Crafted in 3D | Machining Material Selector

Machining Material Selector

What the part has to do

Set the requirements. The list narrows to materials that qualify, and the sort follows your priority.

Priority

Sets the sort order. Click any column heading to override.

Environment Outdoors / weather Marine / saltwater Harsh chemicals

Must be non-magnetic Needs to be welded

Planned finish

Max cost tier

$$$$$

Material families

0 of 0 materials qualify

We cut every grade listed here, and we supply the mill test report when you ask for it.

Select a material's name for what it is good for, why you would pick it, and what to watch. Click a column's i for what it means.

Figures are typical published values for wrought stock (supplier and MatWeb data). Real properties shift with temper, heat treatment, section size, and direction, and machined plastic stock is affected by the residual stress in the bar. Nothing here is a spec: the material and grade for your part are confirmed on the quote. We machine the grade you specify. We do not certify parts for food contact, medical, implant or aerospace use. Strength and stiffness are the same numbers whichever units you view; only the display converts.

What each column means, in plain shop terms, and how to read it when you are choosing a material for a part rather than figuring out how to cut it. Tap any row to open it. Every value is a typical published range for standard stock; the real part depends on the grade, the heat treat, and how it is loaded.

Choosing a material

The family is the first cut and it decides most of what follows. Aluminum is light, cheap, corrosion-resistant bare, and takes anodizing, so it is the default for brackets, housings, and anything cosmetic. Carbon and alloy steel is strong and stiff for the money but rusts, so it wants paint, plating, or oil. Stainless trades some strength and a lot of cost for not needing a coating. Brass and bronze machine like butter and are the answer for bearings, bushings, fittings, and electrical work. Plastics are for light weight, electrical isolation, chemical exposure, low friction, or clarity, not for strength. Composites like G10 and carbon plate are stiff, light, and inert, but awkward to fasten.

Pick the family from the job, then use the columns to pick the grade within it.

A rough band for the raw material only. It is not the price of the finished part, which also carries machining time and finishing. But the stock band is a good early filter: mild steel and 6061 sit at $, most stainless and tool steels at $$ to $$$, and the high-performance plastics like PEEK and Ultem run to $$$$ and $$$$$ per pound even before a chip is cut.

When two materials both do the job, the cheaper one usually wins on the delivered price too. The step-down note in each material's detail points at the cheaper option when the top grade is more than the part needs.

Strength and stiffness

Yield is the number that matters for a working part. Below it the metal springs back; past it the metal takes a permanent set and your part is bent, even though it has not broken. Design load should stay well under yield, with a safety margin.

Landmarks: 6061-T6 yields around 275 MPa, mild steel around 350, 4140 pre-hard around 700 to 850, and 17-4 stainless past 1100. Plastics are an order of magnitude lower, roughly 40 to 100 MPa. On the curve it is the point where the line stops being straight.

The peak of the curve: the most pull the material carries before it fractures. It sits above yield, and the gap between the two tells you how much warning you get. A wide gap (mild steel, 304 stainless, most aluminum) means the part stretches and necks visibly before it lets go. A narrow gap (hardened tool steel, cast bronze, acrylic) means it goes from fine to failed with little between.

Use tensile for a sense of ultimate capacity and for comparing materials, but size real parts to yield, not tensile.

Stiffness (elastic modulus) is the slope of the straight part of the curve: how far the part deflects before anything permanent happens. It is set by the family and barely moves with grade or heat treat. All steels and stainless are about 200 GPa. All aluminum alloys are about 69 GPa, one third of steel. Titanium is in the middle; brass, bronze and copper run 97 to 117 GPa, about half of steel and well above aluminum; plastics run 0.4 to 4 GPa, a fiftieth of steel or less.

If your part is flexing when it should not, a stronger alloy in the same family will not help. You need a stiffer family, a thicker section, or a better shape (a rib, a box, a larger radius). Heat-treating 6061 to a higher temper raises its strength and does nothing for its stiffness.

The percent the test bar stretches before it breaks. High numbers (20% and up: mild steel, 304, annealed copper, nylon) mean a ductile material that bends, dents, and absorbs a knock. Low numbers (a few percent: hardened tool steel, cast iron, acrylic, G10) mean a brittle material that chips or cracks instead of bending.

It matters when the part sees impact, vibration, or the chance of a shock load, and when you want a bent part rather than a shattered one as the failure mode.

