Tooling
Sharp carbide or coated HSS with high positive rake. Polished rake faces reduce built-up edge.
Bar guide
2017 T4 / T451 Precision Ground Aluminium Bar
2017 precision ground bar is Al-Cu-Mg round bar in T4 or T451 temper that has been centreless ground to a tight ISO tolerance such as h8 or h9, ready for bar feeders on CNC and Swiss-type lathes. It combines about 380 – 430 MPa tensile strength with good machinability and a consistent diameter that keeps collets gripping and parts in size. This guide covers tolerances, properties, sizes and machining practice.
- Alloy
- 2017 / 2017A
- Tempers
- T4 · T451 (T651 on request)
- Diameter
- about Ø6 – Ø100 mm
- Tolerance
- h7 · h8 · h9 (ISO 286)
What is precision ground bar, and why 2017?
Ordinary extruded or drawn bar has a diameter tolerance of several hundredths of a millimetre and may be slightly oval or bent. Precision ground bar is passed through a centreless grinder after straightening, which brings the diameter into a narrow ISO tolerance band, improves roundness and leaves a fine, uniform surface.
That matters on automatic lathes. A Swiss-type (sliding headstock) machine supports the bar in a guide bush close to the cutting tool; if the bar diameter varies, the bush either binds or lets the bar chatter. Ground bar feeds smoothly at high speed, so turned parts hold size and surface finish over long runs.
2017 is chosen for ground bar because it is a strong, free-cutting Al-Cu-Mg alloy that produces short chips in T4, holds threads well and costs less than 2024 or 7075. It is popular for screws, pins, connectors, pneumatic fittings and small precision parts. T451 is the stress-relieved (stretched) version, which stays straighter when a large share of material is removed.
ISO 286 tolerance grades for ground bar
Ground bar is ordered to an ISO 286 shaft tolerance. The "h" position means the upper limit is the nominal size and all tolerance is negative, which suits bar that must enter a guide bush or collet of nominal size.
| Diameter (mm) | h7 | h8 | h9 |
|---|---|---|---|
| > 3 – 6 | 0 / −0.012 | 0 / −0.018 | 0 / −0.030 |
| > 6 – 10 | 0 / −0.015 | 0 / −0.022 | 0 / −0.036 |
| > 10 – 18 | 0 / −0.018 | 0 / −0.027 | 0 / −0.043 |
| > 18 – 30 | 0 / −0.021 | 0 / −0.033 | 0 / −0.052 |
| > 30 – 50 | 0 / −0.025 | 0 / −0.039 | 0 / −0.062 |
| > 50 – 80 | 0 / −0.030 | 0 / −0.046 | 0 / −0.074 |
| > 80 – 120 | 0 / −0.035 | 0 / −0.054 | 0 / −0.087 |
Typical ground-bar specification
- Tolerance
- h9 standard; h8 and h7 on request
- Straightness
- Agreed on order; tighter than drawn bar, typically specified per metre
- Surface
- Centreless ground, bright, free of chatter marks and scratches
- Ends
- Chamfered on both ends for smooth bar-feeder loading
- Lengths
- About 1 – 3 m, with 2.5 m and 3 m common for bar feeders; cut lengths to order
- Documents
- EN 10204 3.1 mill certificate and dimensional inspection report
2017 composition (wt %)
| Element | 2017 | 2017A |
|---|---|---|
| Copper (Cu) | 3.5 – 4.5 | 3.5 – 4.5 |
| Magnesium (Mg) | 0.40 – 0.8 | 0.40 – 1.0 |
| Manganese (Mn) | 0.40 – 1.0 | 0.40 – 1.0 |
| Silicon (Si) | 0.20 – 0.8 | 0.20 – 0.8 |
| Iron (Fe) | ≤ 0.7 | ≤ 0.7 |
| Chromium (Cr) | ≤ 0.10 | ≤ 0.10 |
| Zinc (Zn) | ≤ 0.25 | ≤ 0.25 |
| Ti / Zr + Ti | Ti ≤ 0.15 | Zr + Ti ≤ 0.25 |
| Aluminium | Remainder | Remainder |
Mechanical properties of 2017 T4 / T451 bar
| Basis | Tensile strength | Yield strength | Elongation |
|---|---|---|---|
| ASTM B211, 2017-T4 / T451 cold-finished bar, minimum | 379 MPa (55 ksi) | 221 MPa (32 ksi) | 12 % |
| GB/T 3191, 2017 T4 extruded bar, minimum | 345 MPa | 215 MPa | 12 % |
| Typical values, T4 | about 425 MPa | about 275 MPa | about 20 % |
Minimums depend on diameter band and standard; the mill certificate reports actual results for each lot. Hardness is typically around 105 HB in T4. Density is 2.79 g/cm³, so a 1 m bar of Ø13 mm weighs about 0.37 kg.
