NAICS 333131

Overview

The North American Industry Classification System (NAICS) is the U.S. government’s standard for organizing establishments to produce consistent economic statistics. Developed with Office of Management and Budget oversight and first implemented in 1997 to replace SIC, it is updated on a five‑year cycle; the latest vintage is 2022. NAICS was created jointly by the United States, Canada, and Mexico to enable cross‑country comparability. ¹

NAICS 333131 covers establishments primarily engaged in manufacturing underground mining machinery and equipment (for example, coal breakers, mining cars, core drills, coal cutters, rock drills) and manufacturing mineral beneficiating machinery used in surface or underground mines. Surface mining machinery is classified in 333120, and well‑drilling machinery is classified in 333132. ²

See also on G2X:

• NAICS 333120
• NAICS 333132

What this NAICS covers

• Underground mining machinery and equipment manufacturing (e.g., coal cutters, rock drills, core drills). ²
• Coal breakers and pulverizers manufactured for underground mining applications. ²
• Mining cars and related underground haulage equipment. ²
• Mineral processing and beneficiating machinery designed for mine use (surface or underground). ²
• Underground drilling machinery specifically engineered for mining. ²
• Equipment assemblies integrating multiple metal‑forming and complex assembly processes typical of machinery manufacturing for mining. ²

Related NAICS and PSC codes

Type	Code	Descriptor
NAICS	333120	Construction Machinery Manufacturing (includes surface mining machinery; underground mining machinery is excluded to 333131). 2
NAICS	333132	Oil and Gas Field Machinery and Equipment Manufacturing (includes well‑drilling machinery; underground mining drills are in 333131). 2
PSC	3820	Mining, Rock Drilling, Earth Boring, and Related Equipment. 3
PSC	3805	Earth Moving and Excavating Equipment (construction/mining equipment category). 3

Cross‑references and exclusions from official NAICS text

• Surface mining machinery and equipment are classified in 333120. ²
• Well‑drilling machinery is classified in 333132. ²
• Coal and ore conveyors are classified in 333922. ²
• Underground mining locomotives are classified in 336510. ²

SBA small business size standard

• The SBA small business size standard for NAICS 333131 is 900 employees (employee‑based measure), effective March 17, 2023. ⁴

Frequently asked questions

• What activities are included in NAICS 333131?

  • Establishments manufacturing underground mining machinery (such as coal cutters, rock drills, core drills, mining cars) and mineral beneficiating machinery for mine use. Examples and scope are defined in the official NAICS text. ²

• How does NAICS 333131 differ from 333120 and 333132?

  • 333131 is for underground mining and mineral beneficiating machinery. Surface mining machinery falls under 333120, while oil and gas field (and water well) drilling machinery is covered by 333132. ²

• Are conveyors and mining locomotives part of 333131?

  • No. Coal and ore conveyors are classified under 333922; underground mining locomotives are classified under 336510. ²

• What is the SBA size standard for small business eligibility under 333131?

  • SBA’s size standard is 900 employees for NAICS 333131. This employee‑based threshold is used for set‑asides and other federal small business programs. ⁴

• What NAICS vintage is currently being implemented in federal economic statistics?

  • The Census Bureau began releasing detailed industry statistics using the 2022 NAICS and plans to complete adoption across economic programs by the end of calendar year 2027, with a few survey exceptions that follow later. ⁵

Useful resources

• U.S. Census Bureau — NAICS 2022, Manufacturing sector text (includes 333131 definition and cross‑references). ²
• Census — Implementation of the 2022 NAICS (timeline and program adoption). ⁵
• Census — NAICS reference files (2022 NAICS descriptions). ⁶

References

1. U.S. Census Bureau — About Industry (NAICS overview, 1997 adoption and five‑year updates including 2022): https://www.census.gov/topics/employment/industry-occupation/about/industry.html
2. U.S. Census Bureau — NAICS 2022, Manufacturing (31‑33) archive text (includes 333131): https://www.census.gov/naics/resources/archives/sect31-33.html
3. Acquisition.gov — DFARS PGI Part 208 (PSC listings including 3805 and 3820): https://www.acquisition.gov/dfarspgi/pgi-part-208-required-sources-supplies-and-services
4. U.S. Small Business Administration — Table of Small Business Size Standards (effective March 17, 2023): https://www.sba.gov/sites/default/files/2023-06/Table%20of%20Size%20Standards_Effective%20March%2017%2C%202023%20(2).pdf
5. U.S. Census Bureau — Implementation of the 2022 NAICS: https://www.census.gov/library/reference/code-lists/naics/2022/implementation-timeline.html
6. U.S. Census Bureau — Industry Reference Files: NAICS Descriptions (2022–2023): https://www.census.gov/programs-surveys/nonemployer-statistics/technical-documentation/reference/naics-descriptions.html