Machining
Use sharp, polished carbide tools with high positive rake, high spindle speeds and flood coolant or mist. 6061-T651 forms short chips; O temper is gummy and should be avoided for machining.
General-purpose machining block
6061 Aluminium Block
6061 aluminium block is the default stock for machined parts that need good strength, stable machining, weldability and corrosion resistance at a reasonable price. It is cut from stretched 6061-T651 thick plate or, for very large sections, made as compression-stress-relieved T652 forged block. Metline supplies 6061 block saw-cut or milled to your sizes, certified to ASTM, AMS and EN, worldwide.
- Alloy
- 6061 (Al-Mg-Si-Cu)
- Tempers
- T651, T652, T6
- Thickness
- Approx. 25 – 200 mm plate; larger forged
- Standards
- ASTM B209 · AMS 4027 · EN 485
What is 6061 aluminium block?
A 6061 block is a thick rectangular piece of 6061 cut from plate or forged to shape, bought as raw stock for CNC machining. Because it is the most widely produced heat-treatable aluminium alloy, 6061 block is easy to source in most sizes, machines predictably and can be welded or anodised after machining.
For blocks up to about 150 – 200 mm thick, the usual source is 6061-T651 plate. The "51" means the plate was stretched by roughly 1.5 – 3 % after quenching, which removes most of the quench stress. Without that step, a thick block would bow as material is removed from one side. Above the practical plate range, open-die forged blocks are used; they cannot be stretched, so they are compressed instead (T652) to achieve the same effect.
A third option, cast and precision-milled tooling plate, is sometimes offered as a "6061 alternative". Cast plate is flatter and more stable but weaker. Choose it for flat base plates and fixtures where strength is secondary, and choose wrought 6061-T651 when the part carries real load.
6061 chemical composition (wt %)
| Element | Minimum | Maximum |
|---|---|---|
| Silicon (Si) | 0.40 | 0.80 |
| Iron (Fe) | — | 0.70 |
| Copper (Cu) | 0.15 | 0.40 |
| Manganese (Mn) | — | 0.15 |
| Magnesium (Mg) | 0.80 | 1.20 |
| Chromium (Cr) | 0.04 | 0.35 |
| Zinc (Zn) | — | 0.25 |
| Titanium (Ti) | — | 0.15 |
| Others, each / total | — | 0.05 / 0.15 |
| Aluminium (Al) | Remainder |
Aluminum Association limits, identical to EN AW-6061 in EN 573-3.
Mechanical and physical properties of 6061 block
Thick sections cool more slowly when quenched, so specified minimums for T651 plate decrease with thickness. Typical values are for moderate thicknesses; the certificate for each block lot gives the tested values for that plate.
| Temper / basis | Tensile strength | Yield strength (0.2 %) | Elongation | Hardness |
|---|---|---|---|---|
| T651, typical | 310 MPa / 45 ksi | 276 MPa / 40 ksi | 12 % | 95 HB |
| T651, specified minimum (moderate thickness) | 290 MPa / 42 ksi | 240 MPa / 35 ksi | ≈ 6 – 10 % | — |
| T651, very thick plate | Lower minimums by thickness band | Lower minimums | — | — |
| O (annealed) | 125 MPa / 18 ksi | 55 MPa / 8 ksi | 25 % | 30 HB |
Typical physical properties (T6 / T651)
- Density
- 2.70 g/cm³
- Modulus of elasticity
- 68.9 GPa
- Thermal conductivity
- 167 W/m·K
- Electrical conductivity
- ≈ 43 % IACS
- Coefficient of thermal expansion
- 23.6 µm/m·°C (20 – 100 °C)
- Melting range
- 582 – 652 °C
Plate-cut, forged and tooling-plate blocks
| Type | Temper | Typical size range | Best for |
|---|---|---|---|
| Plate-cut block | T651 | Approx. 25 – 200 mm thick | Most machined parts; fastest and most economical |
| Forged block | T652 | Larger sections to drawing | Very thick or heavy parts needing wrought properties in all directions |
| Cast tooling plate | Cast, stress-relieved | Precision-milled thickness | Flat base plates, jigs, fixtures where strength is secondary |
| Extruded bar block | T6511 | Smaller sections | Small parts and long blanks |
6061 block sizes and weights
Supply range
- Thickness
- Approx. 25 – 200 mm from plate; larger forged
- Width and length
- Cut to size, typically from plate up to about 2000 mm wide
- Cutting
- Saw cut with clean-up allowance; six-side milled blocks on request
- Surface
- Mill finish or milled; film or wrapping on request
- Marking
- Alloy, temper and lot on each block
Weight in kg = thickness × width × length (mm) × 2.70 ÷ 1,000,000.
