Tooling
Use carbide or PCD inserts with aluminium geometry: high positive rake, sharp polished edges and polished chip grooves. Sharp edges limit built-up edge and keep chips short.
Bar stock for automatic lathes
7075-T6 Precision Ground Aluminium Rod
7075 precision ground rod is high-strength 7075-T6 or T651 bar that has been centreless ground to a tight diameter tolerance, roundness and straightness. It feeds cleanly through the guide bushings of Swiss-type and multi-spindle lathes, so long unattended runs produce consistent parts with less scrap. This guide covers tolerances, properties, sizes and how to machine it well.
- Alloy
- 7075-T6 / T651
- Diameter
- About 4 – 25 mm
- Tolerance
- h7 – h9, or −0.02 mm
- Straightness
- About 0.2 mm per metre
Why grind 7075 rod?
Drawn or extruded rod has a diameter tolerance of several hundredths of a millimetre and may be slightly oval or bowed. That is fine on a conventional lathe with a collet, but a sliding-headstock (Swiss-type) lathe supports the bar in a guide bushing right next to the tool. Any variation in diameter or straightness shows up as chatter, runout, poor surface finish or bars jamming in the loader.
Centreless grinding removes a thin layer from the bar between a grinding wheel and a regulating wheel, without centres. The result is a bar with a tightly controlled diameter, excellent roundness and a fine, uniform surface. Combined with the strength of 7075-T6, it gives a stock that suits small precision parts in medical devices, electronics, optics, aerospace fasteners and automation.
Diameter tolerance, roundness and straightness
Ground bar is normally ordered to an ISO 286 h tolerance (zero plus, minus only) so that it always passes through the guide bushing. Many Swiss-lathe users specify a fixed −0.02 mm limit, which falls between h7 and h8 in the common size range.
| Diameter range (mm) | h7 (mm) | h8 (mm) | h9 (mm) |
|---|---|---|---|
| over 3 to 6 | 0 / −0.012 | 0 / −0.018 | 0 / −0.030 |
| over 6 to 10 | 0 / −0.015 | 0 / −0.022 | 0 / −0.036 |
| over 10 to 18 | 0 / −0.018 | 0 / −0.027 | 0 / −0.043 |
| over 18 to 30 | 0 / −0.021 | 0 / −0.033 | 0 / −0.052 |
| over 30 to 50 | 0 / −0.025 | 0 / −0.039 | 0 / −0.062 |
Typical geometric limits
- Straightness
- About 0.2 mm per metre; tighter on request
- Roundness
- A few micrometres (for example ≤ 0.005 mm) on precision grades
- Surface
- Fine ground finish, free of chatter marks and pick-up
- Ends
- Chamfered on both ends for smooth automatic loading
- Length
- Usually 2.5 m or 3 m bars; cut lengths to match the bar feeder
Measure diameter with a calibrated micrometer at several positions along the bar; checking only one end hides taper.
7075 composition (wt %)
Registered Aluminum Association limits, identical to EN 573-3 (EN AW-7075). The mill certificate reports the actual analysis of each lot.
| Element | Minimum | Maximum | Role in the alloy |
|---|---|---|---|
| Silicon (Si) | — | 0.40 | Impurity; kept low for toughness |
| Iron (Fe) | — | 0.50 | Impurity; forms coarse constituents that cut fatigue life |
| Copper (Cu) | 1.2 | 2.0 | Adds strength and improves stress-corrosion behaviour |
| Manganese (Mn) | — | 0.30 | Minor grain control |
| Magnesium (Mg) | 2.1 | 2.9 | Combines with Zn to form the MgZn2 strengthening phase |
| Chromium (Cr) | 0.18 | 0.28 | Controls recrystallisation and stress-corrosion cracking |
| Zinc (Zn) | 5.1 | 6.1 | Main alloying element |
| Titanium (Ti) | — | 0.20 | Grain refiner |
| Others, each / total | — | 0.05 / 0.15 | |
| Aluminium (Al) | Remainder | About 87 – 91 % |
Mechanical properties: T6 and T651
| Basis | Tensile strength | Yield strength (0.2 %) | Elongation | Hardness |
|---|---|---|---|---|
| T6 / T651, typical | 572 MPa / 83 ksi | 503 MPa / 73 ksi | 11 % | 150 HB |
| Cold-finished rod, ASTM B211 minimum | 530 MPa / 77 ksi | 455 MPa / 66 ksi | 7 % | — |
Minimum values vary with diameter and standard; the certificate for each lot shows the governing figures.
T6 or T651? T651 bar has been stretched after quenching to relieve residual stress. For small-diameter ground rod the difference is modest, but T651 parts drift less after heavy roughing, multiple re-clamping or slotting along one side. Choose T651 for long, slender parts or asymmetric features; T6 is fine for short turned parts.
Corrosion and stress-corrosion. 7075-T6 is less corrosion-resistant than 6061 and can be sensitive to stress-corrosion cracking under sustained tensile stress. Small turned parts are usually anodised, which also improves wear resistance. If parts will be press-fitted or stay under tension in humid service, consider 7075-T73 bar.
