# Aluminum CNC Machining Guide: 6061, 7075 and 5052 Alloy Selection > Aluminum CNC machining guide comparing 6061, 7075, 5052 and related alloys by strength, corrosion resistance, machinability, temper, cost and applications. https://www.sinbo-machining.com/wiki/materials/aluminum/ --- ## On This Page - Which Alloy Do You Actually Need? - Alloy Data at a Glance - T6 vs T651 — This Matters for CNC - 7075 Stress Corrosion Cracking (SCC) - Real Machining Parameters - 6061-T6 (carbide tools) - 7075-T6 (carbide tools) — reduce speed vs 6061 - Surface Treatment Compatibility - Procurement Tips - Common Mistakes # Aluminum Alloys Aluminum is the most machined metal in our shop. But picking the wrong grade is a common mistake — 7075 ordered when 6061 suffices (overpaying 40%), or 2024 specified for a welded assembly (it's not weldable). This page helps you get it right the first time. ## Which Alloy Do You Actually Need? Stop here. Answer this question first — it determines everything else. | Your Situation | Use This | Why | Don't know / general purpose | 6061-T6 | Covers 80% of cases. Machinable, weldable, anodizable, cheap. | Need maximum strength | 7075-T6 | 572 MPa tensile — stronger than mild steel. But not weldable, harder to machine. | Marine / saltwater exposure | 5052-H32 | Best saltwater corrosion resistance of any common aluminum. | Fatigue-critical (cyclic loading) | 2024-T4 | Best fatigue endurance. Used in aircraft skins, wing structures. | European structural projects | 6082-T6 | European equivalent of 6061, slightly stronger. EN 755 certified. | Need to weld after machining | 6061 or 5052 | 7075 and 2024 are NOT weldable. Period. | Electrical / thermal conductor | 1100 or 6061 | Pure aluminum (1100) has best conductivity, 6061 is a good compromise. | Budget is the primary concern | 6061-T6 | Cheapest to buy, fastest to machine, widest availability. ## Alloy Data at a Glance | Property | 6061-T6 | 7075-T6 | 5052-H32 | 2024-T4 | 6082-T6 | Tensile (MPa) | 310 | 572 | 193 | 469 | 340 | Yield (MPa) | 275 | 503 | 145 | 324 | 290 | Elongation | 12% | 11% | 12% | 20% | 10% | Density (g/cm³) | 2.70 | 2.81 | 2.68 | 2.78 | 2.71 | Hardness (HB) | 95 | 150 | 60 | 120 | 100 | Thermal cond. (W/mK) | 167 | 130 | 138 | 121 | 180 | Machinability | Excellent | Good | Excellent | Fair | Excellent | Weldable | Yes | No | Yes | No | Yes | Anodize quality | Best | Fair (dark) | Good | Poor | Good | Relative cost | 1.0x | 1.8–2.5x | 0.9x | 1.5–2.0x | 1.1x ## T6 vs T651 — This Matters for CNC When you order aluminum plate, you'll see both T6 and T651 offered. The difference matters a lot for machining. T6 = solution treated + quenched + artificially aged. The quenching step locks in residual stresses. When you machine material off one side of a T6 plate, the stress imbalance causes warping. T651 = same as T6, but with a controlled stretching operation (1–3% permanent elongation) between quenching and aging. This relieves the residual stress. The result: same mechanical properties, but the plate stays flat after machining. Rule of thumb Always specify T651 when ordering plate for CNC machining. The cost premium is minimal (5–10%), but it prevents warping — especially on thin-walled parts or when removing significant material from one side. T6 is fine for bar stock and tube where the cross-section is uniform. Common mistake Ordering 7075-T6 plate for a large flat bracket, then finding it warped after machining the pocket. This is the #1 aluminum machining problem. Solution: use T651, or add a stress-relief anneal before final machining. ## 7075 Stress Corrosion Cracking (SCC) 7075-T6 is susceptible to stress corrosion cracking in humid or marine environments. If your part will see sustained tensile stress in a corrosive environment, this is a real failure risk. | Temper | Tensile (MPa) | Strength loss vs T6 | SCC resistance | T6 | 572 | Baseline | Poor | T73 | 503 | −12% | Excellent (10x improvement) | T7351 | 503 | −12% | Excellent + stress relieved SCC failure mode Stress corrosion cracking is insidious — the part looks fine, then fails suddenly under load. No visible warning. If you're using 7075 for structural parts in any environment with moisture or salt, specify T73 or T7351. ## Real Machining Parameters These are starting parameters from our shop. Adjust based on your setup, tool condition, and part geometry. ### 6061-T6 (carbide tools) | Operation | Speed (m/min) | Feed | Doc | Notes | Roughing (end mill) | 300–500 | 0.10–0.20 mm/tooth | 1–5mm | Aggressive — 6061 cuts easy | Finishing (end mill) | 500–800 | 0.05–0.10 mm/tooth | 0.2–0.5mm | High speed for good finish | Drilling (φ6–12mm) | 100–150 | 0.08–0.15 mm/rev | — | Peck cycle for deep holes | Tapping | 30–60 | — | — | Use spiral flute taps for blind holes | Face milling | 400–600 | 0.15–0.25 mm/tooth | 1–3mm | 45° lead angle preferred ### 7075-T6 (carbide tools) — reduce speed vs 6061 | Operation | Speed (m/min) | Feed | Doc | Notes | Roughing (end mill) | 200–350 | 0.08–0.15 mm/tooth | 0.5–3mm | 20–30% slower than 6061 | Finishing (end mill) | 350–550 | 0.04–0.08 mm/tooth | 0.1–0.3mm | Harder material, lighter cuts | Drilling | 80–120 | 0.06–0.12 mm/rev | — | More abrasive — check tool wear | Tapping | 20–40 | — | — | Use thread-forming taps if possible Tool wear note 7075 and 2024 contain copper, which makes them more abrasive on carbide tools. You'll see faster flank wear. If you're running a large batch of 7075, budget for more frequent tool changes. Diamond-coated end mills last significantly longer on aluminum — worth the cost for production runs. ## Surface Treatment Compatibility | Treatment | 6061 | 7075 | 5052 | 2024 | 6082 | Key Point | Type II anodize | Best color | Dark, uneven | Good | Poor | Good | 6061 gives the most consistent color | Hard anodize (III) | Excellent | Good | Good | Not recommended | Good | 7075 hard coat is less wear-resistant | Chromate conv. | Yes | Yes | Yes | Yes | Yes | Thin film, paint primer only | Powder coat | Yes | Yes | Yes | Yes | Yes | Needs chromate primer first | Electropolish | Good | Fair | Good | Fair | Good | Not common for aluminum ## Procurement Tips | Tip | Detail | Always specify temper | "6061 aluminum" is incomplete. Always say "6061-T6" or "6061-T651". Different tempers have vastly different properties. | Request mill cert | For critical parts, request the material test report (MTR). Verify the alloy and temper match what you ordered. | Watch for counterfeit 7075 | Some suppliers sell 7A04 as "7075 equivalent" — it's not the same. Insist on ASTM B209 certified material for aerospace parts. | Plate vs extrusion | Plate has more uniform properties across the cross-section. Extrusions can have grain structure variations at the surface. | Storage | Aluminum forms a natural oxide layer — this is normal and protective. No special storage needed. Just keep it dry. | Cost negotiation | Aluminum prices follow the LME (London Metal Exchange). Large orders (>500kg) can negotiate 5–15% off list price. ## Common Mistakes | Mistake | What happens | Correct approach | Specifying 7075 "for strength" when 6061 suffices | Paying 2x material cost + slower machining = 3x total cost for no benefit | Do the stress calculation first. 6061 at 310 MPa handles most loads. | Ordering T6 plate for thin-wall parts | Warps after machining, scrap rate goes up | Use T651. Always. | Welding 7075 or 2024 | HAZ loses most strength, cracks form | Design for mechanical fastening or adhesive bonding | Anodizing 7075 and expecting bright colors | Gets dark brown/gray, color varies across the part | Use 6061 if cosmetic anodizing is needed | Using 7075-T6 in marine environment under load | Stress corrosion cracking — sudden failure | Use T73 temper, or switch to 5052/6061 | Not accounting for anodize thickness on tight features | Part goes oversize after anodize (adds 10–25μm per surface) | Machine undersize by half the anodize thickness before coating