CNC Machining Quote Guide for Aluminum Parts

You upload a STEP file and get a cnc machining quote back in seconds. That number only means something if your aluminum part is designed the way it will actually be cut. Alloy grade, wall thickness, tolerance and finish all move the price — sometimes by 30% or more between two parts that look identical on screen.

This guide walks through what to check before you request a price for an aluminum part: which alloy to specify, how tight to hold tolerances, what wall thickness a 3-axis or 5-axis mill can actually hold, and which finish is worth the extra lead time.

Choosing the Right Aluminum Alloy for Your CNC Machining Quote

Aluminum is the default choice for prototypes and production runs because it machines fast, holds tolerance well and costs less than steel per hour of spindle time. Not all aluminum is equal, though — the alloy you specify changes both the price and the performance of the finished part. For most aluminum CNC machining jobs, 6061-T6 covers the majority of parts we quote, so check the material dropdown before you assume anything else is loaded by default.

6061-T6 vs 7075-T6

6061-T6 is the workhorse: good machinability, weldable, anodizes cleanly and runs about 30-40% cheaper than 7075-T6 per kilogram. 7075-T6 is stronger — roughly double the tensile strength — but it work-hardens faster, wears tooling quicker and costs more in both material and cycle time. Specify 7075-T6 only when the part needs the strength-to-weight ratio. For brackets, housings and fixtures, 6061-T6 is the practical default.

• 6061-T6 — general-purpose alloy, good corrosion resistance, anodizes well, lowest cost per kilogram
• 7075-T6 — aerospace-grade strength, higher cost, harder on end mills and inserts
• 5052-H32 — better for thin sheet and formed parts, less common in solid blocks
• 2024-T3 — high fatigue strength, common in aerospace brackets, does not anodize as cleanly as 6061

See every alloy and finish we machine on the Services & Capabilities page.

Tolerances and Surface Finish Set the Machining Time

Standard tolerance on a cnc machining quote for aluminum is ±0.125 mm (±0.005 in) unless you call out tighter dimensions on the drawing. 6061-T6 tolerances of ±0.05 mm (±0.002 in) are achievable on a 3-axis mill without special fixturing, but expect more setups and a price increase of 15-25%. Anything tighter than ±0.025 mm (±0.001 in) usually means grinding or wire EDM after cnc milling aluminum, not straight milling.

Surface finish works the same way. Standard as-milled finish runs 3.2 µm Ra. Ask for 1.6 µm Ra and a finishing pass adds 10-15 minutes per part. Below 0.8 µm Ra, you're into polishing or bead blasting after machining, which adds a full lead-time day on most jobs. Specify the Ra value on critical faces only — spec the whole part to a fine finish and you pay for it on surfaces nobody will ever see.

Wall Thickness and Part Geometry Affect Machinability

Thin walls chatter. On aluminum, we recommend a minimum wall thickness of 0.8 mm (0.03 in) for pockets under 25 mm deep, and 1.2 mm (0.05 in) once you go deeper. Go thinner and the tool deflects, the wall rings during cutting, and you get chatter marks that fail inspection. Deep pockets also cost more: keep the depth-to-diameter ratio under 4:1 where you can, or expect a slower feed rate and a longer cycle time to hold the wall straight.

• Keep pocket depth under 4x the tool diameter to avoid deflection
• Add a 0.5 mm (0.02 in) minimum internal corner radius — sharp internal corners need EDM or a smaller, slower tool
• Avoid wall thickness under 0.8 mm (0.03 in) unless the part is short and well-supported
• Through-holes machine faster and cheaper than blind holes with a flat bottom

Anodizing and Other Finishes for Aluminum Parts

Aluminum anodizing is the most common finish we quote. Type II anodizing adds corrosion resistance and a color option, and typically adds 2-3 days to lead time. Type III hardcoat anodizing is thicker and harder — better for wear surfaces — but it can close down tight tolerances by 0.01-0.03 mm. Specify hardcoat before you finalize a tight-fit dimension, not after.

Bead blasting before anodizing gives a matte, even surface. Skip it and tool marks show through the anodize layer. Clear anodizing is the fastest and cheapest color option. A custom color — black, blue, red — adds a small upcharge and a longer queue at the anodizer, so build it into your lead-time estimate before you commit to a ship date.

FAQ: CNC Machining Quotes for Aluminum Parts

Quick answers below. For anything else, check the full FAQ.

How fast is a cnc machining quote for aluminum parts?

Upload a STEP file and you get an instant, geometry-based price in seconds — no waiting on a person to review the drawing. Complex parts with tight tolerances or hardcoat anodizing may need a quick check from our engineering team, which usually adds hours, not days.

What's the cheapest aluminum alloy to machine?

6061-T6 is the cheapest common alloy to machine and quote. It cuts fast, doesn't work-harden aggressively, and needs no special tooling. 7075-T6 and 2024-T3 both cost more in material and cycle time.

Does anodizing change my part's tolerance?

Yes. Type II anodizing adds about 0.005-0.01 mm to a surface. Type III hardcoat adds 0.01-0.03 mm. On tight-fit features, ask us to machine oversized before anodizing so the finished dimension lands inside tolerance.

Can I get an instant price without a full drawing?

Yes — a STEP file is enough for an instant price. Add a 2D drawing or a note on critical tolerances and finish if any dimension needs to be tighter than the standard ±0.125 mm (±0.005 in).

Get Your CNC Machining Quote

Aluminum forgives more than steel, but the same rules apply: pick the alloy for the job, hold tolerance only where the part needs it, and decide on anodizing before the tolerance is locked. Upload your STEP file and get an instant CNC machining quote with price and lead time broken down by feature, not just by weight. → Get your instant quote now.