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Wrought Copper Alloy Bar & Plate (UNS "C" 100 through 700 series of WROUGHT copper alloy numbers) are produced to size within a plus and minus tolerance per the ASTM standards. For example if you order a 1" solid dia. C36000 brass rod the OD tolerance will be +/-.002". If you are finishing to 1.000" OD or less, you will need to order the next OD size up for example 1.125" OD. For rolled (wrought) plate , for example,  1/2" thickness tolerance would be +/-.028". If you are finishing to 0.500" thickness or less you would need to order the next standard thickness up which for example may be 0.625" thick.

Cast Copper Alloy Bar & Plate (UNS "C" 800 & 900 series of CAST copper alloy numbers) are produced to "Nominal" sizes. This means finishing allowance already remains to finish to the published size. For example, if you order a CAST C95400 aluminum bronze 3" solid dia. bar the actual cast size will be 3.063" (+/-.010") and will finish to 3.000" diameter or less. If you need a tin-leaded bronze tube in a cast alloy, for example, 2" ID x 3" OD the AS CAST ID will be 2" (-.031") ID x 3" (+.031") OD and will finish to 2.000" ID x 3.000" OD.

TOLERANCES & FINISHING ALLOWANCES

Cast Bronze Finishing Allowances

 Hollow Tube (Round Only)

Tin Bronzes and Leaded Tin Bronzes

Cast Bronze Finishing Allowances

Solid Round Bar, Rectangle, Hexagons

 Tin Bronzes and Leaded Tin Bronzes

Cast Bronze Finishing Allowances

 Hollow Tube (Round Only)

Aluminum Bronzes and Manganese Bronzes

Cast Bronze Finishing Allowances

Solid Round Bar, Rectangles, Hexagons

Aluminum Bronze & Manganese Bronzes

Cast Bronze Diameter Tolerances

Solid Round Bar, Tube, Squares, Rectangles, Hexagons

Tin Bronzes and Leaded Tin Bronzes

Cast Bronze Diameter Tolerances

Solid Round Bar, Tube, Squares, Rectangles, Hexagons

Aluminum Bronzes & Manganese Bronzes

UNDERSTANDING CAST TOLERANCES & FINISHING ALLOWANCES WILL SAVE YOU TIME & MONEY

For Example, a buyer asks a supplier for C93200 (SAE 660) Bronze Tube and the buyer is finishing to 8.000" OD. A Buyer unaware of NOMINAL specifications, may ask for 8.250" OD adding the clean up allowance themselves. Since 8.250" OD is non-standard the buyer will be offered NOMINAL 8.500" (+ .125") OD or NOMINAL 9.000" (+ .125") OD WHEN THE NOMINAL 8" (+ .125") OD WOULD HAVE FINISHED TO 8.000" OD OR LESS. If buyers are unaware of the NOMINAL Finishing Allowances per the ASTM specifications they can waste many thousands of dollars over time by purchasing sizes with unnecessary extra finishing allowance.

THE DIFFERENCE BETWEEN FINISHING ALLOWANCES AND TOLERANCES

For example, 3" ID x 4" OD C95400 CAST Aluminum Bronze Tube. Referring to the Finishing Allowance Charts you will see that the Finishing Allowance is 3" (-.125") ID x 4" (+.094") OD. Therefore the cast AIM size is 2.875" ID x 4.094" OD. However, as with anything, there is a tolerance to these dimensions. The tolerances for this example, will be 2.875" (+.015" / - .050") ID x 4.094" (+/-.015") OD. The ACTUAL tube size can be 2.890"/2.860" ID x 4.079"/4.109" OD. In Cast Alloys this is what is called a NOMINAL 3" ID x 4" OD Tube and will finish to 3.000" ID x 4.000" OD.

Let us look at a Rectangle. NOMINAL 1" x 4" C86300 cast Manganese Bronze Rectangle will be 1" (+ .094") THICK x 4" (+ .094") WIDE. Therefore the CAST AIM is 1.094" THICK x 4.094" WIDE. Referring to the Tolerance Chart the actual cast size can be 1.094" (+/ .020") x 4.094" (+/- .040"). The Rectangle size can be 1.074"/ 1.114" THICK x 4.074"/4.114" WIDE. In Cast Alloys this is what is called a NOMINAL 1" THICK x 4" WIDE Rectangle and will finish to 1.000" Thick x 4.000" wide.

bronze plate tolerances

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What's Driving
Metal Prices

Factors creating the on-going surge in copper prices and base metal prices.

The U.S. imposed a 50% Section 232 tariff on the copper content of semi-finished and derivative copper products, effective August 1, 2025. These tariffs aim to bolster domestic production but create complexities for businesses in pricing, sourcing, and compliance, affecting global copper markets. 

In addition copper costs are soaring due to massive demand from the energy transition (EVs, renewables, grid) and AI data centers colliding with slow mine supply growth, production disruptions (labor, technical issues), aging mines, and government policies like tariffs, creating a structural supply deficit. 

Tin prices jumped to a record level due to a severe, ongoing global supply squeeze from mine disruptions (DRC, Myanmar, Indonesia) and increasing demand driven by its critical role in electronics (solder), green energy tech, and packaging, creating a significant market deficit and attracting speculative investment. Supply chain issues, including export permit delays and political instability in key producing regions, combined with growing recognition of tin's necessity for the energy transition, fueled a rally to multi-year highs in late 2025 and early 2026. 

Nickel prices are rising due to anticipated supply cuts from major producer Indonesia, tighter quotas, increased demand from stainless steel and EV battery sectors (despite some LFP shifts), speculative buying, and broader market strength in metals, with investors reacting to policy signals and potential disruptions.

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