6061 vs 7075 for CNC parts: strength, machining, and finish

This comparison is for a US or EU engineer picking an aluminum grade before an RFQ to a China factory. You are choosing stock that a mill will cut, anodize, and inspect, not a brochure alloy.

If the part is a housing, plate, or bracket with Type II anodize, start at 6061-T6 on aluminum CNC material options. Move to 7075-T6 only when the load case needs the extra yield.

Key takeaways

• Specify 6061-T6 as the default CNC aluminum. Specify 7075-T6 when yield or section size cannot meet the load on 6061.
• Call the temper. 6061 and 7075 without T6 (or another named temper) are not quotable production grades.
• 7075 is stronger. It also takes more tool time and is more likely to move in thin plate after heavy pockets.
• Cosmetic Type II anodize is more even on 6061. 7075 can be used, but color and thickness are less uniform.
• Density and stiffness are close. You do not buy 7075 to make the part “feel stiffer.” You buy it to raise yield in a small section.

6061 vs 7075 for CNC parts: start with this table

6061 vs 7075 for CNC parts should be decided from load, finish, and distortion, in that order.

Factor	6061-T6	7075-T6	Best for	Watch-out
Typical UTS / yield	~310 / 276 MPa	~572 / 503 MPa	7075 when the load case needs it	Typical published ranges, not a PO guarantee
Machining	Fast, low tool wear	Slower, more residual stress in plate	6061 for most CNC parts	7075 pockets can move after roughing
Corrosion	Better in most shop and outdoor air	Worse (zinc/copper-rich)	6061 if coating is light	7075 usually wants anodize or conversion
Type II anodize	Even color, predictable build	More color and thickness scatter	6061 for cosmetic housings	Mask and size fits for 5-25 µm coat
Stock	Common plate and bar	Common, higher stock cost	6061 unless 7075 is required	Confirm temper on the PO
Welding	Weldable in this pair	Generally not welded on CNC parts	6061 if the drawing shows a weld	Do not “just TIG” 7075

Bottom line: specify 6061-T6 unless the drawing’s strength numbers fail without 7075-T6.

On 2026 RFQs, typical published ranges from Aluminum Association alloy data put 6061-T6 near 310 MPa tensile and 276 MPa yield, and 7075-T6 near 572 MPa tensile and 503 MPa yield. Use those figures to choose a grade. Use the mill cert for the lot you buy.

7075-T6 yield is roughly 1.8× 6061-T6 on those handbook numbers. If your 6061 wall already has margin, you do not need that 1.8×. If a 6061 wall would have to grow 3 mm and the envelope cannot grow 3 mm, 7075 is doing a job. “Aircraft aluminum” on the RFQ is not a grade. Write 7075-T6 or do not claim it.

6061 vs 7075 for CNC parts: strength and stiffness

6061 vs 7075 for CNC parts on strength is not close: 7075-T6 is in a different class.

Elongation is often similar (about 10% in many handbook rows), so 7075 is not “more ductile.” Density is close (about 2.70 vs 2.81 g/cm³). Elastic modulus is also close, around 69 GPa. A 7075 bracket of the same geometry is not meaningfully stiffer in bending. It yields later. If deflection is the problem, change section or add ribs. Changing to 7075 to “stop flex” is a common miss.

If a 6061-T6 wall already meets yield with margin, 7075 only adds stock cost, tool time, and finishing risk. If a 6061 wall would have to grow, and you cannot grow it, 7075-T6 is the grade.

Fatigue details depend on product form, grain direction, and surface. Do not treat a handbook UTS as a fatigue table. Plate has different properties in the longitudinal, long-transverse, and short-transverse directions. If you have a real fatigue case, pick the grade from that calculation, then name temper and grain direction (for example T651 plate, long grain along the load). If you do not have that calculation, you do not have a reason to leave 6061.

Shear and bearing at holes follow the same logic. A small 7075 lug can carry what a fatter 6061 lug would carry. If you can fatten the lug, stay on 6061 and keep the anodize even. If the envelope is a 4 mm lug that already failed 6061 yield, 7075-T6 is the honest call.

T651 / T6511 notes matter on plate and extrusion when residual stress and machining movement are in the conversation. If your stress person named T73 or another overaged 7xxx temper for stress-corrosion reasons, write that temper. Do not “upgrade” a T73 drawing to T6 because T6 bar was on the shelf.

Machinability, distortion, and tool path

6061-T6 is the easier CNC aluminum. It cuts with moderate forces, makes a manageable chip, and is friendly to high-speed toolpaths on plates and housings.

7075-T6 is still very machinable compared with stainless or titanium, but it is harder on edges and more likely to show residual-stress movement in plate. A common process is to rough, rest or lightly flatten, then finish. That extra handling belongs in the quote when the part is a thin 7075 plate. A 6 mm 7075 plate with 4 mm pockets can move 0.05 mm or more after heavy hogging even when the program was fine. 6061 can move too. 7075 plate is the usual repeat offender.

