Materials

CNC machining materials for custom parts

Material selection affects machining time, part weight, corrosion resistance, strength, finish, price and lead time. The safest way to request a quote is to name the exact grade on the drawing or RFQ rather than writing only “steel,” “aluminium” or “stainless.” We review the material against the geometry and the required tolerance, then confirm the grade and documentation in the quote.

The material families below cover the common requirements for turned parts, milled parts, custom fasteners, housings, brackets, shafts and production components. A material certificate (MTR) is supplied with every order. If your program requires a particular standard, heat condition, hardness or additional certificate, include it with the drawing before pricing.

Stainless steel

Stainless options include 301, 303, 304 and 304L, 316 and 316L, 410, 416 and 17-4PH. 303 is commonly selected when machinability matters; 304, 304L, 316 and 316L are reviewed for corrosion-related requirements; 301 is used where the part has to take cold working or a spring temper; 410 and 416 are the hardenable grades, with 416 the free-machining variant; 17-4PH is considered when strength and heat treatment are part of the specification. Use the drawing to identify the exact grade, condition and finish. Related details are on the stainless steel parts page.

Aluminium

Aluminium options include 2024, 5052, 6061 and 7075. Aluminium is useful when low weight, machinability or anodized surfaces matter. 6061 is a common general-purpose choice, 5052 is the grade usually picked when formability and corrosion resistance matter more than strength, and 7075 and 2024 are reviewed when the drawing calls for a different strength or application requirement. Specify whether the part needs clear, black or another anodized finish, and identify any faces that must remain masked. See aluminum parts.

Carbon and alloy steel

Steel options include the carbon grades 1008/1018, 1045 and 1095, the free-cutting grades 1215 and 12L14, the alloy grades 4130 and 4140, and the tool steels D2 and O1. The right grade depends on strength, wear, thread performance, heat treatment and the environment around the part. A steel bracket, shaft, bolt or fixture may need a different route from a small turned component. State the grade, hardness or heat-treatment requirement on the drawing so the machining and finishing route can be quoted together. See steel parts.

Brass, copper and bronze

Brass and copper are used for fittings, adapters, electrical hardware, bushings and other parts where machinability, conductivity or corrosion behavior matters. Listed options include brass 260 and 360 (C360), copper 101 and 110 (C110), and bronze. Threads, thin walls and small bores should be shown clearly because they can affect tool selection and cycle time. See brass and copper parts.

Titanium

Titanium is available in Grade 2 (commercially pure) and Grade 5, also known as Ti-6Al-4V. Grade 2 is the softer, more formable option, used where corrosion resistance matters more than strength; Grade 5 is chosen for parts where the drawing requires its strength-to-weight and corrosion characteristics. Titanium needs a controlled machining approach because cutting conditions and tool wear affect cost and lead time. Send the full grade, quantity, tolerance and finish so the process can be reviewed from the drawing rather than estimated from the material name alone. See titanium parts.

Engineering plastics and elastomers

Not every part is metal. Acetal (POM), nylon (including PA 2200), polycarbonate, polyethylene (HDPE), polypropylene, acrylic, PTFE and FR4 glass-epoxy are all machined for parts where weight, electrical insulation, chemical resistance or a non-marring surface decides the choice — jigs and fixtures, insulators, spacers, wear pads, manifolds and prototypes. Acetal and nylon machine cleanly and hold a thread; PTFE is chosen for chemical and low-friction duties; FR4 is the usual answer for electrical hardware. Elastomers — NBR nitrile, neoprene and silicone — are supplied as machined parts, or as moulded parts where the geometry and the volume suit a tool; see injection molding.

Two things are worth stating up front on plastics. They move more with temperature than metals do, so give us the service temperature and say whether the tolerance has to hold at that temperature or only at room temperature. And the paperwork is different — there is no mill test report for a polymer, so tell us at the quote stage what your program actually requires and we will confirm what can be supplied with the batch.

How we buy material

We are not a material stockholder. Nothing on this page is sitting on a shelf waiting for an order — material is bought against your drawing, for your job, once the order is placed. That is worth knowing because it changes two things you might otherwise expect.

