Bolt, Nut, Screw, Rivet, and Washer Manufacturing (U.S., NAICS 332722)

1. Overview

This is the business of making the small metal parts that hold nearly everything together: bolts, nuts, screws, rivets, washers, studs, and other industrial fasteners. It is a foundational, unglamorous manufacturing industry — a modern car contains thousands of these parts, and a passenger jet contains millions — yet the whole U.S. manufacturing side employs fewer people than a single large retailer.[1]

Why an investor should care: fastener demand is a clean read on the real economy. Because fasteners go into cars, buildings, machinery, and aircraft, orders rise and fall with industrial production, auto builds, construction starts, and aircraft delivery rates. It is a cyclical, commodity-exposed business at the low end and a high-margin, hard-to-enter engineered business at the high end (aerospace and specialty alloys) — two very different economics under one industry code.

Ways in: there is no pure-play U.S.-listed fastener manufacturer of scale. Public-market investors reach the industry mostly through diversified industrials that own fastener units (Illinois Tool Works, Howmet Aerospace, Nucor), through fastener distributors (Fastenal, W.W. Grainger), through one small direct manufacturer (Chicago Rivet & Machine), or through foreign-listed pure-plays. Private investors reach it through a large field of family-owned regional manufacturers and private-equity roll-ups. Details are in Sections 4 and 10.

2. What it is and how it's structured

Scope. NAICS (North American Industry Classification System) code 332722 covers establishments that make metal bolts, nuts, screws, rivets, washers, and other industrial fasteners using forming machines such as headers, threaders, and nut-formers.[16] The core production process is cold heading — feeding steel, stainless-steel, aluminum, nickel-alloy, or titanium wire into a machine that hammers a head onto a blank at high speed, then rolling threads onto it. Parts may then be heat-treated, cleaned, plated or coated, inspected, sorted, and packaged. The National Fastener Distributors Association identifies cold and hot heading, screw machining, thread rolling, grinding, heat treatment, and plating as the principal production methods.[17] Output ranges from commodity Grade-2/5/8 hardware store bolts to titanium and nickel-superalloy aerospace fasteners.

What it excludes (adjacent codes). The classification captures domestic manufacturing only, and even within manufacturing it draws tight lines:

• 332721 Precision Turned Product Manufacturing — parts machined on screw machines/lathes (not cold-headed) fall here, not in 332722.[16]
• 326199 All Other Plastics Product Manufacturing — plastic fasteners belong in this code, not 332722.[16]
• 332618 Other Fabricated Wire Product Manufacturing and 332613 Spring Manufacturing — wire forms and springs.
• Wholesale distribution (NAICS 42x) — Fastenal, W.W. Grainger, and thousands of fastener distributors are not in 332722; they buy and resell, they don't forge.
• Imported fasteners — most fasteners consumed in the U.S. are made abroad and never touch a domestic 332722 plant (see Section 3).

That boundary matters: many commercial "fastener market" reports combine manufacturing, distribution, plastic clips, anchors, precision-machined parts, and installation tools that Census does not include in 332722.

Ownership mix. The domestic manufacturing base is highly fragmented and mostly private: family-owned regional shops, private-equity-backed roll-ups, and fastener divisions inside larger public industrials. Only a small slice sits inside U.S.-listed companies, and usually as one segment of a diversified parent. The Industrial Fasteners Institute represents more than 160 member companies across the United States, Canada, and Mexico.[18]

3. How big it is

Our federal figures describe the domestic manufacturing industry:

Concentration is very low. The four largest firms account for just 18% of revenue, the top eight 29.6%, and the top 50 about 67.4%; the Herfindahl-Hirschman Index (a standard 0–10,000 concentration score) is only 160.2 — well inside the range regulators treat as unconcentrated.[2] In plain terms: hundreds of small manufacturers, no dominant player on the standard-fastener side. Chicago Rivet, itself a small public manufacturer, states that no single company dominates its industry and that it competes against both independent manufacturers and divisions of large industrial groups.[19]

The undercount caveat that matters here is not tiny operators — it's imports and distribution. The ~$12.9 billion of domestic shipments badly understates U.S. fastener consumption. Independent market research puts the total U.S. fastener market (which includes imported product and the distribution markup) at roughly $23.6 billion in 2024, projected above $29 billion by 2030.[4] The gap is filled by imports: Taiwan supplies about a third of U.S. fastener imports (~$2.3 billion) and China nearly a fifth (~$1.3 billion), with Japan next.[5] Fastenal, the largest fastener distributor, notes that most of its suppliers are outside North America.[20] So domestic manufacturing is a minority of the fasteners Americans actually use — a critical fact for reading this industry's true size and its exposure to trade policy.

