New U.S. Metal Tariff Rules Are Raising Costs on CNC Parts — Effective April 6

By PartsPrecision.com | April 14, 2026

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What Changed on April 6
The New Rate Structure at a Glance
Why This Hits CNC Parts Buyers Directly
What the Rules Say About Derivative Products
Exceptions Worth Knowing
What Buyers Should Do Now
Sources

What Changed on April 6

On April 2, 2026, President Trump signed a proclamation fundamentally restructuring the Section 232 tariff regime for steel, aluminum, and copper imports. The changes took effect at 12:01 a.m. on April 6, 2026.

The core shift is this: tariffs now apply to the full customs value of imported metal goods and their derivative products — not merely the value of the metal content embedded in them. Under the prior system, which had been in place since June 2025, importers of mixed metal-and-non-metal products calculated duties only on the declared metal component, separating it from labor, machining, and manufacturing costs. That methodology has been eliminated.

For buyers sourcing precision-machined parts made of steel, aluminum, or copper from outside the United States, this change is not administrative. It directly raises the duty base on which tariffs are calculated, and in many cases significantly increases the landed cost of imported components.

The New Rate Structure at a Glance

The proclamation divides covered products into tiers based on metal intensity:

50% tariff — Articles made entirely or almost entirely of steel, aluminum, or copper. This includes steel coils, aluminum sheet, bar, plate, castings, forgings, copper bar and plate, and certain high-intensity derivatives. These are assessed on their full customs value.

25% tariff — Derivative articles substantially made of steel, aluminum, or copper. This covers many machined components, fabricated metal parts, and machinery articles listed under HTSUS Chapters 84 and 85 that were added to Section 232 scope in mid-2025.

15% transitional tariff — Metal-intensive industrial equipment and electrical grid equipment, effective through December 31, 2027, to support domestic industrial buildout.

10% tariff — Derivative articles made abroad entirely using U.S.-smelted, -cast, or -poured aluminum, steel, or copper. This provides a meaningful incentive for manufacturers that source American-origin metal inputs even when producing overseas.

Exempt — Products containing 15% or less of the aggregate weight of applicable metals are no longer subject to Section 232 tariffs. This removes hundreds of lightly metal-containing products from the scope entirely.

Why This Hits CNC Parts Buyers Directly

Before April 6, an importer of a machined aluminum housing could separate the value of the aluminum from the value of the machining and apply the tariff only to the metal portion. A housing with $40 in aluminum content and $160 in machining value, for example, would generate a tariff on $40 at 50% — a $20 duty. Under the new system, the 25% tariff applies to the full $200 customs value — a $50 duty. That is a 150% increase in the actual duty paid, on the same part.

This structural change applies broadly to precision-machined components made of steel, aluminum, and copper imported from non-trade-agreement countries. For companies that have been sourcing CNC-machined parts from China, Taiwan, or other countries without preferential trade agreements with the U.S., the impact is immediate and material.

The proclamation does not provide any exception for goods already in transit at the time it took effect. Shipments that entered consumption on or after April 6 are subject to the new rates regardless of when they were ordered or shipped.

What the Rules Say About Derivative Products

The category of “derivative articles” is where the greatest complexity — and exposure — sits for precision parts buyers.

Under the new framework, derivative articles listed in Annex I-B (which includes many machined parts and machinery components under HTSUS Chapters 84 and 85) are subject to the 25% full-value tariff. This covers a wide range of fabricated metal components that were previously either exempt or taxed at a lower effective rate under the metal-content calculation method.

Critically, the proclamation terminates the prior quarterly “derivatives inclusion process” — the mechanism by which new products were formally added to Section 232 scope through Federal Register notices and public comment periods. Going forward, the U.S. Department of Commerce and the Office of the U.S. Trade Representative can jointly add derivative articles without the prior public process. This means the scope of covered products can expand with less advance warning.

No stacking: The proclamation clarifies that for products containing more than one covered metal, importers pay only a single Section 232 duty — the highest applicable rate — rather than layered duties for each metal present.

Exceptions Worth Knowing

Several specific exceptions are written into the proclamation and its annexes.

U.S.-origin metal reduction. Parts imported from any country but made entirely with U.S.-smelted or U.S.-cast aluminum, steel, or copper qualify for the 10% rate. For manufacturers able to source and document U.S.-origin metal inputs, this is a significant cost lever.

United Kingdom reduced rates. Under ongoing bilateral trade discussions, UK products continue to receive reduced treatment: 25% (instead of 50%) for Annex I-A goods, and 15% (instead of 25%) for Annex I-B goods, provided the metal content meets UK-origin criteria.

Civil aircraft parts. Reciprocal trade agreements with the UK, EU, Japan, and South Korea include exceptions for civil aircraft and parts from Section 232 tariffs. These exceptions are maintained in the proclamation.

De minimis on metal content. Products not classified in HTSUS Chapters 72 (iron and steel), 73 (articles of iron or steel), 74 (copper), or 76 (aluminum) that contain less than 15% of the aggregate weight of covered metals are exempt entirely.

Prototype exemption. As restored in July 2025, prototypes continue to be exempt from Section 232 tariffs — relevant for engineering teams sourcing sample quantities for design validation.

What Buyers Should Do Now

Reclassify your imports immediately. The move to full-value tariff calculation changes the duty exposure for many products that were previously partially or lightly affected. Review your imported component classifications against the new Annexes — the change in effective duty rate may be substantial.

Audit your supply chain for U.S.-origin metal pathways. If any of your overseas suppliers use U.S.-origin aluminum, steel, or copper, the 10% reduced rate may apply. This requires supplier-level documentation of metal origins, but the cost savings justify the effort.

Recalculate total landed cost on all metal parts. The prior landed cost model — which separated metal value from machining value for tariff purposes — no longer holds. Every metal part imported from a non-treaty country needs a fresh total cost analysis.

Explore the U.S.-origin metal reduction. If your supplier can document that parts are manufactured using U.S.-smelted or U.S.-cast metal — even when produced overseas — the applicable Section 232 rate drops to 10%. This exception is significant and underused. Work with your suppliers to verify whether this pathway applies to your components.

Consult customs counsel on complex classifications. The new Annexes are detailed and cover hundreds of specific HTSUS subheadings. For high-volume imports, professional classification review is worth the investment to avoid under- or over-payment of duties.

At PartsPrecision.com, we are a precision CNC parts manufacturer helping customers navigate these tariff changes with transparent pricing and full documentation. Contact our team to discuss your sourcing requirements and how we can support your supply chain.

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