Straight weight. Steel and stainless are about 7.8 g/cm³ (0.28 lb/in³). Aluminum is 2.7, about a third. Brass, bearing bronze and copper are heavier than steel at 8.5 to 8.9; aluminum bronze is a little lighter at about 7.5. Titanium is 4.5. Machinable plastics run 0.9 to 1.4, and PTFE is dense for a plastic at 2.2.

For a part where weight is a real constraint (anything that moves, flies, or gets carried), aluminum, plastic, or composite is the move. For a part that wants mass on purpose (a base, a flywheel, a counterweight), lean into steel or bronze.

Hardness and wear

Hardness is how well a surface resists being pushed in, and it stands in for wear life, scratch resistance, and thread durability. Two scales show up: Brinell (HB) for soft and medium metals and Rockwell C (HRC) once a steel is hardened, where roughly 30 HRC is 285 HB and 60 HRC is around 650 HB. Plastics use Rockwell R or Shore D and are all soft by comparison.

If the part is a wear surface, a slide, a gear tooth, a pivot, or a thread that gets taken apart often, favor a harder material or a hardenable one (4140, 17-4, 440C, tool steels, hard-anodized aluminum). If it just needs to hold a shape, medium hardness is plenty and it will cost less.

Environment

The rating is how the bare material does with no coating. Poor means it rusts and needs paint, plating, or oil (all carbon and alloy steel). Fair is indoor-dry only or needs a finish outdoors. Good handles weather and humidity. Very good handles occasional salt and washdown. Excellent handles marine service, chemicals, and constant wet (316 stainless, most plastics). 316 has a limit: one stainless supplier says it is not resistant to warm sea water.

Two extra rules. Anodizing an aluminum part moves it up a band. And mixing metals matters: bolt a steel fastener into an aluminum part in a wet environment and the aluminum corrodes away to protect the steel. Keep dissimilar metals apart, or isolate them, or match to stainless.

Matters more often than people expect: near sensors and hall effects, in lab equipment, around compasses, on magnetic work-holding, and anywhere stray fields are a problem. Non-magnetic: all aluminum, brass, bronze, copper, plastics, and the austenitic stainless grades (303, 304, 316) in the annealed state, though heavy machining can make 303 and 304 slightly magnetic at the cut surface. Magnetic: all carbon and alloy steel, and the hardenable stainless grades (410, 416, 440C, 17-4, 15-5).

If the part must be truly non-magnetic and also strong and corrosion-resistant, 316 stainless or aluminum bronze are the usual answers.

Finishing the part

We machine the part. Anodizing, plating and coating are not done in house, so name the finish on your quote request.

Not every finish works on every metal, so decide the finish before the material. The common ones:

Anodize (aluminum only): grows a hard oxide skin that can be dyed almost any color. Standard (Type II) is the cosmetic one; hard-anodize (Type III) is thicker and much harder, for wear surfaces, and comes out dark gray or black. 6061 and 6063 anodize clear with good protection (6063 is the anodizing-quality grade), and 5052 takes a clear protective coat too. 7075 can come out with a brown tint, 2024 anodizes yellowish with weaker protection, and cast plate looks mottled.

Plating (steel, stainless, brass): zinc or zinc-nickel for cheap rust protection, electroless nickel for an even hard corrosion layer over any shape, hard chrome for wear. Steel almost always wants one of these or paint.

Powder coat or paint: works on any metal, adds color and a rust barrier, but adds a few thousandths to every surface, so mask threads and bearing fits.

Passivation (stainless): a mild acid dip that cleans iron off the surface and restores full corrosion resistance after machining. Cheap, invisible, and worth doing on any stainless part that has been cut.

Bead blast, tumble, brush: texture and uniformity, no protection. Often the finish on a stainless or anodized-then-blasted part.

Only relevant if the design joins pieces by welding rather than fasteners. Good: mild steel, 5052 and 6061 aluminum, 304L and 316L stainless. Fair: medium-carbon and alloy steels (1045, 4140) that need preheat and post-heat, and standard 304/316 that can sensitize. Poor or not recommended: free-machining grades (12L14, 303, C360 brass) whose lead and sulfur crack the weld, the high-strength aluminum alloys (2024, 7075), and most cast and hardened materials.

Note that welding a heat-treated aluminum part throws away the temper in a band around the weld: a welded 6061-T6 bracket is only as strong as annealed 6061 near the joint unless it is re-heat-treated.