Internal radii should match a real end mill (R2 or R3, not a sharp CAD corner). That matters more in 7075 because a tiny tool in a deep pocket will deflect. Custom CNC machining will still cut both grades. The DFM note you want is whether the pocket needs a rest operation. Depth-to-diameter above about 4:1 is where chatter starts, same as any mill job. 7075 does not give you a pass on a 1 mm mill in a 20 mm corner.

Weldability is a split: 6061 is the weldable choice in this pair. 7075 is generally not welded in production CNC parts. If the drawing shows a weld, it is already pointing at 6061, not 7075. Do not specify 7075 and then add a weld note “if needed.” Pick one.

Feeds and tool life are shop details, not RFQ prices. Expect more edge wear on 7075 and a more conservative finish pass on thin floors. Do not put “high speed aluminum” as a process requirement. Put the grade, the wall thickness, and a rest/finish note if the plate is skinny.

CNC milling of both alloys still wants ISO 2768-m on unmarked sizes unless a fit says otherwise. Grade choice does not tighten a title block. A 7075 part with ±0.02 mm on every pocket wall is still an inspection problem.

Corrosion, anodizing, and cosmetic class

6061 takes Type II anodize more evenly. That is why cosmetic enclosures and visible brackets usually stay on 6061-T6.

7075 can be anodized, including Type II and Type III per MIL-A-8625F (1993). Expect more color scatter and a more careful masking plan. Type II build is still in the 5-25 µm range. Call “dimensions before coat” on fits, same as 6061. Anodizing finishing services should see the alloy on the RFQ, not discover 7075 after the dye tank is set for 6061.

For corrosion without a heavy anodize, 6061 is the safer default. 7075 in humid or marine-adjacent service usually wants conversion coating or anodize. Put that note on the drawing. Bare 7075 in a coastal enclosure is a maintenance problem, not a machining flex.

ASME Y14.5-2018 still applies to the size scheme. Alloy choice does not replace datums. Put the finish spec in the notes so the shop does not quote as-machined 7075 when you needed black Type II.

Cosmetic class is a drawing note, not a feeling. If two covers sit on the same panel, specify 6061-T6 for both unless one is a load member. Mixed 6061 and 7075 Type II black on one assembly is how dye lots look like two products. If 7075 is required on the load member, accept a color mismatch or keep that part as-machined / conversion coated.

Type III hardcoat is a wear choice on either alloy. It still has a build that eats fits. Mask or dimension before coat. Do not use Type III to “make 6061 as strong as 7075.” Hardcoat is a surface. Yield is the section.

Decision tree: which grade to specify

Use this tree and stop. Do not leave “aluminum” on the RFQ.

1. Check the load case against typical 6061-T6 yield (~276 MPa). If it passes with your safety factor and section, specify 6061-T6.
2. If it fails and you cannot thicken the section, specify 7075-T6 (or another 7xxx temper your stress person named).
3. If the part is welded, specify 6061-T6 (or another weldable alloy). Do not pick 7075.
4. If the part is a cosmetic Type II housing, prefer 6061-T6. Use 7075 only if step 2 forced it, and accept more color variation.
5. If the part is a thin pocketed plate, prefer 6061-T6. If it must be 7075, add a rest/finish note and a distortion inspection.

Write the result as 6061-T6 or 7075-T6 in the title block, plus product form if grain direction matters. Lock finish type, before/after coat, mill cert if required, and “no weld” on 7075. Do not write “aircraft aluminum” as a substitute for 7075-T6.

Send the drawing through YXT CNC contact if you want a note on whether a 7075 plate pocket needs a rest operation.

Drawing situation	Grade to write	Finish note	Distortion note
Cosmetic box, low load	6061-T6	Type II, even color expected	Standard mill practice
Load lug, envelope locked	7075-T6	Anodize or conversion; color may vary	Watch thin sections
Welded bracket	6061-T6	Match weld and coat plan	Do not substitute 7075
Thin pocketed plate, 6061 OK on stress	6061-T6	Type II if cosmetic	Still check floors after rough
Thin pocketed plate, 7075 required	7075-T6	Before-coat sizes	Rough, rest, finish; inspect flatness
Mixed cosmetic + load in one assembly	6061 + 7075 only if needed	Expect dye mismatch	Split part numbers

Bottom line of this table: 6061-T6 is the default line. 7075-T6 is the exception line you use when yield in a locked envelope says so.

Worked RFQ: 6061 cover vs 7075 load arm

Same buyer, two parts, do not copy the alloy from one title block onto the other.

Part P-55001 electronics cover, 160 × 100 × 12 mm, 6061-T6 plate. Pockets leave 2 mm floors. Type II black 8-12 µm, dimensions before coat, mask 2× Ø6 locating bores. Qty 20 / 100. Load is a lid and four M4 screws. Handbook 6061-T6 yield is enough by a wide margin. RFQ alloy line: 6061-T6 plate. Process note: no 7075 substitute. Inspection: FAI, CMM on datums and the two Ø6 bores. Incoterms belong in the commercial header, not in the alloy choice.

