What is the best material for CNC machining prototypes?

6061-T6 aluminum is the most cost-effective choice for prototypes. It machines fast, holds detail well, and is easy to modify. For functional plastic prototypes, Delrin/Acetal is a solid choice.

What material is strongest for CNC machining?

Inconel 718 offers the highest strength at 1,350 MPa tensile, but it's expensive and difficult to machine. 17-4PH stainless at 1,100 MPa is a more practical choice for most high-strength applications at lower cost.

Which stainless steel is easiest to machine?

303 stainless is the most machinable — it's specifically designed for free machining. 304 and 316 are harder on tooling and more prone to work-hardening.

CNC Material Selection Guide

12 common engineering materials compared: machinability, strength, cost, corrosion resistance, and applications.

Written by Wei Zhang, Lead CNC Programmer — 15 years CAMReviewed by Xiaofeng Li, Quality Manager — July 2026

I've machined thousands of parts in 40+ different metals and plastics over 18 years. Material selection is where most project mistakes happen — picking the wrong grade costs far more than the material itself when you account for tool wear, cycle time, and scrap.

Here's what I tell every customer who asks "what material should I use?"

Engineering Alloy Matrix

Material	Machinability	Tensile Strength	Corrosion	Cost	Best Applications
6061-T6 Aluminum	Excellent	310 MPa	Good	$	Prototypes, structural, aerospace brackets, automotive
7075-T7351 Aluminum	Good	570 MPa	Good	$$	High-stress aerospace, missile components, gears
303 Stainless	Excellent	690 MPa	Good	$$	Fittings, fasteners, shafts, connectors
304 Stainless	Good	760 MPa	Excellent	$$	Food equipment, medical devices, enclosures
316 Stainless	Fair	620 MPa	Excellent	$$$	Marine, pharmaceutical, chemical equipment
17-4PH Stainless	Good (annealed)	1,100 MPa	Excellent	$$$	Aerospace shafts, valve components, surgical tools
Ti 6Al-4V Grade 5	Fair	950 MPa	Excellent	$$$$	Aerospace structural, medical implants, motorsport
Inconel 718	Challenging	1,350 MPa	Excellent	$$$$$	Turbine blades, exhaust, oil & gas downhole
Brass C360	Excellent	400 MPa	Good	$$	Fittings, valves, electrical components, decorative
Copper C110	Good	350 MPa	Good	$$$	Electrical bus bars, heat sinks, welding tips
PEEK	Good	100 MPa	Excellent	$$$$	Medical implants, aerospace, semiconductor, bearings
Acetal / Delrin	Excellent	70 MPa	Excellent	$$	Bushings, gears, jigs, food-grade parts

See detailed guides: Aluminum · Stainless · Titanium · Inconel · PEEK

Need help selecting material?

Tell us your application requirements — strength, environment, weight, cost targets. We'll recommend the optimal material.

Ask Our Engineers →

Start with the environment, not the catalogue

Corrosion, temperature, load, weight budget — in that order. 6061-T6 aluminium handles most indoor structural work at a third the weight of steel. The moment the part sees salt, chemicals or body fluid, 304 or 316 stainless enters the picture. Above 200°C, aluminium is out and the question becomes which steel or superalloy.

The second question is what the part mates with. Dissimilar-metal corrosion between aluminium and stainless is a real failure mode in outdoor assemblies. A small plastic isolator or anodized interface solves it; ignoring it means the part corrodes exactly where it touches its neighbour.

What the shop needs to know before quoting

Send the grade, not the family. Aluminium is not a material specification — 6061-T6 and 7075-T6 machine differently, cost differently and have different strength and corrosion profiles. The same applies to stainless: 304L and 17-4PH are different worlds for machining and heat treatment.

If the part needs a coating, say so at RFQ stage — anodize tolerance, plating thickness and passivation all affect dimensions and fit. And if you are choosing between two materials, tell us the function; we will often tell you which one machines cleaner for the same result, and which one will cost you a delivery date.