4. The investable universe

There is no large U.S.-listed company whose only business is making fasteners. Public exposure comes in three flavors: (a) diversified industrials with a fastener unit, (b) aerospace-fastener specialists, and (c) distributors. Tickers, prices, and multiples below are for orientation only.

Public companies with meaningful fastener manufacturing:

Note on recent divestitures: Stanley Black & Decker sold its STANLEY Engineered Fastening aerospace business (Consolidated Aerospace Manufacturing) to Howmet in 2026.[21] TriMas Corporation sold its aerospace-fastener segment (Monogram, Allfast, Mac Fasteners, TFI Aerospace) to PennAero in March 2026 for about $1.45 billion — at roughly 18x EBITDA, showing what a quality specialty-fastener asset commands.[9] Neither company retains direct aerospace-fastener exposure.

Foreign-listed pure-plays (for investors who want direct exposure): LISI S.A. (Euronext Paris, aerospace and auto fasteners), Bossard Holding and SFS Group (SIX Swiss Exchange), Bufab AB (Nasdaq Stockholm), and Bulten (Nasdaq Stockholm) are dedicated fastener manufacturers/distributors with no large U.S.-listed equivalent.

Distributors (proxy exposure, not manufacturers): Fastenal (FAST, Nasdaq) and W.W. Grainger (GWW, NYSE) are the cleanest large-cap ways to bet on fastener volume, though they distribute rather than forge; Distribution Solutions Group (DSGR, Nasdaq) owns Lawson Products.

Major private and PE-owned manufacturers: MW Components (owned by American Securities), which acquired Elgin Fastener Group in 2023;[12] MacLean-Fogg, a notable private North American automotive and industrial fastener manufacturer;[24] Optimas OE Solutions; PennAero (backed by Tinicum and Blackstone, now holding the former TriMas Aerospace brands);[9] and a long tail of family firms — Birmingham Fastener, Portland Bolt, Cold Heading Company, Buckeye Fasteners, PennEngineering, and Omni Fasteners.

5. How the money works

Owners make money by turning metal wire into finished fasteners and capturing the spread between what they pay for input metal and what they charge for the part — but the quality of that spread depends entirely on where a shop sits on the commodity-to-specialty ladder.

The core economics:

• Input cost is the swing factor. The main raw material is cold-heading-quality (CHQ) steel wire rod; for wire-based metal producers, raw material can run 80–90% of operating cost.[25] Howmet lists aluminum alloys, nickel alloys, stainless steels, conventional steels, titanium alloys, and energy among the principal inputs to its Fastening Systems segment.[22] Fastener makers pass steel moves through via surcharges, but margins get squeezed when the metal spikes faster than they can reprice.
• Volume absorbs fixed cost. Cold-heading lines are capital equipment that run best flat-out. Capacity utilization, throughput, and material yield (scrap rate) are the operating levers on the commodity side; a plant running two shifts at high utilization prints money, one running half-idle bleeds. Tooling life, changeover time, unplanned downtime, scrap, and heat-treatment or plating rejects can move contribution margins materially.
• Mix is the margin. Standard bolts and nuts are near-commodities — price-competitive, import-exposed, thin-margin. Engineered and specialty fasteners (aerospace, medical, exotic alloys, torque-to-yield automotive bolts) sell on specification and reliability, not price, and carry much fatter margins. Howmet's Fastening Systems segment — weighted toward proprietary aerospace products — reported 30.4% adjusted EBITDA margin in 2025, up from 25.8% in 2024, driven by aerospace growth and productivity.[22] At the opposite end, Chicago Rivet's Fastener segment generated $24.1 million of 2025 revenue while the consolidated company recorded a $1.1 million net loss.[19]
• Qualification is the moat. On the high end the durable advantage is not a patent — it's approvals. An aerospace fastener must be qualified to the exact aircraft program; switching suppliers means requalifying, which can take years. That lock-in is why aerospace fastener assets trade at high multiples[9] and why the segment is far more concentrated than the fragmented commodity base.
• Customer concentration matters. Chicago Rivet's largest customer represented approximately 19% of 2025 consolidated revenue, its second approximately 10%, and its third approximately 5%.[19] Aerospace suppliers face similar platform concentration and potentially severe consequences if an aircraft program is delayed.

