By Phil Huang, Elite Mold Tech. Updated November 2, 2026.
6061 is the default aluminum for CNC parts. It gives good strength, cuts cleanly, welds well, and anodizes evenly. Typical 6061-T6 has a tensile yield strength of 276 MPa and an ultimate strength of 310 MPa. Use it for brackets, housings, frames, and general structural parts. This guide covers the properties, the T6 and T651 tempers, stock forms, tolerances, finishes, and when to pick a different alloy.
If you are unsure which aluminum to pick, start with 6061 and change only when the job demands more strength or a special property.
Key takeaways
- 6061-T6 has a typical yield strength of 276 MPa (40 ksi) and a density of 2.70 g/cm³.
- T651 is T6 with a stretch step that relieves stress, so plate warps less during machining.
- Our standard tolerance on aluminum is ±0.125 mm (±0.005 in), with tighter limits on request.
- 6061 anodizes evenly and welds well, which 7075 does not do as easily.
- Choose 7075 only when you need the extra strength, because it costs more to machine.
What is 6061 aluminum, and why is it so common for CNC machining?
6061 is a heat-treatable aluminum alloy with magnesium and silicon, and it is the most common choice for CNC machined aluminum parts because it balances strength, cost, and cutting behavior (Elite Mold Tech, 2026). It is easy to buy in sheet, plate, bar, and extrusion forms, it machines well, and it takes a finish without fuss.
Three traits explain its popularity:
- It machines cleanly. Chips break well and tools last. See our guide to the machinability rating of aluminum for how it compares.
- It welds. That helps frames and assemblies built from several pieces.
- It anodizes evenly. Color looks uniform across the part.
It is one of the grades on our aluminum CNC machining service page, alongside 6063, 6082, 5052, 5083, 2024, and 7075.
What are the mechanical properties of 6061-T6?
6061-T6 has a typical tensile yield strength of 276 MPa (40 ksi), an ultimate tensile strength of 310 MPa (45 ksi), and 17% elongation (Protolabs, 2026). Its density is 2.70 g/cm³, which is about one third the weight of steel.
Propiedad | 6061-T6 (typical) |
Tensile yield strength | 276 MPa (40 ksi) |
Resistencia a la tracción | 310 MPa (45 ksi) |
Elongation | 17% |
Brinell hardness | 95 |
Densidad | 2.70 g/cm³ (0.098 lb/in³) |
Modulus of elasticity | 68.3 GPa |
Shear strength | 207 MPa (30 ksi) |
Source: Protolabs aluminum 6061-T651/T6 data sheet (2026). Typical values, not guaranteed minimums. Ask for the mill certificate if your part needs proof.
Our own table lists the same yield value of 276 MPa, a fatigue strength of 96 MPa, and a Brinell hardness of 95 (Elite Mold Tech, 2026). Treat all these figures as typical. Real values change with the lot, the size, and the temper.
What is the difference between 6061-T6 and 6061-T651?
6061-T651 is 6061-T6 that has also been stretched after heat treatment to relieve internal stress, which reduces warping when you cut it (Xometry, 2026). Both start with the same T6 heat treatment, so their strength is close. The difference is stability, not strength.
Temper | What it is | Common form | Lo mejor para |
T6 | Solution heat treated and aged | Sheet, thin stock | Thin, small parts |
T651 | T6 plus stress relief by stretching | Plate, 0.25 in and thicker | Flat parts with large pockets, tight flatness |
T6511 | T6 plus stress relief, plus straightening if needed | Extruded bar and rod | Long, constant-profile parts |
Source: Xometry, “6061-T651 vs T6 and T6511” (2026). Product forms are typical, not strict rules.
Here is how to choose in practice:
- Large flat plate parts: pick T651. Cutting away a lot of material from stressed plate lets it move.
- Thin or small parts: T6 is fine and easier to find.
- Long profiles: T6511 extrusion costs less than plate.
We list both 6061 and 6061-T6 on our site, but not 6061 T651 or T6511 by name, so confirm the plate temper before you order. Tell us the temper on your drawing, or ask us to pick one at quote. Our guide to aluminum tempers explains every code.
What tolerances can you hold on 6061 aluminum CNC machining?
Our standard tolerance on aluminum parts is ±0.125 mm (±0.005 in), and we can hold ±0.025 mm (±0.001 in) on critical features on request (Elite Mold Tech, 2026). The alloy itself holds tolerance well, because 6061 is stable and cuts without much springback.
- Minimum wall: 0.75 mm on our aluminum table.
- Minimum feature size: about 0.5 mm (0.020 in).
- Standard surface: Ra 3.2 μm (125 μin) as machined.
Tolerance depends on the feature, not just the alloy. Long thin walls and deep pockets move more than short blocks. Read our guide to aluminum CNC machining tolerances for the full picture, and mark only the dimensions that need tight limits.