Common diameters of 7075 ground rod
| Diameter (mm) | Weight (kg/m) | Typical parts |
|---|---|---|
| 4 | 0.035 | Pins, micro-shafts |
| 5 | 0.055 | Connector pins, electronics |
| 6 | 0.079 | Dowels, valve stems |
| 8 | 0.141 | Sensor housings, spacers |
| 10 | 0.221 | Shafts, bushings |
| 12 | 0.318 | Optical mounts, fittings |
| 14 | 0.433 | Medical-device parts |
| 16 | 0.565 | Pneumatic fittings, sliders |
| 19.05 | 0.801 | 3/4 in imperial parts |
| 20 | 0.883 | Hydraulic and pneumatic fittings |
| 22 | 1.068 | Larger spindles and guides |
| 25 | 1.379 | Housings, nozzles |
Intermediate diameters such as 13.5, 13.8 or 16.8 mm are ground for customers who want the bar close to their finished part diameter, so the outside does not need turning at all. Ground bar can also be pre-turned to a "machine-ready" size before grinding to cut setup time.
How to machine 7075 ground rod on Swiss-type lathes
Coolant
A water-soluble coolant at about 6 – 10 % concentration, or MQL, works well for turning. Use a cutting oil for tapping, thread rolling and reaming to improve thread quality.
Speed
Stable cutting at high spindle speeds (several thousand rpm) is normal on rigid machines. Start conservatively on slender parts and raise speed only after checking runout and finish.
Guide bushing set-up
Adjust the bushing to the actual bar diameter and keep it concentric with the spindle. A ground, round bar allows a close setting, which is where most of the accuracy comes from.
Long slender parts
Use a tailstock or follower support and finish in as few clamping operations as possible. T651 helps parts stay straight after roughing.
Finishing
Deburr and chamfer in the same setup. Machined 7075 takes clear and hard anodic coatings; keep pretreatment consistent to avoid colour variation between batches.
A coarse recrystallised surface layer (sometimes called a coarse-grain ring) can form on extruded 7075 bar. On parts that are anodised without turning the outside, it can show as patchy or "snowflake" patterns. If your parts keep the as-ground surface and will be anodised, ask for bar with a controlled coarse-grain layer depth, for example less than 0.5 mm.
Typical applications
- Medical and dental devices: instrument handles, housings and small structural components
- Electronics and connectors: pins, shells and shielding parts that need strength in small sections
- Optics and photonics: lens barrels, mounts and adjuster screws
- Automation and machine building: sliders, links, guides and bushings
- Aerospace and defence: fasteners, spacers and small fittings where 7075-T6 or T73 is specified
- Sporting and consumer goods: bicycle components, fishing-reel parts and knife hardware
7075 ground rod compared with 6061, 2011 and 7005
| Property | 7075-T6 | 6061-T6 | 2011-T3 | 7005-T6 |
|---|---|---|---|---|
| Typical tensile strength | 572 MPa | 310 MPa | 380 MPa | 350 MPa |
| Machinability (chips) | Very good | Good | Excellent (free-cutting) | Good |
| Anodising response | Good | Excellent | Poor | Good |
| Corrosion resistance | Fair | Good | Poor | Fair–good |
| Best use | High-strength small parts | General parts | High-volume screw-machine parts | Welded tubular parts |
Choose 6061 when strength is not critical and a uniform anodised appearance matters most. Choose 2011 for maximum cutting speed on parts that will not be anodised. 7075 is the choice when a small part must carry high load, resist wear or be made thinner than 6061 allows. For a range of alloys in ground form, see our precision ground bar guide and the 2017 ground bar page.
How to order
- SpecifyAlloy and temper (7075-T6 or T651), diameter and tolerance (h7, h8, h9 or a fixed limit), straightness and length.
- Add requirementsEnd chamfers, coarse-grain layer limit for anodised parts, standard (ASTM B211, EN 754, AMS) and quantity.
- ConfirmWe confirm the offer, inspection plan and delivery terms (EXW, FOB, CIF or DAP).
- Inspect and shipBars are gauged for diameter and straightness, wrapped and packed in wooden cases, and shipped with an EN 10204 3.1 certificate.
References and standards
- ASTM B211 – Aluminum and Aluminum-Alloy Rolled or Cold-Finished Bar, Rod, and Wire
- EN 754-2 – Cold drawn rod/bar and tube: mechanical properties
- ISO 286-2 – Geometrical product specifications: ISO code system for tolerances on linear sizes
- EN 573-3 – Chemical composition and form of wrought products
- ASM International – Properties of Wrought Aluminum and Aluminum Alloys: 7075
7075 precision ground rod: frequently asked questions
Why is ground rod supplied with a minus tolerance?
A minus-only tolerance such as h8 or −0.02 mm means the bar is never larger than nominal, so it always passes through the lathe guide bushing and loader without jamming, while staying close enough for a stable, low-runout fit.
What is the difference between 7075-T6 and T651 ground rod?
Strength is the same. T651 has been stretched to relieve internal stress, so slender or asymmetric parts move less after roughing and re-clamping. For short, simple turned parts T6 is adequate.
Is ground 7075 rod good for anodising?
Yes, it takes clear, black and hard anodic coatings. If the ground surface is left unmachined, specify bar with a shallow coarse-grain layer and keep pretreatment consistent, otherwise patchy appearance can occur.
Which is better for Swiss-type lathes, 7075 or 6061?
6061 is cheaper and anodises more uniformly; 7075 is nearly twice as strong and machines with shorter chips. Choose 7075 for small parts under high load or wear, 6061 for cosmetic or lightly loaded parts.
What diameters are available?
Common stock sizes run from about 4 to 25 mm, including imperial sizes such as 3/4 in (19.05 mm), and intermediate diameters can be ground close to your finished part size on request.
Can you supply an EN 10204 3.1 certificate?
Yes. Each delivery comes with a 3.1 mill certificate showing chemistry and mechanical properties, and dimensional records can be provided on request.
Running 7075 on Swiss-type lathes?
Send the diameter, tolerance, length and annual quantity. We will reply with availability, certification and a delivered price.
