What type of steel is 4140? Is it stainless or a tool steel?

4140 is a chromium-molybdenum alloy steel, AISI/SAE 4140 (UNS G41400), with 0.38–0.43% carbon, 0.80–1.10% chromium and 0.15–0.25% molybdenum. It is not stainless, it is not a tool steel, and it is magnetic. It has high strength and toughness and through hardens.

Is 4140 steel easy to machine?

Annealed 4140 machines well, with an AISI machinability rating of about 66%. Pre-hardened 4140 (28–32 HRC) also machines well with carbide tooling and coolant, at lower cutting speeds. We CNC turn and mill both.

What is 4140 prehard?

It is 4140 supplied already quenched and tempered, at about 28–32 HRC. It is machined directly and the part is finished at that hardness, with no heat treat step and no risk of heat treat distortion.

What is the hardness of 4140 steel?

Annealed or normalized 4140 is about 197–241 HB (Brinell). Prehard is about 28–32 HRC. Quenched and tempered to order it can be harder, and nitriding gives a surface much harder than the core.

Is 4140 steel weldable?

Yes, with preheat, slow cooling and, on critical parts, stress relieving afterwards. Without that control it can crack near the weld.

How much do custom 4140 steel parts cost?

It depends on size, geometry, annealed or prehard stock, finish and quantity. As a reference, a 4140 steel stepped shaft of Ø25 × 150 mm with a keyway costs $80.84 USD for 1 part, $19.39 each at 25 and $17.02 at 100. Upload your file to get the exact price of your part instantly.

Do you machine custom 4140 steel parts from a single piece?

Yes. Upload your CAD file (STEP) and get an instant price and delivery date, from one part to production.

CNC turning and milling · From 1 part

4140 Steel
CNC Machining

4140 steel shafts, axles, spindles, mold pins and tooling, annealed or pre-hardened, turned and milled from your file. Upload your CAD and order online, starting at a single part.

See 4140 properties

Stepped shaft

4140 Steel · Ø25 × 150 mm · With keyway

1 pc

$80.84 USD

per part

25 pcs

$19.39 USD

per part

-76.01%

100 pcs

$17.02 USD

per part

-78.95%

Loading…

Manufacturing services

CNC turning and milling · From 1 part

4140 Steel
CNC Machining

4140 steel shafts, axles, spindles, mold pins and tooling, annealed or pre-hardened, turned and milled from your file. Upload your CAD and order online, starting at a single part.

See 4140 properties

Stepped shaft

4140 Steel · Ø25 × 150 mm · With keyway

1 pc

$80.84 USD

per part

25 pcs

$19.39 USD

per part

-76.01%

100 pcs

$17.02 USD

per part

-78.95%

Material Overview

What is Steel 4140?

4140 is a chromium-molybdenum (Cr-Mo) alloy steel with high strength, toughness and good fatigue resistance. It comes annealed, to machine and heat treat afterwards, or pre-hardened (4140 prehard, about 28–32 HRC), which is machined and ready to use with no heat treatment. At PREMSA we CNC turn and mill it from your file into shafts, axles, mold pins, spindles, bushings and tooling, starting at a single part with an instant price.

CNC machined Steel 4140 heavy-duty components and shafts

Specifications

Steel 4140 Specifications

Engineering-grade properties of Steel 4140, including strength, toughness, and heat-treatment response. This alloy steel is widely used in critical applications where fatigue resistance, impact strength, and reliability are required.

Steel 4140 Engineering Properties

Material Type

Alloy Steel (Chromium-Molybdenum, Cr-Mo)

Primary Characteristics

High strength, excellent toughness, good fatigue resistance, heat-treatable

Tensile Strength (Ultimate)

95–150 ksi (655–1035 MPa, depending on heat treatment)

Tensile Strength (Yield)

60–130 ksi (415–900 MPa)

Shear Strength

≈ 75–95 ksi (517–655 MPa)

Elongation at Break

12–25% (varies with condition)

Brinell Hardness

197–241 HB (normalized), up to ~300+ HB (Q&T)

Density

7.85 g/cm³ (0.284 lb/in³)

Elastic Modulus

29,000 ksi (200 GPa)

Poisson’s Ratio

0.29

Thermal Conductivity

42.6 W/m·K

Coefficient of Thermal Expansion

12.3 µm/m·°C

Melting Range

1415–1540 °C (2580–2800 °F)

Machinability

Moderate (≈ 66% annealed; slower in prehard)

Weldability

Limited (requires preheat and post-weld heat treatment)

Formability

Low (not for cold bending)

Corrosion Resistance

Poor (requires coating or surface protection)

Heat Treatment

Quench and temper; also suitable for nitriding and induction hardening

Common Forms

Bar, plate, pre-hardened stock

Typical Applications

Shafts, axles, spindles, mold pins, bushings, tooling, dies and high-load parts

Material Composition

Iron (Fe): Balance, Carbon (C): 0.38–0.43%, Chromium (Cr): 0.80–1.10%, Molybdenum (Mo): 0.15–0.25%, Manganese (Mn): 0.75–1.00%, Silicon (Si): 0.15–0.35%

ASTM Standard

ASTM A29 / A322

Performance

Material Performance Overview

Rating across key engineering and manufacturing criteria.

