Materials for Micro Machining: Stainless, Titanium, Brass, PEEK and More

By the Micropartz editorial team · Published October 28, 2026

A micro part often weighs less than a gram, so material cost barely registers on the quote. Yet material choice decides how small a feature can be, how tight a tolerance is realistic, how much deburring is needed and how many tools break. This guide compares the metals and plastics most often used for micro machined parts and shows what each one means for tolerance and cost. For the process side, see the guide to feature sizes and tolerances in micro milling and turning.

Why material matters more at micro scale

Three properties dominate once features fall below 1 mm.

• Chip formation. Materials that break chips cleanly, like free-cutting brass or 303 stainless, let small tools cut freely. Gummy materials, like 316L or pure copper, wrap chips around the tool and smear.
• Burr formation. Ductile materials push metal ahead of the tool and leave burrs at every exit. On a 0.3 mm cross hole, a 20 μm burr can block the hole.
• Stiffness and stability. Metals hold their shape under clamping and cutting forces. Plastics deflect, creep and change size with temperature and moisture.

That is why the same drawing can be routine in brass and difficult in titanium.

Metals for micro machining

Material	Common grades	Micro machinability	Burrs	Typical tolerance on selected features	Typical uses
Free-cutting brass	C36000 (CuZn36Pb3)	Excellent	Low	±0.005 mm	Connectors, watch parts, instrument pins
Copper	C11000, C10100	Poor, gummy	High	±0.01 mm	Electrodes, RF parts, heat spreaders
Stainless, free machining	303	Good	Moderate	±0.005 mm	Pins, fittings, general parts
Stainless, austenitic	304, 316, 316L	Fair	High	±0.005 to ±0.01 mm	Medical, food, fluidic parts
Titanium	Grade 2, Grade 5 (Ti-6Al-4V)	Fair, heat and wear	Moderate	±0.005 to ±0.01 mm	Implants, dental, aerospace
Aluminum	6061-T6, 7075-T6	Good	Moderate to high	±0.005 mm	Semiconductor and optics housings
Tool steel	D2, H13, SKD11	Fair annealed, hard when hardened	Low	±0.005 mm, grinding for tighter	Mold inserts, punches, wear parts

Ratings and tolerances are typical shop experience for small parts, not specifications.

Brass and copper

Brass C36000 is the reference point for machinability. It is the material to choose if function allows, because every other metal is compared to it. Copper is the opposite. Pure copper is soft and gummy, loads the tool and burrs heavily. Where conductivity allows, tellurium copper (C14500) machines much better.

Stainless steels

303 contains sulfur, which forms inclusions that break chips. It is the easiest stainless to micro machine but has lower corrosion resistance and is usually not accepted for implants. 316L is the standard for medical parts, often to ASTM F138 for implants. It is tougher on tools and needs careful deburring. 17-4 PH is used where strength matters and machines reasonably in the H900 or H1025 condition.

Titanium

Ti-6Al-4V, also called Grade 5, is the common choice for implants and high-strength small parts, with the ELI variant to ASTM F136 for implant grade. Titanium conducts heat poorly, so heat stays at the cutting edge and wears small tools quickly. Shops run lower cutting speeds and change tools more often, which shows up in cycle time. Grade 2, commercially pure titanium, is softer and gummier and burrs more.

Aluminum

6061-T6 and 7075-T6 cut fast and hold size well, which makes aluminum popular for semiconductor, optical and electronics housings. The main issue at micro scale is burrs on thin edges and softness when handling finished parts. Anodizing adds a few microns per surface, so tight features need allowance on the drawing.

Tool steels

D2, H13 and SKD11 are machined annealed and then hardened, or machined hard with special tooling. Hardening can distort thin micro features. For the tightest tolerances on hardened parts, shops finish by grinding, wire EDM or hard milling.

Plastics for micro machining

Plastic	Stability	Typical tolerance on small features	Notes
PEEK	Best of the group	±0.01 mm, ±0.005 mm selected	Biocompatible grades, high temperature, annealed stock preferred
POM (acetal, Delrin)	Good	±0.01 to ±0.02 mm	Machines cleanly, low friction
PTFE	Poor, creeps	±0.02 to ±0.05 mm	Soft, moves under clamping and temperature
PEI (Ultem)	Good	±0.01 mm	Stiff, amorphous, good for insulators
PMMA	Fair	±0.02 mm	Optical parts, prone to cracking on small features

Typical values for small parts, not a guarantee.

Plastics expand far more with temperature than metals, roughly 5 to 10 times as much as steel. A PTFE part measured at 25 °C may be out of tolerance at 20 °C. Plastics also relax after machining as internal stresses release. Good practice is to use annealed stock, machine in stages and measure after the part has settled.

