CNC Aluminum Parts From Orange County

• 1
  What makes aluminum fast to cut and easy to distort
• 2
  Which aluminum alloy fits which part
• 3
  How setup count drives tolerance and cost
• 4
  Surface finish, anodizing and what inspection catches
• 5
  Matching aluminum grade and process to the part

Aluminum cuts at high surface speed. On a 6061-T6 part, a 12 mm carbide end mill can run 8,000–12,000 rpm and still take a 3–5 mm radial cut, so a simple bracket can go from stock to finished part in a single shift. That speed is not a marketing claim. It comes from low cutting force and good heat transfer into the chip.

The same properties that make aluminum easy to cut make it easy to distort. It has roughly one third the elastic modulus of steel, so a thin rib pushes away from the cutter instead of shearing cleanly. The tool deflects the wall, the wall springs back, and the finished dimension lands outside the tolerance band.

This is where the sourcing question actually starts. A shop can hold ±0.005 mm on a 20 mm thick housing and miss it on a 1.5 mm fin from the same bar. Geometry decides the process. Alloy decides how much the geometry fights you.

Heat is the second limit. Aluminum conducts heat away from the cut quickly, which protects the tool, but the part grows as it warms. A 200 mm long plate can move 0.05–0.1 mm between a cold first cut and a warm last cut. Rough, cool, then finish. That sequence costs one extra setup and saves a scrapped part.

6061-T6 is the default for a reason. It welds, anodizes cleanly, machines at high feed and holds ±0.005 mm on stable geometry. If a part has no extreme strength or temperature demand, start here and stop looking.

7075-T6 buys strength and pays for it. Yield strength is roughly double that of 6061, which matters for aircraft fittings and high-load brackets. It also chips harder, cuts slower, and shows tool marks more readily, so the same surface finish may need an extra finishing pass.

2024-T3 is a fatigue alloy. It suits parts that see cyclic loading, such as actuator links and wing components. It has lower corrosion resistance than 6061, so it usually gets a protective finish rather than being left bare.

5052 and 5083 are the forming and marine grades. They bend well and resist salt water, but they are gummy on the mill and rarely hold tight tolerances. Use them for covers, panels and enclosures where the bend radius matters more than the tenth.

ADC12 is a die casting alloy, not a billet grade. When a housing will be cast and then only touched up on critical faces, that is a different process plan from machining the whole shape from plate.

Every time a part is unclamped and turned, the datum moves. A 3-axis machine needs one setup per face. A part with features on five sides needs five setups, five fixture positions, and five chances to stack error.

Five-axis machining removes most of that. The tool reaches the part from any angle while the part stays clamped, so a complex housing with deep pockets and undercuts comes off in one or two setups. On turbine-blade profiles and aerospace brackets, that single change often decides whether the tolerance is reachable at all.

Our 16 simultaneous 5-axis machining centers carry a Ø400 mm rotary table and handle parts up to 4,000 mm on the long travel. That range covers most Orange County work, from a hand-sized medical manifold to a long structural beam.

Setup reduction also cuts cost, but not in a straight line. Programming a 5-axis toolpath takes longer than a 3-axis one, and a short run of three parts may not repay that time. Above roughly twenty parts, the math flips toward 5-axis.

As-machined aluminum sits around Ra 1.6–3.2 μm. A normal finishing pass reaches Ra 0.8–1.6 μm, which is the working range for most mating faces and O-ring grooves. Ra 0.2–0.8 μm needs a deliberate step: lighter depth of cut, higher spindle speed, sharp tooling.

Finish choice interacts with alloy. 6061 anodizes evenly in clear, color and hardcoat. 7075 takes hardcoat well but can show a color shift between batches. 2024 usually wants a conversion coating rather than cosmetic anodizing.

Bead blasting hides tool marks and gives a uniform matte look, but it also rounds sharp edges slightly. If a part has a sealing face or a press fit, mask it before blasting.

Inspection is where the tolerance claim becomes real. We check raw material, monitor in-process, and inspect 100% before shipment, with reports on request. On a thin-wall part, the final inspection happens after the part has cooled and relaxed, not straight off the machine.