Part P-55002 load arm, 80 × 18 × 12 mm, envelope locked against a larger 6061 section. Stress used typical 7075-T6 yield ~503 MPa. No welds. Grain along the 80 mm length. Type II clear, dimensions before coat, color match to P-55001 is not required. Qty 20 / 100. RFQ alloy line: 7075-T6 plate or bar as stock allows, T6 or T651, mill cert if incoming QA needs it. Process note: rough pockets, rest, finish; inspect arm flatness after finish. Internal radii R3 minimum.

Header pastes:

P-55001 Rev C | 6061-T6 plate | Type II black 8-12 µm before coat | qty 20/100 | no 7075 swap

P-55002 Rev C | 7075-T6 | Type II clear before coat | qty 20/100 | rest after rough | R3 min | no weld

That pair is a clean 6061 vs 7075 for CNC parts decision. The messy version stamps 7075-T6 on both because the load arm is “important,” then wonders why the cover costs more, moves after pocketing, and dyes a different black. Put 7075 where the numbers need it. Put 6061 on the rest.

If purchasing later finds 7075 plate on delay, the cover still must not silently become 7075, and the arm must not silently become 6061. Substitutions are drawing changes. Bump the rev, re-run the yield check, and resend the RFQ header.

FAQ

Is 7075 always better than 6061 for CNC parts?

No. 7075-T6 is stronger. 6061-T6 is usually better for machining, corrosion, welding, and uniform anodize. “Better” on a CNC drawing means the grade that meets the load with the least process pain. If 6061 yield clears the case, 7075 is extra stock cost, extra tool wear, more plate movement, and more anodize scatter. If 6061 yield fails and the envelope cannot grow, 7075 is better because the part can exist. Handbook tensile is not a quality score. It is a selection input. Write the temper either way.

What temper should I specify, T6 or something else?

T6 is the common CNC stock temper for both grades. If you need T73, T651, or another temper, name it. T6 without a product form is still better than “7075” alone. T651 plate is often requested when residual stress and machining movement matter. T73 and other overaged 7xxx tempers show up when stress-corrosion is in the stress report. Do not let purchasing swap T6 for T73 or the reverse to clear a shelf. Strength and corrosion behavior change. Put the temper on the title block and on the RFQ header so the mill cert can be checked against it.

Does 7075 anodize as well as 6061?

It anodizes, but Type II color and thickness are less even than on 6061. Prefer 6061-T6 for cosmetic housings. 7075 Type II can still be specified when the load case forced 7075. Call MIL-A-8625F (1993) type, color, thickness, and before/after size, same as 6061. Warn industrial design that two alloys on one panel may not dye as a pair. Mask fits. Do not use anodize uniformity as a reason to reject 7075 on a lug that 6061 cannot carry. Use it as a reason to keep covers on 6061.

Can I substitute 6061-T6 if 7075-T6 is on backorder?

Only if the drawing’s strength case still passes. Update the title block if you approve the change. A verbal “use 6061 this lot” is how FAI, mill certs, and the next PO disagree. Re-run yield and fastening checks on the 6061 handbook numbers (~276 MPa yield typical). If they fail, wait for 7075 or thicken the section in a new rev. If they pass, bump the revision to 6061-T6, keep the finish notes, and resend the RFQ. Do not mix both grades in one lot of the same part number.

Which grade is better for thin-wall CNC housings?

6061-T6 in most cases. Use 7075-T6 when the wall cannot grow and yield is short on 6061. Thin walls chatter and move after pocketing on both alloys. 7075 plate often moves more. If the housing is cosmetic and lightly loaded, 6061 plus a sensible wall (often 1.5-2 mm class for millable aluminum, geometry depending) is the path. If the housing is a structural shell, run the numbers before you pick 7075 as a shortcut around a 0.8 mm wall that neither alloy will mill cleanly.

Are the MPa numbers in this article guaranteed by the shop?

No. They are typical published ranges. Incoming QA should read the mill certificate for the lot you bought. Shops cut the stock you named. They do not rewrite handbook tensile into a process capability. If you need a minimum yield on the PO, that is a material spec and a cert requirement, not a machining promise. Put EN 10204 3.1 or your company cert language on the RFQ only if you will check it. Then compare the cert to 6061-T6 or 7075-T6, not to this article.

Is 7075 worth it just to reduce wall thickness for weight?

Only if the thinner 7075 section still machines without chatter and still meets buckling and deflection. Weight scales with density, which is close (about 2.70 vs 2.81 g/cm³), so you do not save mass by swapping grade at the same geometry. You save mass only if you actually shrink the section. A 7075 wall that is 1.0 mm and 15 mm tall may cost more in scrap than it saves in grams. Check millable height-to-thickness, then check yield. If both pass, 7075 can be a weight tool. If the wall is already 6061-feasible, stay on 6061.

Can I call out “aerospace aluminum” instead of 6061 or 7075?

No. Write 6061-T6 or 7075-T6 (or the exact temper your stress person named). “Aerospace aluminum” is not a purchasable grade and not a finish spec. Translate that phrase to a real alloy and temper before you RFQ a China factory. The estimator will otherwise pick common 6061-T6 stock, and your incoming cert will not match the story in your head.