Guides / Materials
5-Axis CNC Machining Aluminum Parts: Which Grade and What It Costs
September 20, 2026
Aluminum is the material most 5-axis shops cut every day. It machines fast, holds a good tolerance and takes finishing well, which is why it is the default choice unless the part has a specific reason to be something else.
Why aluminum is the default 5-axis material
Aluminum removes material quickly compared to steel or titanium, which keeps machine time and cost down. It also generates less heat at the cutting edge, so tools last longer between changes. For a shop quoting a new part, aluminum is usually the lowest-risk material to price accurately, which is part of why it dominates prototype and low volume work.
Choosing a grade
| Grade | Typical use | Notes |
|---|---|---|
| 6061-T6 | General structural parts, brackets, housings | Good machinability, weldable, widely stocked |
| 7075-T6 | High strength to weight parts, aerospace brackets | Stronger than 6061, not weldable, costs more |
| 2024-T3 | Fatigue-critical structural parts | Common in aerospace skins and structure, less common as billet stock |
| Cast aluminum (A356 etc.) | Parts with a cast starting blank machined to finish | Used when the geometry favors casting plus finish machining |
For most parts sourced through a 5-axis matching service, the choice comes down to 6061 versus 7075. If the drawing does not call out a specific alloy for a structural or certification reason, 6061 is worth asking about first since it is the more widely available and usually less expensive option.
Tolerance and surface finish you can expect
5-axis aluminum parts commonly hold ±0.01 to ±0.025 mm on critical features, tighter than most plastics and comparable to stainless steel. As-machined surface finish typically lands around Ra 1.6 to 3.2 micrometers, smooth enough for most functional surfaces without a secondary finishing step.
Common 5-axis aluminum parts
- Housings and enclosures with features on multiple faces
- Brackets and mounts with angled bores
- Manifolds and fluid handling parts
- Robotics and automation structural components
- Optical and sensor mounts
- Prototype and low volume aerospace structure
Finishing options
Anodizing is the most common finish for aluminum parts, both for corrosion resistance and for a controlled cosmetic appearance. Type II anodizing is the standard option; Type III (hardcoat) adds wear resistance for moving or sliding surfaces. Alodine (chromate conversion coating) is used when electrical conductivity needs to be preserved. Bead blasting before anodizing gives a uniform matte texture. All of these are typically done by an outside finishing specialist after machining, which adds a few days to the lead time.
Cost compared to stainless and titanium
Aluminum is almost always the least expensive of the three to machine. Stainless steel cuts more slowly and wears tools faster, adding machine time even when the geometry is identical. Titanium adds both slower cutting and a material cost per kilogram that is several times higher than aluminum. If a design allows a choice between materials, ask the shop for the price difference. It is often larger than expected and can change which material makes sense for the application.
What to put on your RFQ
Specify the exact alloy and temper (6061-T6, not just “aluminum”), the tolerance on features that mate with other parts, and any finish requirement including color if anodizing. If you are open to either 6061 or 7075 depending on price, say so. Letting the shop quote both gives you a real comparison instead of a single number.
The short version
6061 covers most general aluminum parts at the lowest cost, 7075 earns its price on strength-critical applications. Both hold a good tolerance and finish well on a 5-axis machine, and both cost less to cut than stainless or titanium, which is why aluminum is the starting point for most new part quotes.
See also: Aluminum Alloys on 5-Axis Machines: 6061, 7075, 2024 and Cast Plate.
Frequently asked questions
Which aluminum grade is best for 5-axis machining?
6061 for most structural and general parts, 7075 when higher strength to weight matters. Both machine well on 5-axis equipment and are widely stocked.
Is aluminum cheaper to machine than steel?
Usually yes. Aluminum cuts faster and wears tools more slowly, which lowers machine time even before material cost is counted.
Can 5-axis aluminum parts be anodized?
Yes. Type II and Type III anodizing are common finishes, usually done by an outside specialist after machining.
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