First, lead time. Production runs 25–35 days after sample approval, and that clock starts when the stock lands on our floor, not when you send the drawing. Common grades in common sizes move quickly through the Chinese supply chain and add nothing measurable. An unusual grade, a temper nobody keeps, a diameter outside the usual range or a plate thickness that has to be rolled to order can add days. We flag that in the quote rather than letting you discover it three weeks later.

Second, documentation. Material arrives with the mill’s test report for the heat it came from, and that report becomes the material certificate (MTR) that ships with your batch. The MTR is traceable to the heat, so the grade on the paper is the grade in the part. Read more on the material certificates page.

The buying route gives you access to both domestic Chinese mill material and imported stock, so a drawing that names an ASTM, EN, DIN or JIS grade is usually covered by one or the other. When the quote confirms your grade, that is the grade we buy. If a mill substitution ever became unavoidable, you would be asked in writing before anything was cut — we do not downgrade a material quietly.

If you would rather supply the material yourself, that works too. Free-issue stock is machined, the balance is returned or accounted for, and the MTR obligation stays with your supplier. Say so at the quote stage and we will price the machining separately from the material.

How to specify material in an RFQ

Include the material grade, condition or hardness when applicable, quantity, surface finish, critical tolerances and required documentation. Samples typically ship in 5-10 days and production in 25-35 days after drawing approval. Production orders start from 50 pieces per style and material, while prototype quantities are reviewed against the drawing.

For help choosing a process, compare CNC machining, CNC turning and CNC milling. To request pricing, send the drawing, material callout and quantity through the request a quote form.

What the grades look like as stock

The seven families below are the ones we hold or buy most often. The form matters as much as the grade: bar is bought by diameter for turned parts, plate by thickness for milled parts, and the same alloy in a different form quotes differently.

Grade reference table — the numbers behind the choice

Buyers usually arrive with a family in mind and a grade to confirm. This table is the confirmation: typical mechanical values at room temperature for the grades we machine most, plus the machinability rating that decides how the same geometry prices out in each one.

Grade	Family	Density (g/cm³)	Tensile (MPa)	Yield (MPa)	Melting (°C)	Machinability	Typical use
6061-T6	Aluminium	2.70	310	276	582–652	Very good	Housings, brackets, manifolds, general parts
7075-T6	Aluminium	2.81	572	503	477–635	Good	High-strength parts, aerospace fittings
2024-T4	Aluminium	2.78	469	324	502–638	Good	Fatigue-loaded aircraft parts
303	Stainless	7.90	620	240	1400–1450	Excellent (free-cutting)	Screws, shafts, bushings — the default stainless for turned parts
304 / 304L	Stainless	8.00	505	215	1400–1450	Fair (work-hardens)	Food, chemical, general corrosion resistance
316L	Stainless	8.00	485	170	1375–1400	Fair	Marine, medical, chloride environments
17-4 PH	Stainless	7.80	1000–1100 (H900)	850–1000	1400–1440	Fair	High-strength shafts, valve parts
H62 (CuZn38)	Brass	8.40	370	200	900–940	Excellent	Electrical, decorative, fittings
C110	Copper	8.94	220–250	70	1083	Good (gummy)	Conductors, heat sinks
1045	Carbon steel	7.85	585–620 (normalised)	310–350	1425–1540	Good	Shafts, gears, general mechanical parts
TC4 (Ti-6Al-4V)	Titanium	4.43	950	880	1604–1660	Poor (slow, tool wear)	Aerospace, medical implants, high strength-to-weight
Zamak 3	Zinc alloy	6.60	283	208	384–386	Excellent	Die-cast style parts, hardware, decorative

Three things to read out of the table, beyond the numbers.

Density decides the material bill, not the grade name. A 7075 part costs more than a 6061 part not only because the alloy is dearer but because the same block weighs 4% more. On a large housing that is a visible line.

Machinability decides the cycle time, which is the bigger line at volume. 303 stainless machines roughly twice as fast as 304 for the same feature, which is why free-cutting grades exist and why a switch from 304 to 303 can cut the piece price without changing the part.

Melting point matters for the process, not the part. It tells you whether a heat treatment or a coating can be applied afterwards without distorting the geometry — which is why the finishing choice is often made at the same time as the grade.

Values are typical published figures for the grade and condition shown; the certificate that ships with the order states the actual heat and the actual test result. Where a part needs a specific condition (H900, annealed, cold-drawn), say so on the drawing — the condition changes the numbers more than the alloy does.