Read a fastener business, therefore, on: capacity utilization, the steel-to-selling-price spread, product mix (percent specialty vs. commodity), qualification breadth, customer concentration, and — because demand is cyclical — order backlog into auto, construction, machinery, and aircraft.

6. What drives demand

Fastener demand is derived demand — it tracks the output of the things fasteners go into:

• Automotive (~30% of fastener demand). The single biggest end market; thousands of fasteners per vehicle across powertrain, chassis, body, and interior.[14] Vehicle build rates drive volume. Chicago Rivet generated $15.1 million of 2025 fastener revenue from automotive customers and $8.9 million from nonautomotive customers; management attributed weaker underlying automotive sales to lower North American vehicle production and inventory caution.[26]
• Construction (~27%). Structural bolts, anchors, and framing fasteners tied to residential and non-residential building activity.[14]
• Industrial machinery, heavy equipment, and robotics (~10–12% and the fastest-growing). Automation and reshored capital equipment lift precision-fastener demand.[14]
• Aerospace and defense. Small by tonnage, large by value and margin; driven by Boeing/Airbus build rates, engine production, and defense programs. Howmet's Fastening Systems sales increased 11% in 2025, which management attributed principally to commercial-aerospace growth.[22]

Structural shifts to watch: reshoring of U.S. manufacturing lifts domestic content; the electric-vehicle transition changes the mix (fewer engine fasteners, more battery-pack and lightweight-structure fasteners) more than the total — MacLean-Fogg explicitly links lightweight fasteners to fuel economy and battery range;[24] and factory automation raises demand for precision micro-fasteners. Lightweighting is a mix shift rather than a simple volume thesis: automakers and aerospace customers increasingly use aluminum, advanced high-strength steel, composites, and mixed-material assemblies, which can reduce some conventional steel-fastener content while increasing demand for engineered joining systems that prevent galvanic corrosion and reliably join dissimilar materials.

7. Regulation

This is a lightly product-regulated industry, but four regimes bite:

1. Fastener Quality Act of 1990 (Public Law 101-592). Passed after 1980s failures and counterfeit certification scandals, it requires that certain threaded metallic fasteners (nominal diameter ≥1/4 inch / 6 mm) that reference a consensus standard actually conform to it, with accredited testing and manufacturer grade-marking.[7][15] Compliance runs through recognized standards bodies — ASTM (American Society for Testing and Materials), SAE (Society of Automotive Engineers), ASME, and ISO.[7] Importantly, numerous categories — including many proprietary, aerospace-approved, and quality-system-produced fasteners — are exempt; the statutory scope is narrower than commonly assumed.
2. Trade remedies and tariffs. Fasteners are a chronic trade-case industry. A 25% Section 232 tariff on steel and aluminum and their derivatives now applies to many imported fasteners, and antidumping/countervailing duties have repeatedly targeted Chinese and Taiwanese product.[6] Trade policy is a first-order swing factor for domestic makers because imports supply most U.S. consumption (Section 3). Howmet specifically identifies tariffs, inflation, exchange rates, customer requirements, and its ability to recover tariff costs as uncertainties.[22]
3. Sector and quality rules. Aerospace suppliers must hold AS9100 quality certification and Nadcap process approvals.
4. Environmental rules. Plating and coating operations (zinc, electroplating, hexavalent chromium, cadmium) fall under EPA and OSHA rules. EPA's electroplating effluent guidelines limit discharges of cyanide and metals including lead, cadmium, copper, nickel, chromium, zinc, and silver for covered facilities; EPA is also examining PFAS discharges associated with certain chromium-finishing operations.[27] Chromium electroplating tanks are separately subject to hazardous-air-pollutant standards under 40 CFR Part 63, Subpart N.[28] For exported product, RoHS/REACH chemical restrictions apply.

