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Metal surface finishing is not one process—it is a ladder of grit sizes, each producing a different roughness. A mill finish plate ships as-rolled and scaly. A No.4 brushed plate hides scratches. A mirror 8K plate reflects like chrome. Pick the finish that matches your application, because each step up costs money and time.

Step 1: Start with Mill Finish

All plate arrives as-rolled from the mill. Copper plate in mill finish has visible rolling lines and oxide. Mold steel in mill finish has a black forged scale. At this stage, Ra runs 1.5–3.5 μm. This is fine for structural parts that will be painted, machined, or hidden inside equipment. However, it is not acceptable for visible surfaces or food-contact parts.

Step 2: Grind to a Uniform Flat Surface

Next, the plate passes through a belt grinder with 80–120 grit abrasive. This removes mill scale and rolling lines. The result is a uniform, matte surface at Ra 0.8–1.5 μm. For copper busbars and industrial equipment panels, this brushed finish is the default. Furthermore, it hides minor scratches that occur during installation.

Step 3: Polish to No.4 Brush Finish

For decorative or visible surfaces, finer belts (180–240 grit) produce a No.4 brushed finish. Ra drops to 0.4–0.8 μm. This finish appears on architectural copper panels, appliance fronts, and kitchen equipment. It looks clean, yet it still hides handling marks.、

Step 4: Polish to Mirror (8K) Finish

Mirror finish requires multiple steps: 320 grit → 400 grit → 600 grit → buffing compound. At the end, Ra reaches 0.05–0.1 μm, and the plate reflects like a mirror. This finish suits decorative trim, optical reflectors, and mold cavities where plastic flow matters. However, mirror finish scratches easily; consequently, it needs protective film during transport and installation.

Roughness Numbers Buyers Actually Specify

Finish	Roughness Ra	Appearance	Cost multiplier
Mill	1.5–3.5 μm	As-rolled, scaly	1×
Ground	0.8–1.5 μm	Matte, uniform	1.3×
No.4 brushed	0.4–0.8 μm	Satin, directional	1.6×
600 grit polish	0.2–0.4 μm	Semi-bright	2×
8K mirror	0.05–0.1 μm	Reflective	3–5×

What We Supply in Finished Condition

We ship plate in several surface conditions:

• C11000 / T2 Copper Plate in mill finish, brushed, or polished for electrical busbars and decorative applications.
• H13 / SKD61 Mold Steel pre-machined and soft-annealed, ready for the mold maker’s own polishing.
• D2 / SKD11 Mold Steel in pre-hardened condition for tool rooms that finish-polish cavities.

Specify the Finish in Your PO

A complete order reads: “C11000 copper plate, 10 mm × 1000 × 2000 mm, No.4 brushed finish, PVC film both sides.” Leave out the finish and you receive mill finish, which costs you grinding time in your own shop.

Get the Right Surface Finish

Tell us your application and required roughness. We will confirm available finish options and quote with a mill certificate.

• Email: vera.liang@ztwysteel.com
• Location: Xishan District, Wuxi, Jiangsu, China
• Supply range: copper & brass plate, mold steel, nickel alloys, electrical steel, wear plate
• Documentation: MTC with chemistry, dimensions, and surface finish
• Services: grinding, brushing, polishing, PVC film protection

We reply within one working day.