Aluminum Parts CNC Milling Machining Service

Aluminum is the default metal for milled prototypes and mid-volume production because it cuts fast, holds a good finish, and weighs about a third of steel. The catch is that the alloy decides how the tool behaves. We stock 6061, 6061-T6, 2024, 5052, 5083, 6063, 6082, 7075, and ADC12. That list is not interchangeable.

6061-T6 is the workhorse. It machines cleanly, welds, anodizes well, and gives a good strength-to-weight ratio for brackets, housings, and fixture plates. 7075 is roughly twice the yield strength of 6061 and is what we reach for on aircraft fittings and high-load structural parts. It also chips differently, so feeds and speeds are set lower to avoid chatter.

2024 machines to a very fine finish and is common in aerospace skins and bushings, but it has poor corrosion resistance unless it gets a protective coating. 5052 and 5083 are marine-grade and gummy to cut; they are better formed than milled, and we say so when a drawing comes in as a thin bent panel in 5052.

ADC12 is a die-casting alloy. It can be milled for trim operations or post-cast features, but milling a full part from ADC12 billet is rarely the cheapest route. If your part is a high-volume housing, die casting plus finish milling usually beats cutting it from plate.

• 1
  6061-T6General machining, good finish, anodizes well. Default choice.
• 2
  7075-T6High strength, aerospace and load-bearing parts. Harder on tools.
• 3
  2024Fine finish, fatigue resistant, needs coating for corrosion.
• 4
  5052 / 5083Corrosion resistant, gummy. Better for formed sheet than milling.

A common mistake is quoting a 5-axis job that fits on a 3-axis machine. Axis count should follow the feature geometry, not the other way around. A flat plate with drilled holes and a pocket is a 3-axis part. Add features on the side faces and you either need a second setup or a 4-axis tombstone.

We run 27 three-axis machines, 12 four-axis mills, 16 mill-turn centers, and 16 simultaneous 5-axis machining centers. The 5-axis centers earn their rate when a part has compound angles, contoured surfaces, or undercuts that would otherwise need three or four refixtures. Every refixture is a chance to lose position, so on tight work 5-axis often holds tolerance better even when the cycle is longer.

Work envelope matters too. Our largest travel is 4,000 × 400 × 150 mm, with 750 × 1,150 × 550 mm, 600 × 600 × 600 mm, 500 × 500 × 450 mm, and 500 × 310 × 200 mm beds in the mid and compact range. There is a Ø400 mm rotary table for round and index work. If your part is long and thin, the 4,000 mm machine is the one to ask about, but flatness over that length depends on stock and fixturing, not just travels.

Thin walls are the other constraint. Below about 1 mm wall on aluminum, tool pressure starts to deflect the part and you hear it. Light radial cuts, high spindle speed, and sometimes a sacrificial support rib get you through. If a wall is 0.5 mm over a long span, we will flag it before cutting rather than after.

Our standard achievable tolerance is ±0.005 mm (±0.0002 in) on critical features. That number is real on the right part: a rigid 6061 bracket with a reamed bore, machined in one setup, measured on a warm part. It is not realistic on a 300 mm long, 2 mm thick plate, because thermal expansion of aluminum is about 23 μm per meter per degree Celsius. A 5 °C shop swing moves the part more than the tolerance.

So we ask which features carry the tight callout. Usually three or four dimensions matter and the rest can sit at ±0.1 mm. Marking those on the drawing lets us plan setup, choose the machine, and decide where to leave stock for a finish pass. Tightening everything raises cost without improving function.

Surface finish is tied to the same logic. Ra 1.6–3.2 μm is a normal as-machined aluminum surface. Ra 0.8–1.6 μm comes from finer stepovers and a sharp tool, and Ra 0.2–0.8 μm needs a dedicated finishing pass, often on a part that is already stable. Asking for Ra 0.4 μm on a part that will be bead blasted afterward is money spent twice.

Every part gets raw material verification, in-process checks, and a final inspection before shipment. That inspection runs 100% on our production, and dimensional reports are available on request. If you need first article inspection with a full ballooned drawing, say so in the RFQ so the quote includes it.

Anodizing adds a coating that grows into and onto the surface. Type II clear typically adds 5–15 μm per side on aluminum, and hardcoat can add more. On a bore with a ±0.01 mm tolerance, that growth is enough to matter. We mask critical diameters or pre-machine them undersize so the finished part lands in spec.

We offer clear, color, hardcoat, and conductive anodizing, plus electroless nickel, zinc, silver, and gold plating, powder coating, black oxide, bead blasting, tumbling, brushing, and polishing. Laser marking and engraving are available with a minimum character height of 1.5 mm, so a 0.8 mm part number will not read cleanly.

Threads are worth a note. Cut threads in aluminum are standard, but in thin plates under about 3 mm a formed thread or a pressed insert holds better. For parts that get assembled and disassembled repeatedly, specify a helicoil or a threaded insert and give us the insert callout; we will machine the pilot to match.

Deburring is included on edges we machine. If your drawing calls a sharp edge, mark it. Otherwise we break edges by default, because a 0.1 mm burr on a mating face will throw off an assembly.

Milling removes material, so it is fastest and cheapest when the part is not mostly air. A large, thin, flat enclosure panel is a sheet metal part, not a milled part, and quoting it as milling wastes your budget. We run sheet metal fabrication and will route it there if that is the honest answer.

Very high volumes change the math too. Past roughly 10,000 identical small parts a year, die casting or extrusion plus finish machining often beats cutting from billet. The tooling cost pays back on cycle time and material waste.

Parts with internal cavities that no cutter can reach are another limit. A straight end mill needs line-of-sight access. If a channel turns a corner inside the part, milling cannot produce it in one piece. Options are splitting the part and joining it, or switching to 3D printing or vacuum casting for the prototype stage.

Finally, if the part is a prototype for a process that will ultimately be molded or cast, do not over-engineer the milled version. Machine the features that will exist in the final part, and leave the rest simple.

Send a STEP or IGES file plus a 2D drawing if you have one. The 3D file tells us geometry; the 2D drawing tells us tolerances, finish, and threads. If there is no drawing, we machine to a general tolerance and note that in the quote.

Include the alloy if it is fixed, the quantity, and the finish. If the alloy is open, tell us the function and we will suggest one. We return a quotation and a free DFM analysis within 12 hours, and production can start within 24 hours of approval. Typical parts ship in 3–5 days.

We work from one prototype to 10,000+ part runs with no minimum order quantity. Uploads are handled as confidential, and an NDA is available on request if your program needs one. GreatLight has been machining since 2011, with 150 technicians across 7,600 m² in three wholly-owned plants. Certifications are ISO 9001:2015, IATF 16949:2016, ISO 13485:2016, and ISO 27001:2022.