Less common materials

Some micro parts call for materials outside the usual list. These are machinable at small scale, but fewer shops have experience with them, so they narrow the choice of supplier.

• Nitinol (nickel titanium). Used for medical devices because of its superelasticity and shape memory. It work hardens quickly, wears tools fast and is often cut by laser or wire EDM rather than milled. Heat input can change its transformation temperature, so shops need to control it.
• Precious metals. Gold, platinum and platinum-iridium alloys appear in medical electrodes, connectors and watch parts. They are soft and gummy, and the material cost becomes significant. Shops usually account for chips and remnants separately, because they have scrap value.
• Tungsten and tungsten alloys. Dense and hard, used for radiation shielding, weights and electrodes. Machinable with carbide tools at low speeds, and often finished by grinding or EDM.
• Beryllium copper. Used for springs and contacts. Machines well, but dust and chips are a health hazard, so only shops with the right controls handle it.
• Ceramics and glass. Alumina, zirconia and fused silica are not usually cut like metal. They are ground, lapped, laser machined or machined in the green state before sintering. Treat them as a different supply chain from micro CNC machining.

Material	Typical process	Supplier pool
Nitinol	Laser cutting, wire EDM, careful milling	Specialist
Platinum-iridium, gold	Swiss-type turning, micro milling	Specialist, material handling rules
Tungsten alloys	Turning and milling at low speed, grinding	Moderate
Beryllium copper	Swiss-type turning, milling with dust control	Limited by safety requirements
Alumina, zirconia	Grinding, green machining, laser	Separate ceramic suppliers

Typical practice for orientation.

If your part uses one of these materials, say so in the first line of the RFQ. It removes most of the shops that would otherwise quote and then decline.

Matching material to tolerance and cost

A useful way to think about material is a combined factor for cycle time, tool wear and deburring effort.

Material	Relative machining effort (brass = 1.0)
Brass C36000	1.0
Aluminum 6061	1.1 to 1.3
Stainless 303	1.5 to 2
POM	1.2 to 1.5
PEEK	1.5 to 2
Stainless 316L	2 to 3
Titanium Grade 5	2.5 to 4
Hardened tool steel	3 to 5

Illustrative ratios for small parts, not a price list. Actual cost depends on geometry, tolerances and quantity.

Hypothetical example: a sensor pin was designed in 316L out of habit. The function only needs moderate corrosion resistance and no body contact. Switching to 303 lowers machining effort and burr removal noticeably, while keeping diameters at ±0.005 mm. For an implant, the same switch is not allowed, and the extra cost of 316L to ASTM F138 is simply part of the product.

See also: the micro machining materials matrix compares burr tendency, grain size effect and tool life for each material on one page.

How to specify material in an RFQ

1. Grade and standard. “Ti-6Al-4V ELI to ASTM F136”, not “titanium”.
2. Condition. Annealed, T6, H900, hardened to a stated HRC after machining.
3. Form. Ground bar, drawn bar, plate or rod, plus any required diameter tolerance for Swiss-type work.
4. Certificates. Mill certificate traceable to the heat or lot, often required for medical and aerospace.
5. Approved sources. If your quality system requires a specific mill or distributor, say so up front.
6. Finishing. Passivation, anodizing, electropolishing or coating, with thickness allowances.

The micro machining buyer’s guide explains how material fits into the rest of a complete RFQ, and the guide to measuring micro parts covers why plastics need extra care at inspection.

Next step

Typical grades and tolerances are summarized on the tolerance and materials reference. When you know the material and the tightest tolerance, send an RFQ. Micropartz matches it with up to 3 shops that already machine that material at micro scale and replies within 24 business hours.

Frequently asked questions

Reviewed against

• ASTM F138, Wrought 18Cr-14Ni-2.5Mo Stainless Steel Bar and Wire for Surgical Implants (UNS S31673)
• ASTM F136, Wrought Titanium-6Aluminum-4Vanadium ELI Alloy for Surgical Implant Applications
• ASTM B16, Free-Cutting Brass Rod, Bar and Shapes for Use in Screw Machines
• Wikipedia: Ti-6Al-4V

Numbers in this guide are typical values for orientation. The drawing, the material certificate and the matched shop set the real ones.

Keep reading

• Micro Machining: A Buyer's Guide to Very Small Precision Parts
• Minimum Feature Sizes, Tools and Tolerances in Micro Milling and Turning
• What Micro Machined Parts Cost and Why Inspection Is Half of It