What stock forms does 6061 aluminum CNC machining use?
6061 is sold as sheet, plate, bar, rod, and extrusion. The form changes cost, waste, and warping risk. Pick the form that is closest to your finished part, so you cut away less material.
- Plate: best for large flat parts and fixtures. T651 plate keeps its shape better.
- Bar and rod: best for round and compact parts, including turned parts.
- Extrusion: best for long parts with a fixed profile.
- Sheet: best for thin parts that are cut or bent rather than milled.
Our site does not list the stock sizes we hold, so ask us at quote what is on the shelf for your size. Our largest aluminum part size is 200 x 80 x 100 cm.
How does 6061 take a finish?
6061 anodizes evenly, which makes it the usual choice for colored and protected parts. We offer anodizing, powder coating, and polishing in house for aluminum parts (Elite Mold Tech, 2026). Type II anodizing is available in black, red, blue, gold, and clear.
Finish and tolerance go together. Anodizing adds a thin layer, so tight holes and threads need allowance. Our guide to aluminum CNC surface finishes compares every option, and our page on Type II anodizing shows colors.
When should you choose 6061 and when should you not?
Choose 6061 for most general parts. Choose another alloy when strength, weight, or cutting speed matters more. The table shows common swaps.
If you need | Consider | Por qué |
General strength, welding, anodizing | 6061 | Balanced and easy to source |
Highest strength for the weight | 7075 | Much stronger, harder on tools, more cost |
Faster cutting, lower tool wear | 2011 or similar | Free-machining grade |
Extruded shapes and good looks | 6063 | Soft, smooth, common in extrusions |
Formed or bent sheet parts | 5052 | Better formability |
Read the full comparison in our guide to 6061 vs 7075 aluminum, and our guide to aluminum alloys for CNC machining for the wider list.
What design tips help 6061 parts machine well?
Good design keeps cutting time low and holds shape. The same rules apply to every aluminum grade, but they matter most on thin 6061 parts.
- Keep walls above the minimum. Our aluminum table lists 0.75 mm, and thicker walls cut with less chatter.
- Use generous inside corners. Larger radii let a bigger tool cut faster.
- Limit deep, narrow pockets. They need long tools and slow passes.
- Name the temper and finish. That lets us plan stock and coating allowance together.
Our aluminum CNC design guidelines cover each rule in detail.
What does 6061 cost to machine?
6061 is among the lower-cost aluminum alloys to machine, because it cuts fast and the raw stock is easy to buy. We do not publish a price per part, because cost depends on size, features, finish, and quantity. Our site rates aluminum machining at the lowest price band.
- Machine time: the biggest driver, set by part shape.
- Stock form: plate costs more than extrusion for the same part.
- Finish: anodizing and coating add steps.
- Tolerance: tighter limits add inspection time.
See our guide to aluminum CNC machining cost for the full breakdown. Send a drawing for a real number.
Get your 6061 parts quoted
Send your 3D file and 2D drawing, and tell us the temper if it matters. Our engineers will check the design, flag anything that raises cost, and quote the part. We guarantee a response within 12 hours, and lead time is under 10 days for most orders, depending on alloy availability, part complexity, and finish.
¿Listo para empezar? Solicitar un presupuesto or visit the Elite Mold Tech home page.
Preguntas frecuentes
Q: What is 6061 aluminum used for?
A: It is used for brackets, housings, frames, and general structural parts. It is the default aluminum for CNC machined parts because it balances strength, cost, and ease of cutting.
Q: Is 6061-T6 the same as 6061-T651?
A: They share the same T6 heat treatment. T651 is also stretched to relieve stress, so it warps less when you cut it. T651 is usually plate, and it costs more.
Q: How strong is 6061-T6 aluminum?
A: Typical values are 276 MPa (40 ksi) yield strength and 310 MPa (45 ksi) ultimate strength. These are typical figures, so ask for a mill certificate if you need proof.
Q: Can 6061 be anodized?
A: Yes. 6061 anodizes evenly. Type II anodizing comes in black, red, blue, gold, and clear. Tell us the finish early so we plan the final size around the coating.
Q: Is 6061 or 7075 better for CNC machining?
A: 6061 is easier and cheaper to machine. 7075 is much stronger. Use 6061 unless your part needs the extra strength. Our comparison guide covers the details.
Q: What tolerance can you hold on 6061?
A: Our standard tolerance is ±0.125 mm (±0.005 in). We can hold ±0.025 mm (±0.001 in) on critical features on request. Mark only the dimensions that need tight limits.
Sources
- Protolabs, Aluminum 6061-T651/T6 CNC Material Data Sheet (2026): protolabs.com
- Xometry, 6061-T651 vs T6 and T6511: xometry.com
- Elite Mold Tech, Aluminum CNC Machining capability tables (2026): elitemoldtech.com/aluminum-cnc-machining