Coarse grain rings, surface and inspection
Extruded 2xxx bar can form a peripheral coarse-grain ring during solution treatment. On a ground or turned surface it may show up as white spots or a mottled appearance after anodising, and it lowers fatigue strength at the surface. For precision parts, buyers often limit the ring depth (for example to 0.5 mm) and ask for a macro-etch check.
- Diameter measured at several points along the bar and around its circumference
- Straightness checked on a reference table
- Surface inspected for chatter, scratches and grinding burn
- Coarse grain ring depth checked by macro-etch when specified
- Chemistry and tensile tests on each lot
Machining 2017 ground bar
Chips
T4 gives short, broken chips; chip breakers help on long turning passes.
Threads
Cuts and rolls clean threads; 2017 holds thread form better than soft 6xxx alloys.
Stability
T451 limits distortion of long, slender parts; use light finishing passes.
Anodising
Takes decorative and hard anodising, but colour may be less even than on 6xxx alloys; control the process.
Joining
Not suited to fusion welding; parts are threaded, pressed or bonded.
2017 ground bar compared with other alloys
| Property | 2017 / 2017A T4 | 2024 T351 | 2011 T3 | 6061 T6 |
|---|---|---|---|---|
| Strength | High | Higher | Medium–high | Medium |
| Machinability | Very good | Good | Excellent (free-cutting) | Good |
| Corrosion resistance | Fair | Fair | Fair | Good |
| Weldability | Poor | Poor | Poor | Good |
| Typical use | Screws, pins, fittings | High-load parts | High-volume turned parts | General parts, anodised |
Applications
- Fasteners and threaded parts: screws, studs, nuts and pins
- Pneumatics and hydraulics: fittings, valve spools and connectors
- Aerospace and defence: small machined hardware to drawing
- Electronics and instruments: shafts, spacers and connector bodies
- Automotive and general machinery: high-volume turned components
References and standards
- ISO 286-2 – Geometrical product specifications: ISO code system for tolerances on linear sizes (tables of tolerance classes)
- ASTM B211/B211M – Rolled or cold-finished aluminium-alloy bar, rod and wire
- EN 754-2 – Cold drawn rod/bar and tube: mechanical properties
- GB/T 3191 – Aluminium and aluminium alloy extruded bars
2017 precision ground aluminium (aluminum) bar: FAQ
Is there a difference between 2017 and 2017A?
They are very close. 2017A is the European grade with a wider magnesium range and a combined Zr + Ti limit; properties are similar and many drawings accept either.
Why choose precision ground bar instead of regular bar?
Grinding gives a tight, consistent diameter and roundness, so the bar feeds smoothly through guide bushes and collets on automatic lathes and parts hold size.
What tolerance does ground bar have?
Usually h9 to ISO 286, with h8 or h7 on request. For a 13 mm bar, h9 is 0 / −0.043 mm and h8 is 0 / −0.027 mm.
Can 2017 aluminium be welded?
Fusion welding is not recommended because of hot cracking. Resistance or friction welding is possible in some cases, but most parts are joined mechanically.
Is 2017 suitable for anodising?
Yes, but copper makes the colour less uniform than on 6xxx alloys, so process control matters.
Are samples available?
Short sample bars can be arranged for trial machining; tell us the diameter and tolerance you need.
Need 2017 ground bar for your lathes?
Send diameter, tolerance grade, length, temper and quantity. We reply with availability, inspection documents and a delivered price.