| Block size (mm) | Weight (kg) |
|---|---|
| 50 × 100 × 200 | 2.70 |
| 50 × 300 × 300 | 12.15 |
| 75 × 200 × 400 | 16.20 |
| 100 × 200 × 300 | 16.20 |
| 100 × 300 × 500 | 40.50 |
| 150 × 300 × 600 | 72.90 |
| 200 × 400 × 600 | 129.60 |
| 250 × 500 × 1000 | 337.50 |
| 300 × 600 × 1200 | 583.20 |
Tolerances, flatness and inspection
- Saw-cut blocks carry a small positive allowance (commonly +1 to +3 mm) for clean-up; milled blocks to ±0.1 mm or as specified
- Parent-plate thickness and flatness per ASTM B209 / ANSI H35.2 or EN 485-3
- Ultrasonic testing to AMS-STD-2154 or EN 10308 for critical parts, on request
- Hardness or conductivity check to confirm temper
- EN 10204 3.1 mill certificate traceable to the plate or forging lot
Tip: if you are machining deep pockets from one face of a thick block, ask for the block to be cut with the rolling direction along the longest dimension of the part. It does not change strength much in 6061, but it does make distortion more predictable.
Machining, welding and finishing 6061 block
Distortion control
Rough all faces, let the part rest, then finish. Balance pockets on both sides where possible.
Welding
TIG or MIG with 4043 or 5356 filler. Expect strength loss in the heat-affected zone.
Anodising
Excellent response, including hard anodising for wear surfaces and black anodising for optical parts.
Vacuum use
Common for vacuum chambers and semiconductor parts because it machines cleanly and has low outgassing once cleaned.
Corrosion
Good in air and fresh water; anodise or paint for marine exposure.
Where 6061 block is used
- Automation and machinery: manifolds, housings, base plates, robot grippers and fixtures
- Semiconductor and vacuum: chamber bodies, lids and wafer-handling parts
- Moulds: prototype and short-run injection moulds, blow moulds and vacuum-forming tools
- Transport: brackets, suspension parts and EV components machined from solid
- Optics and electronics: camera bodies, heat-spreading housings and instrument frames
- Racing and sport: billet parts for motorsport, cycling and firearms accessories
6061 block compared with 7075, 2024 and 5083 block
| Property | 6061-T651 | 7075-T651 | 2024-T351 | 5083-H111 |
|---|---|---|---|---|
| Typical tensile strength | 310 MPa | 572 MPa | 470 MPa | 290 MPa |
| Machinability | Very good | Excellent | Very good | Fair |
| Weldability | Good | Poor | Poor | Excellent |
| Corrosion resistance | Very good | Fair | Fair | Excellent |
| Relative cost | Low | High | High | Moderate |
6061 is the right default. Move to 7075 when the part needs hardness and strength, to 2024 for fatigue, and to 5083 for marine or cryogenic service and welded structures. See also 6061 plate vs MIC-6 tooling plate.
How to order 6061 block
- SpecifyAlloy and temper, block dimensions, finish (saw-cut or milled), quantity, and the governing standard (ASTM B209, AMS 4027 or EN 485). Attach a drawing if the material will be cut or machined to shape.
- QuoteWe confirm availability, tolerances, certification and delivery terms (EXW, FOB, CIF or DAP) for your destination.
- ProcessMaterial is cut to length or size on request, marked for traceability and inspected for dimensions and surface.
- DocumentEach lot ships with a mill test certificate to EN 10204 3.1 showing chemistry and mechanical results; third-party inspection can be arranged.
- ShipExport packing in seaworthy wooden cases or on pallets with moisture protection, by sea or air to your port or door.
References and standards
- ASTM B209 – Aluminum and Aluminum-Alloy Sheet and Plate
- SAE AMS 4027 – Aluminum Alloy Sheet and Plate, 6061-T6 / T651
- ASTM B247 – Aluminum and Aluminum-Alloy Die Forgings, Hand Forgings, and Rolled Ring Forgings
- EN 485-2 – Sheet, strip and plate: mechanical properties
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits
6061 aluminium (aluminum) block: frequently asked questions
What temper should I order for a 6061 block?
T651 for plate-cut blocks and T652 for forged blocks. Both are stress-relieved, so the block stays stable during machining. Plain T6 thick sections can distort.
How strong is a 6061-T651 block?
Typical values are about 310 MPa tensile and 276 MPa yield. Specified minimums fall slightly with thickness; the certificate gives the tested results.
How do I calculate the weight of a 6061 block?
Multiply thickness × width × length in mm by 2.70 and divide by 1,000,000. A 100 × 200 × 300 mm block weighs about 16.2 kg.
Is 6061 block suitable for moulds?
Yes, for prototype and short-run moulds. For longer runs or harder surfaces, 7075-T651 or mould steel is a better choice.
Can you mill blocks to finished size?
Yes. Blocks can be saw-cut with an allowance or milled on all six faces to tighter tolerances on request.
Do you ship 6061 blocks internationally?
Yes. Metline supplies 6061 blocks worldwide with mill certificates and export packing.
Need 6061 blocks cut to size?
Send the sizes, quantity, temper and finish. We will reply with availability and a delivered price.
