Brass 260 (Cartridge Brass) CNC Machining

The other end of the brass family

Copper alloys divide cleanly into two groups, and brass 260 and brass 360 are the clearest example of the split.

	Brass 260	Brass 360
Copper	~68.5–71.5%	~60–63%
Lead	None	~2.5–3.7%
Bought for	Formability	Machinability
Deep drawing	Excellent — the reference grade	Not its purpose
Machining	Poor — gummy and stringy	100% on the scale
Corrosion resistance	Better, from the higher copper	Moderate
Lead restrictions	Not an issue	Governed by the copper-alloy exemption

260 is a single-phase alpha brass — all of the zinc is in solid solution, which is what makes it so ductile and so good to form. 360 carries enough zinc to form a second phase, plus lead, which is what makes it cut. The two grades are not interchangeable in either direction, and choosing between them is usually decided by one of two questions: is the part cut or formed, and can it contain lead.

Why 260 is the lead-free answer

Given what brass 360 involves, this is the more commercially useful half of the page.

Brass 360 relies on an exemption — copper alloy containing up to 4% lead by weight — to be used in electrical and electronic equipment, and it is generally not acceptable for wetted potable-water contact at all. Where either of those applies, a part that has to be brass needs a brass with no lead in it.

Brass 260 has no lead. That makes it the grade to specify when:

• The application touches drinking water, where lead limits are far stricter than the electronics exemption
• The market or the customer restricts lead independently of any exemption
• The part is a food-contact or medical component where lead is unwanted on principle as well as by rule
• A declaration has to be made without reference to an exemption, because the exemption does not apply to the product category

The trade is entirely at the machine. Brass 260 with no lead is gummy and stringy, producing long chips, built-up edge and a finish that will not match what 360 delivers on the same operation. On a small part produced in volume, that difference in cycle time is the price of removing the lead, and it is a real price — not a formality.

The way to think about it is straightforward: 360 is the cheap part that may be hard to sell; 260 is the more expensive part that is easy to sell. Where lead is not an issue, 360 wins on cost every time. Where it is, 260 is the answer and the machining penalty is simply part of the quotation.

Higher copper buys more than a colour

The other consequence of 260’s composition is worth naming because it shows up in the parts.

At roughly 69% copper against 60–63% in 360, cartridge brass offers:

• Better corrosion resistance, because copper is the corrosion-resistant component of the alloy and there is more of it
• A deeper, warmer colour, which matters on visible architectural hardware, instrument bezels and fittings where the brass is polished and lacquered rather than plated
• Better electrical conductivity in relative terms, though both grades land around 28% IACS and neither is a conductor on the scale of pure copper

Where a part will be left bare and polished rather than plated, the colour difference is visible, and it is a legitimate reason to choose 260 over 360 on decorative work.

Machining brass 260

This is not a free-machining material, and it should not be quoted as one.

The problems are the familiar ones from low-carbon steel, and the answers are the same:

• The chip does not break. Long stringy chips tangle the tool and the workpiece, interrupt the cut and scratch the finished surface on a finishing pass.
• The edge builds up. Soft, ductile brass tends to weld to the cutting edge, particularly at conservative speeds. The built-up material rounds the edge geometry, degrades the finish and eventually breaks away, sometimes taking part of the edge with it.
• The finish is duller than 360 produces on the same operation, and a part specified to a fine finish may need a second operation that 360 would not.

What works:

• Sharp, positive-geometry tooling with a chipbreaker suited to the depth of cut — on a grade with no free-machining addition, tool geometry does most of the work
• Adequate feed per tooth, so the edge shears under the deformed layer instead of burnishing over it
• Higher speeds than instinct suggests. Brass conducts heat well and the cut runs cool; running too slowly is what lets built-up edge take hold
• Rigid workholding, particularly where the part is thin-walled or supplied in a tempered condition

Two application-specific cautions.

Tempered stock cuts and behaves differently. Where the part is supplied in half-hard, three-quarter-hard or spring temper, the material is stronger, springier and harder on tooling, and residual stresses release as material is removed — so a thin part can move after the cut. Where machined features exist on a tempered part, saying so at the enquiry lets the sequence be planned.

Fine threads and thin walls deform. Brass is soft, and a very fine thread or a thin section can be damaged by the tooling or by clamping pressure even though it cuts cleanly.

