Choosing the right bar for a job is mostly a trade-off between strength, wear, weight, moisture, chemicals and machining. This quick guide compares the seven materials we stock as round bar. Every material links through to its collection, where you can filter by diameter. We also offer a free cutting service if you need a different length.
At a glance
| Material | Best known for | Good for | Watch out for |
|---|---|---|---|
| HDPE (PE500) | Tough, light, chemical resistant | Bushes, rollers, spacers, guides, wear strips, jigs | Softer than acetal or nylon, so not for high loads |
| Acetal (POM-C) | Stiff, precise, low friction | Gears, slideways, pump and valve parts, precision parts | Continuous use up to about 85°C |
| Nylon 6 (PA6) | Wear resistant and strong | Pulleys, bearings, rollers, gears, bushings, wear pads | Absorbs more moisture than acetal, so allow for size change in damp conditions |
| Aluminium 6082-T6 | Strong and light | Turned and milled parts, shafts, spacers, fixtures | Not recommended for marine use |
| Mild steel EN3B | Bright drawn and weldable | Shafts, spindles, axles, brackets, general fabrication | Will rust, and is not for corrosive or marine environments |
| Brass CZ121 | Free-cutting, very easy to turn | Fittings, valves, turned parts, model engineering | Not recommended for cold working |
| Stainless 303 | Free-machining stainless | Shafts, bolts, fittings, bushings, gears | Corrosion resistance is good in mild environments, not extreme ones |
Which one should I choose?
- Sliding, rubbing or low-friction parts: acetal or nylon. Acetal holds its size better in damp conditions, while nylon is a good choice where wear resistance matters most.
- Wet, damp or chemical environments: HDPE or acetal. Both take up very little water, and HDPE resists many acids, alkalis and solvents.
- Light but strong metal parts: aluminium 6082-T6.
- Welding or fabricating a frame, shaft or bracket: mild steel EN3B, which is weldable and can be case-hardened.
- Lots of turning on a lathe or CNC: brass CZ121 or stainless 303. Both are free-machining grades.
- Lightweight packing, guides and jigs: HDPE. It is lighter than water and machines with standard tools.
The materials in more detail
HDPE (PE500)
A tough, lightweight engineering plastic with a smooth, low-friction surface. It resists many common acids, alkalis and solvents, absorbs very little moisture and is lighter than water. It turns, drills, mills and saws with standard tools. Typical uses are bushes, rollers, spacers, guides, wear strips, jigs and fixtures.
Acetal (POM-C)
Combines high strength and stiffness with low friction and excellent creep resistance, so parts keep their shape under sustained load. It absorbs virtually no moisture, so it stays accurate in wet or humid conditions. Continuous service temperature is -29°C to 85°C. Typical uses are gears, slideways, pump parts, valve bodies and general precision machining.
Nylon 6 (PA6)
One of the most widely used engineering plastics, valued for wear resistance, strength and a low-friction, self-lubricating surface. It resists oils, fuels and many solvents, and is rated for continuous use up to 90°C. Nylon takes up more moisture than acetal, so allow for a small change in size if the part will live in damp conditions. Typical uses are pulleys, bearings, rollers, gears, bushings and wear pads.
Aluminium 6082-T6
A strong, versatile engineering alloy that machines cleanly and has good corrosion resistance. It is one of the strongest alloys in the 6000 series, at a fraction of the weight of steel (density about 2.71 g/cm³, tensile strength about 310 MPa). Typical uses are turned and milled parts, shafts, spindles, spacers, jigs and fixtures.
Mild steel EN3B
A bright drawn low-carbon mild steel with close dimensional tolerances and a smooth finish. It machines cleanly, welds with MIG, TIG and arc processes and can be case-hardened for wear resistance. It is not recommended for high-tensile, marine or corrosive environments. Typical uses are shafts, spindles, rollers, axles, brackets and general turned parts.
Brass CZ121
The most widely used free-cutting brass. The lead content breaks the chips and lubricates the cut, so it turns beautifully on CNC and manual lathes. Corrosion resistance is good to excellent and tensile strength is about 385 MPa. It is suitable for hot forging, turning and knurling, but not for cold working. Typical uses are turned components, fittings, valves and model engineering.
Stainless steel 303
The most free-machining of the stainless steels, which makes it a popular choice for turning and milling where tight tolerances are needed. It has good corrosion resistance in mildly corrosive environments and can be welded using Alloy 310 electrodes. Typical uses are shafts, nuts and bolts, fittings, gears, screws and bushings.
Shop stainless steel round bar
Need a different size or length?
Every bar collection can be filtered by diameter, and we offer a free cutting service for other lengths. If you are not sure which material suits your job, get in touch and we will help you choose.
This guide is general information to help you choose. Always check that a material suits your specific load, temperature and environment before use.