Metal · Material guide
Custom steel parts from independent machine shops
Carbon and alloy steel are the strongest, stiffest, and lowest-cost-per-pound metals shops run. Upload a drawing and hear back from shops that machine 1018, 4140, A36, and tool steels every day.
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Carbon steel shops on OpenSpindle
Real shops that machine and fabricate carbon and alloy steel. See their equipment and talk to the person making your part.
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Grades
Steel grades shops run most
The grade sets strength, machinability, and whether the part can be hardened. These are the ones you will see quoted; if yours is not here, ask when you request a quote.
1018 cold rolled
The default low-carbon steel. Good machinability and weldability, a clean cold-drawn surface, and low cost. Not hardenable by heat treat, but case-hardens well for wear surfaces.
Best for Shafts, pins, spacers, brackets, and general parts
12L14
A leaded free-machining steel that cuts faster and cleaner than any other carbon grade. Low strength and poor weldability, so it is used where speed and finish matter more than load.
Best for Screw-machine parts, fittings, bushings, high-volume turned parts
1045
Medium-carbon steel with higher strength than 1018 and the carbon to through-harden or flame/induction harden. Machines and welds reasonably, a common step up when 1018 is not strong enough.
Best for Shafts, axles, gears, studs, and stressed parts
A36 hot rolled
The structural plate and bar standard. Low cost, welds easily, and readily available, but comes with mill scale and looser tolerances than cold-rolled stock.
Best for Weldments, frames, base plates, brackets, structural parts
4140 pre-hardened
A chromium-molybdenum alloy supplied pre-hardened to about 28-32 HRC with high strength and toughness. Machinable in the pre-hard condition, no heat treat needed for most parts, though preheat helps when welding.
Best for Shafts, gears, high-strength fixtures, tooling, mold bases
4130 chromoly
A weldable chromium-molybdenum alloy with a strong strength-to-weight ratio. Welds far better than 4140 and is common in tube and plate for frames and structures that see high load.
Best for Roll cages, aircraft and motorsport structure, welded assemblies
Tool steels (D2 / A2 / O1 / S7)
Hardenable high-carbon, high-alloy grades machined soft then heat treated to 55-62 HRC. D2 and A2 hold an edge for cutting and forming, O1 is easy to harden for one-offs, and S7 resists shock.
Best for Dies, punches, cutting and forming tools, wear parts
Specs
Material properties
Representative values for 1018 cold rolled, the most common machining grade. Exact numbers vary by grade and heat treat.
| Property | Typical value |
|---|---|
| Density | 7.87 g/cm³ (0.284 lb/in³) |
| Tensile strength (1018 CR) | ~64 ksi (440 MPa) |
| Yield strength (1018 CR) | ~54 ksi (370 MPa) |
| Hardness (1018 CR) | ~126 HB |
| Hardness (4140 pre-hard) | ~28-32 HRC |
| Machinability | Good; 12L14 excellent (free-machining benchmark ~160%) |
| Corrosion resistance | Poor. Rusts; must be coated or oiled |
| Weldability | 1018/A36/4130 good; 4140 and up need preheat |
Steel is roughly three times the weight of aluminum and cuts slower, but delivers the highest strength and stiffness per dollar, which is why it dominates structural, high-load, and tooling parts.
Stock
Forms we machine it from
Plate & block
Milled and machined parts, weldment plate, and mold bases from solid.
Round bar
Turned shafts, pins, axles, and cylindrical parts.
Sheet
Laser, plasma, and press-brake sheet metal and weldments.
Processes
Manufacturing methods for carbon steel
The right process depends on part geometry, tolerances, and production volume.
Finishing
Finishes for carbon steel
Steel rusts, so nearly every part gets a finish, plating, or oil. The right one depends on the environment and whether the surface is cosmetic.
Black oxide
A thin conversion coating that turns the surface black and adds mild corrosion resistance. Dimensionally negligible, so it is common on toleranced parts, followed by oil for real protection.
Zinc plating
An electroplated sacrificial layer, clear or yellow, that protects steel in indoor and mild outdoor use. The go-to low-cost corrosion finish for hardware and brackets.
Nickel plating
A harder, brighter plated layer with better corrosion and wear resistance than zinc. Used where appearance and durability both matter.
Powder coat
Durable colored coating over a broad range of textures. Thicker than plating, so mask threads and mating faces and account for the added thickness.
Bluing
A controlled black oxide finish traditional on firearms and tooling. Cosmetic and mildly protective, and needs oil to prevent rust.
Oil / rust-preventive
A light oil or wax film that ships with bare or black-oxide parts. The minimum protection; bare steel begins to rust within hours of machining without it.
As-machined
No finish. Only for internal or short-lived parts, and it must be oiled immediately or it will rust.
Unlike aluminum or stainless, carbon steel has no natural corrosion protection. Specify a coating or oil with your drawing, or the part will rust before it reaches you.
Applications
Where carbon steel parts are used
Steel shows up wherever strength, stiffness, hardness, or cost matter more than weight or corrosion resistance.
Compare
Carbon Steel vs other materials
How carbon steel stacks up against the other metals shops quote most.
Carbon Steel vs Aluminum
Aluminum →- Steel is stronger and stiffer for the same volume, and costs less per pound
- Aluminum is about one-third the weight and machines several times faster
- Aluminum does not rust; steel must be coated or oiled to survive
Choose carbon steel for maximum strength, stiffness, and hardness at low cost. Choose aluminum for light, fast, corrosion-free parts.
Carbon Steel vs Stainless steel
Stainless steel →- Stainless resists corrosion with no coating; carbon steel rusts without a finish
- Carbon steel is cheaper, machines more easily, and can hit higher hardness in tool grades
- Stainless holds up better in food, medical, marine, and chemical environments
Choose carbon steel for strength and cost when the part is coated or lives indoors. Choose stainless when corrosion resistance or hygiene is required.
Carbon Steel vs Titanium
Titanium →- Titanium has a far better strength-to-weight ratio and does not corrode
- Carbon steel is several times cheaper, easier to machine, and stiffer for the same volume
- Titanium is biocompatible and handles heat and chemicals carbon steel cannot
Choose carbon steel for cost, stiffness, and hardness. Choose titanium when strength-to-weight, corrosion, or biocompatibility justify the premium.
Questions
Frequently asked questions
Carbon steels like 1018, 1045, and A36 get their properties mainly from carbon content and are the low-cost workhorses. Alloy steels like 4140 and 4130 add elements such as chromium and molybdenum for higher strength, toughness, and hardenability. Use carbon grades for general parts and alloy grades when you need more strength or the ability to heat treat.
Get carbon steel part quotes
Upload a drawing once and compare quotes from independent shops that machine, cut, and finish carbon and alloy steel.
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