Precision features are held to ±0.01 mm with ISO 2768-m as the general tolerance block — see tolerances we hold.

Corrosion behaviour

Brass 260 performs better than free-cutting brass in most environments, and it is still not immune to the two failure modes that affect the brass family.

Stress-corrosion cracking in ammonia. Brasses crack under sustained tensile stress when ammonia or amines are present. Cold-worked parts destined for that kind of service are stress relieved, and where a part will see ammonia — cleaning agents, refrigeration systems, certain process fluids — it should be flagged at the enquiry rather than quoted silently.

Dezincification. In some waters, particularly stagnant or aggressive ones, zinc is leached selectively out of the alloy, leaving a porous copper-rich residue that looks intact and fails structurally. The higher copper content of 260 makes it somewhat less prone to this than 360, but it does not make it immune.

Neither of these is a reason to avoid the grade. Both are reasons to say what the part touches.

Where brass 260 is the right choice

• Any brass part that must be lead-free — the primary reason the grade appears on a machined drawing
• Potable-water fittings and components, where leaded brass is generally not acceptable
• Food-contact and medical hardware in brass
• Visible architectural and instrument hardware left bare and polished, where the deeper colour matters
• Deep-drawn parts — cartridge cases, eyelets, housings, radiator cores
• Rivets, hardware and small fittings where the part is formed or headed rather than turned
• Spring components made from strip in the harder tempers
• Machined details that sit alongside formed 260 parts and share the material call-out

Where brass 260 is the wrong choice

The part is turned or milled in volume and lead is acceptable. Brass 360 cuts several times faster and finishes better. Choosing 260 there is paying a machining penalty for a restriction that does not apply.

The requirement is spring behaviour in a machined part. Machining a spring element from tempered stock is expensive and the result is usually worse than a formed strip part. Form it instead.

High-conductivity electrical duty. At around 28% IACS, brass is about a quarter as conductive as pure copper. Where the current path is long or the section limited, the grade is copper 110 or copper 101.

Heavy-load bearings. Where a bushing carries real load, the bearing bronzes exist for that duty — see bronze.

A welded assembly. Brasses are not fusion-weldable in practice. Design for a braze or a solder joint, or reconsider the material.

A part that must stay bright without a coating. Bare brass tarnishes, and 260 is no exception. If it has to stay bright, it needs a lacquer or a plating, and that should be specified.

Finishing brass 260

• Polishing and brushing — the grade takes a deep reflective or directional finish, and on decorative work this is often the whole specification
• Lacquering — the standard way to hold a bright brass finish, since bare brass darkens in air
• Nickel plating — a hard bright barrier for hardware and electrical parts
• Chrome plating — a hard decorative finish, normally over a nickel layer
• Tumbling and deburring — the standard route for small parts, and often the only operation needed

One point worth planning: where a part is both close-tolerance and plated, the coating thickness has to be built into the machined dimension rather than added on top of it. Saying at the enquiry that the part will be plated is enough for that to be handled in the route.

All finishing runs through our vetted partner network, managed under one quality process. The grades we run across every process are listed on the materials page.

What to put on the drawing

Instead of	Write
Brass	Brass 260, if the part must be lead-free or is formed rather than cut
Brass 260, turned part in volume	Expect a machining penalty — brass 360 cuts far faster if lead is acceptable
Brass 260, potable water	Correct — this is the lead-free choice
Brass 260, temper	State it — annealed and spring temper machine and behave very differently
Brass 260, will be welded	Not a welding grade — design for a braze or a solder joint
Brass 260, must stay bright	State the finish — bare brass tarnishes
Brass 260, ammonia service	Flag it — stress-corrosion cracking risk
Brass 260, high-current conductor	Wrong grade at ~28% IACS — use copper 110 or 101

The two lines that decide most brass 260 specifications are whether lead is restricted and whether the part is cut or formed. The first is what puts 260 ahead of 360. The second decides whether either grade is right, or whether the part belongs in a different family entirely.

Material is bought against your drawing for your job, and every batch ships with a material certificate (MTR) tracing the grade and temper to its mill heat plus pre-shipment photos of the actual parts. Orders start at 50 pieces per style and material, samples from a single piece in 5–10 days, and production runs in 25–35 days after sample approval. Send the drawing through the request a quote form and the reply comes back within 24 hours with DFM feedback — including a note on the temper and the finish where either applies.