8. Competitive dynamics and consolidation

The industry is two markets wearing one code:

• Commodity fasteners: fragmented and import-pressured. Hundreds of domestic shops (HHI ~160, CR4 18%[2]) compete on price against Taiwanese and Chinese imports that supply the majority of U.S. demand.[5] Consolidation here is a private-equity story: roll-ups such as MW Components (which bought Elgin Fastener Group in 2023[12]) and Optimas assemble regional shops to gain scale and cross-selling. Distribution has consolidated faster than manufacturing — Fastenal's vending/vendor-managed-inventory model and Grainger's scale reshape how fasteners reach customers.
• Aerospace and specialty fasteners: concentrated and defended. A handful of players — Howmet, Berkshire's Precision Castparts/SPS, LISI Aerospace, and PennAero (the former TriMas aerospace unit) — dominate, protected by program qualifications and exotic-alloy know-how.[9][10] High multiples on these assets (TriMas's ~18x EBITDA sale[9]) reflect that moat. Howmet's $1.8 billion acquisition of Consolidated Aerospace Manufacturing in April 2026 further consolidated the aerospace segment.[21]

9. Risks

• Steel input volatility. With metal at a huge share of cost,[25] a fast run-up in wire-rod prices squeezes margins before surcharges catch up. The economic sensitivity is not simply "steel up, margin down" — profitability depends on purchase-price timing, scrap recovery, customer price-adjustment formulas, the lag before repricing, alloy mix, and whether tariffs can be passed through.
• Import competition and trade whiplash. Most U.S. fastener consumption is imported;[5] tariff and antidumping regimes can swing a domestic maker's competitiveness overnight in either direction.[6] Tariffs can help a domestic producer against imported finished fasteners while simultaneously raising its imported rod, alloy, tooling, or finished-product costs.
• Cyclicality. Auto, construction, machinery, and aerospace all cycle; a downturn in any hits volume and utilization. Distributor inventory corrections can amplify the cycle because manufacturers experience both final-demand changes and customers' destocking.
• Concentration and single-point fragility. The February 2025 fire at SPS Technologies' plant reportedly knocked out roughly 15% of U.S. aerospace fastener supply, and post-pandemic aerospace fastener lead times ran 2–5x normal with 20–30% price inflation — a reminder that qualified capacity is thin and hard to replace.[13]
• Quality and liability risk. Quality and liability risks are disproportionate to the selling price of the part. A recall, false certification, or heat-treatment defect can create liabilities vastly exceeding the affected product revenue.
• EV and technology mix shift. The transition changes fastener content and specifications; makers tied to internal-combustion-specific parts must retool.
• Skilled-labor scarcity. The risk is less about total headcount than about experienced header operators, tool-and-die personnel, metallurgists, quality engineers, and maintenance technicians. Training is slow, and aggressive headcount reductions can impair yield or customer qualification.
• Substitution risk. Welding, adhesives, clinching, molded-in plastic features, and redesigns that eliminate separate hardware can substitute for mechanical fastening in some applications. Substitution is application-specific: removable joints and safety-critical assemblies often continue to require mechanical fastening, while commodity fasteners face greater design-out risk.
• Environmental liabilities. Legacy facilities may carry environmental liabilities attached to historical cleaning, heat-treatment, and finishing operations.

10. How to invest and the outlook

Public routes. Because no large U.S. pure-play exists, public investors choose an angle:

• Aerospace-fastener leverage: Howmet (HWM) is the most direct large-cap play on the tight, high-margin aerospace fastener cycle, with its Fastening Systems segment separately reported and expanded by the 2026 CAM acquisition;[21][22] Berkshire Hathaway owns Precision Castparts/SPS, though Berkshire does not disclose a separate fastener revenue figure.[23]
• Diversified-industrial exposure: ITW and Nucor embed fastener units inside bigger companies — you get the theme diluted by the parent.[8][11]
• Direct small-cap: Chicago Rivet & Machine (CVR) is the most direct listed exposure, though small ($24M fastener segment revenue), automotive-sensitive, and operationally volatile.[19]
• Pure-play (foreign-listed): LISI (Paris), Bossard and SFS (Zurich), Bufab and Bulten (Stockholm).
• Volume proxy via distribution: Fastenal (FAST) and W.W. Grainger (GWW) — not manufacturers, but clean, liquid bets on fastener throughput.[20]

Private routes. This is fundamentally a private-market industry. The opportunity set is family-owned regional manufacturers (succession-driven sellers), private-equity platforms and add-ons (the MW Components / Optimas model), and specialty/aerospace assets that command premium multiples on exit (the TriMas–PennAero deal at ~18x EBITDA is the template).[9][12] The most defensible targets generally possess proprietary parts, approved-supplier status, difficult metallurgy, strong traceability, diversified platforms, and a credible ability to pass through material costs. Commodity businesses require a lower entry multiple and greater attention to utilization, inventory quality, environmental history, and maintenance capital expenditure.

