Brass rods in round, hex and square sections

Extruded rod is made by pushing a hot billet through a die, then usually cold drawing it to final size and straightening it. The chemistry is controlled at the billet stage, the cross section is consistent along the length, and the bar comes out straight enough to feed an automatic lathe without chatter.

Commercial rod is the trade's name for rod made largely from recycled brass, with a wider spread of copper, lead and iron. It is cheaper and perfectly usable for many hand-turned or non-critical parts. Where it lets people down is on high-speed automats, where variable lead content changes chip breaking from bar to bar, and on parts that will be plated, where inclusions show through. If your part has a drawing tolerance and a plating finish, ask for extruded rod and a test certificate.

Free-cutting brass is a copper–zinc alloy with roughly 2.5 to 3.5 percent lead added. The lead does not dissolve in the brass. It sits as tiny droplets that break each chip into small curls, lubricate the tool edge and let the bar run at very high spindle speeds. C36000 is the reference material for machinability, rated at 100, and other metals are rated against it.

In India the governing standard is IS 319, Free Cutting Brass Bars, Rods and Sections, which has two grades. Abroad you will see C36000 to ASTM B16 on American drawings and CuZn39Pb3 (CW614N) on European ones. They are close cousins rather than identical alloys: CuZn39Pb3 runs a little lower in copper than C36000, as the table below shows. If your customer's drawing names one of them, match that exact grade.

Choose the section that leaves the least metal to remove. Hex rod is the obvious pick for nuts, unions, nipples and anything that takes a spanner, because the flats are already there. Round rod suits pins, bushes, shafts, inserts and anything turned all over. Square rod is used for terminal blocks, connectors and parts that sit in a square pocket or are milled on four faces.

Order the across-flats size of hex rod to the finished spanner size where you can, so the flats do not need machining at all. Rods are typically sold in random lengths of around 3 metres; confirm length at enquiry if your bar feeder needs something specific.

Brass is about 8.5 g/cm³, a little denser than steel. With the size in millimetres, the weight per metre is:

• Round rod: 0.00668 × d² kg/m. A 25 mm round weighs about 4.17 kg/m.
• Hex rod: 0.00736 × AF² kg/m, where AF is the size across flats. A 22 mm hex weighs about 3.56 kg/m.
• Square rod: 0.0085 × a² kg/m, where a is the side. A 20 mm square weighs about 3.40 kg/m.

Lead helps machining but hurts other processes. Leaded brass does not cold head well, it can crack when riveted or swaged, and it is a poor base for brazing because the lead sweats out at temperature. For rivets, cold-headed pins, brazed assemblies and hot forgings, a lead-free 60/40 Muntz metal, 63/37 or 70/30 rod is the safer pick. Lead-free alpha brass rod also bends without cracking, which leaded rod does not do well.

Send the section, size, quantity in kilos or pieces, the grade or standard and whether you need extruded or commercial quality. We supply brass rod in Bangalore with a test certificate from a Government-recognised test house on a GST invoice. Machine shops making parts for the engineering and machining trade often ask us to quote hex and round together, which is fine. If you are moving a part from steel to brass, send the drawing and the machine type, and we can suggest a grade that suits your tooling and cycle time.