations. If your primary work is precision machining of aircraft-specific components to aerospace tolerances and you handle aerospace alloys, 3831 is appropriate. Shops focused on general metal fabrication, tool & die work, or assembly-only operations may fall under different WCIRB codes. Ask Key HR or your auditor to review payroll and operations for accurate classification.
What practical safety controls most reduce injuries and claims in aircraft machine shops?
Prioritize engineered controls: full machine guarding, automatic chip conveyors, guarding of rotating parts, local exhaust for coolant mist, and vibration-reducing tooling. Combine these with enforced LOTO procedures, PPE (eye, face, hearing protection), routine equipment maintenance, supervisor-led toolbox talks, and documented training tied to the shop's IIPP.
What steps can lower my workers' comp costs for this class?
Accurate payroll reporting and class allocation, proactive safety programs, early return-to-work/modified duty, disciplined claims management, and participation in group rating or experience-modification improvement plans all reduce costs. Partnering with a PEO like Key HR to implement targeted loss-control measures and to contest misclassifications or incorrect audits can materially lower your effective premium.
Quick Facts
- Class Code
- 3831
- Classification
- Machine Shops – Aircraft Components
- Pure Premium Rate
- $2.819 / $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 3831?
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