Near-term drivers (forward-looking). The setup favors specialty and domestic exposure over commodity. The commercial-aerospace production ramp against Boeing/Airbus backlogs is straining qualified fastener capacity, keeping specialty pricing firm; the 2025 SPS fire underlined how thin that capacity is.[13] Howmet's Fastening Systems sales increased 11% in 2025, driven principally by commercial-aerospace growth.[22] Tariffs and reshoring are, on balance, tailwinds for domestic manufacturers even as they raise input costs. Against that, the commodity end stays cyclical and import-pressured, hostage to auto and construction demand and to steel prices. The durable investment thesis in this industry is not "buy fasteners" broadly — it is to favor the qualification-protected, specialty, and aerospace niches where pricing power lives, and to treat the commodity base as a cyclical, trade-policy-driven trade.

Common analytical errors. The most common misreporting is to call Fastenal a major member of NAICS 332722 (it is a distributor), equate global "industrial fastener market" consumption with U.S. factory shipments, or apply aerospace-fastener margins to commodity plants. Establishments and firms are also frequently confused: Census establishment counts measure operating locations, not ultimate corporate owners.

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Sources

1. U.S. Census Bureau, County Business Patterns 2023, NAICS 332722 (establishments, employment, annual payroll). https://www.census.gov/programs-surveys/cbp.html
2. U.S. Census Bureau, 2022 Economic Census — Concentration by Largest Firms, NAICS 332722 (value of shipments, firm count, CR4/CR8/CR20/CR50, HHI), 2022. https://www.census.gov/programs-surveys/economic-census.html
3. U.S. Small Business Administration, Table of Small Business Size Standards (NAICS 332722 = 600 employees), 2023. https://www.sba.gov/document/support-table-size-standards
4. Roche Industry, "The 10 Best Fastener Manufacturers in the USA," 2026 (U.S. fastener market ~$23.6B in 2024, >$29B by 2030). https://www.rocheindustry.com/fastener-manufacturers-in-the-usa/
5. Fastener World, "Facing U.S. 25% Tariff, Taiwanese Suppliers…" (U.S. fastener import shares: Taiwan, China, Japan), 2025. https://www.fastener-world.com/en/article/9104.html
6. ArkFastech, "Recent U.S. Tariff Policies and Their Impact on Taiwanese Fastener Products" (25% Section 232 steel/aluminum derivative tariff on fasteners), 2025. https://www.arkfastech.com/th/knowledge-detail/Carbonitriding__1/
7. NIST, "Compliance FAQs: Fastener Quality Act (FQA)"; U.S. Bureau of Industry and Security, "Fastener Quality Act," 2022. https://www.nist.gov/standardsgov/compliance-faqs-fastener-quality-act-fqa
8. Illinois Tool Works Inc., Form 10-K, FY2024/2025 — Construction Products segment (Paslode, Ramset, Red Head). https://s204.q4cdn.com/218186261/files/doc_financials/2025/sr/10-K.pdf
9. TriMas Corporation, "TriMas Completes the Divestiture of TriMas Aerospace" (sale to PennAero/Tinicum, ~$1.45B, ~18x EBITDA, closed March 16, 2026), 2026. https://trimas.com/news/2026/trimas-completes-the-divestiture-of-trimas-aerospace/
10. Howmet Aerospace Inc., Form 10-K, FY2024 — Fastening Systems segment, 2025. https://www.sec.gov/Archives/edgar/data/4281/000000428125000011/hwm-20241231.htm
11. Nucor Corporation, "Nucor Fastener to Expand with Acquisition of Coil Processing Facility" (St. Joe, IN; ~75,000 tons/yr; large-diameter capacity), 2021. https://nucor.com/news-release/nucor-fastener-to-expand-with-acquisition-of-coil-processing-facility-122560
12. Global Fastener News / PR Newswire, "MW Components Acquires Elgin Fastener Group" (September 2023). https://www.prnewswire.com/news-releases/mw-components-expands-fastener-products-through-acquisition-of-elgin-fastener-group-301923441.html
13. Melfast, "How the 2025 Aerospace Fastener Shortage Affects Your Supply Chain" (SPS Technologies fire ~15% of U.S. aerospace fastener supply; lead-time and price impacts); U.S. GAO, Commercial Aviation Manufacturing: Supply Chain Challenges, GAO-24-106493, 2024. https://www.melfast.com/blog/how-the-2025-aerospace-fastener-shortage-affects-your-supply-chain
14. GMInsights, "Industrial Fasteners Market Size, 2025–2034" (end-market shares: automotive ~30%, construction ~27%, machinery/robotics fastest-growing). https://www.gminsights.com/industry-analysis/industrial-fasteners-market
15. U.S. Congress, Public Law 101-592 — Fastener Quality Act, November 16, 1990. https://www.congress.gov/101/statute/STATUTE-104/STATUTE-104-Pg2943.pdf
16. NAICS Association / U.S. Census Bureau, "NAICS Code 332722 — Bolt, Nut, Screw, Rivet, and Washer Manufacturing" (definition; exclusion of precision turned products, NAICS 332721), 2022. https://www.naics.com/naics-code-description/?code=332722
17. National Fastener Distributors Association / Fastener Training Institute, production methods overview (cold and hot heading, screw machining, thread rolling, grinding, heat treatment, plating). https://www.nfda-fastener.org/index.php?category=industry+news&id=329%3Afastener-training-institute-to-present-two-training-classes-at-fastener-fair-usa&option=com_dailyplanetblog&view=entry
18. Industrial Fasteners Institute, IFI Membership Brochure (160+ member companies across U.S., Canada, Mexico). https://media.indfast.org/wp-content/uploads/2022/08/2021-IFI-Membership-Brochure.pdf
19. Chicago Rivet & Machine Co., Form 10-K, FY2025 (fastener segment revenue, net loss, customer concentration, competitive landscape). https://www.sec.gov/Archives/edgar/data/19871/000001987126000004/cvr-20251231.htm
20. Fastenal Co., Form 10-K, FY2025 (supply chain economics, supplier geography, customer mix, fastener share of sales). https://www.sec.gov/Archives/edgar/data/815556/000081555626000009/fast-20251231.htm
21. Howmet Aerospace Inc., Form 8-K, April 6, 2026 (completion of Consolidated Aerospace Manufacturing acquisition from Stanley Black & Decker for ~$1.8B). https://www.sec.gov/Archives/edgar/data/4281/000110465926039791/tm2611168d1_8k.htm
22. Howmet Aerospace Inc., Form 10-K, FY2025 (Fastening Systems segment: $1.745B revenue, 30.4% adjusted EBITDA margin, 11% sales growth, input costs, tariff risks). https://www.sec.gov/Archives/edgar/data/4281/000000428126000012/hwm-20251231.htm
23. Berkshire Hathaway Inc., Form 10-K, FY2025 (Precision Castparts/SPS Technologies and Marmon ownership; no separate fastener disclosure). https://www.sec.gov/Archives/edgar/data/1067983/000119312526083899/brka-20251231.htm
24. MacLean-Fogg Company, news release (automotive, heavy truck, industrial fastener applications; lightweight fasteners for fuel economy and battery range). https://macleanfogg.com/news/mfcs-ribe-announce-joint-venture/
25. IMARC Group / SteelOnTheNet, "Steel Wire Rod Manufacturing" and "Long Steel Products" (cold-heading-quality rod as input; raw material share of cost), 2026. https://www.steelonthenet.com/essentials/long-steel-products.html
26. Chicago Rivet & Machine Co., 2025 Annual Report (automotive vs. nonautomotive fastener revenue breakdown). https://www.chicagorivet.com/wp-content/uploads/AnnualReport-2025.pdf
27. U.S. Environmental Protection Agency, "Electroplating Effluent Guidelines" (discharge limits for cyanide, lead, cadmium, copper, nickel, chromium, zinc, silver; PFAS examination). https://www.epa.gov/eg/electroplating-effluent-guidelines
28. U.S. Environmental Protection Agency, "Chromium Electroplating: National Emission Standards for Hazardous Air Pollutants" (40 CFR Part 63, Subpart N). https://www.epa.gov/stationary-sources-air-pollution/chromium-electroplating-national-emission-standards-hazardous-air