Strength

Weight

Machinability

Weldability

Formability

Corrosion Resistance

Thermal Resistance

Cost Efficiency

Need custom 4140 steel parts?

Upload your CAD file and get an instant price and delivery date. CNC turning and milling from one part to production.

Custom 4140 Steel Parts We Machine

We CNC turn and mill 4140 steel parts, annealed or pre-hardened, for machinery, molds, tooling and heavy-duty equipment.

Shafts, axles and spindles

Mold pins and guide pins

High-load bushings and couplings

Tooling, fixtures and dies

Arbors and tool holders

Nitrided wear parts

Oil & gas equipment parts

Heavy machinery replacement parts

High-strength pins and bolts

Material FAQs

4140 Steel FAQs

Common questions about custom 4140 steel parts: what it is, prehard, machining, hardness, welding, tolerances and cost.

Material Guide

4140 Steel: Properties, Machining, Heat Treatment, Tolerances and Finishes

4140 is one of the most widely used alloy steels in industry. Its chromium and molybdenum give it high strength and toughness, and let it through harden even in thick sections. It is available in round, square and plate, annealed or pre-hardened.

At PREMSA Industries we machine 4140 with CNC turning and milling from your file, from prototype to production.

Key manufacturing characteristics of 4140 steel

Chromium-molybdenum alloy steel: about 0.40% carbon, with chromium and molybdenum for strength and toughness.
Through hardens: hardens evenly even in thick parts, not just at the surface.
Annealed or pre-hardened: annealed machines faster and is hardened afterwards; prehard (28–32 HRC) is ready to use off the machine.
Machines well with the right tooling: in CNC milling and CNC turning, with carbide and coolant.
Nitridable: nitriding gives a very hard surface without distorting the part.

Mechanical and physical properties of 4140 steel

4140 is chosen when a part sees high load, impact or fatigue, or has thick sections that must harden evenly.

Typical performance profile

Tensile strength of 655–1035 MPa (95–150 ksi), depending on heat treatment
197–241 HB annealed or normalized and 28–32 HRC pre-hardened
High toughness and impact resistance
Good fatigue resistance
Responds well to nitriding and induction hardening

Why engineers choose it

Handles high load, impact and fatigue
Hardens evenly in thick sections
Available pre-hardened and ready to machine
Easy to source in many sizes

Strengths and advantages of 4140 steel

High strength and toughness: for parts that work hard.
Hardenability: hardens evenly in thick sections.
4140 prehard: the part comes off the machine at final hardness, with no heat treat step.
Nitriding and induction hardening: hard wear surface over a tough core.
Versatile: fits a wide range of parts in CNC machining.

Trade-offs and limitations of 4140 steel

Welding needs care: preheat and, on critical parts, post-weld heat treatment.
Not for bending: it cracks in tight bends.
It rusts: needs oil, black oxide, plating or paint.
Prehard machines slower: more tool wear and more machine time.

Fabrication and machining considerations for 4140 steel

Tolerances on 4140 steel parts

If your drawing doesn’t specify tolerances, we machine to ISO 2768-m (medium). On dimensions you call out we can hold ±0.025 mm (±0.001 in), and critical dimensions are checked in inspection. If the part is hardened after machining, we account for distortion.

Annealed 4140 or 4140 prehard

Annealed 4140 is softer and machines faster; it is then quenched and tempered to the hardness on the drawing. 4140 prehard comes already quenched and tempered to about 28–32 HRC: it is machined directly and the part is finished, with no risk of heat treat distortion.

Heat treating, nitriding and induction hardening 4140

4140 is quenched and tempered to the hardness you need. Nitriding hardens a thin surface layer at low temperature with almost no distortion, and induction hardening hardens only the working area. It is normally not carburized, because it already has enough carbon to harden.

Machining behavior

4140 machines well in CNC milling, CNC turning, drilling and threading with the right tooling.

Carbide tooling and coolant
Lower cutting speeds in prehard
Dimensions that must stay exact after hardening are left with stock for grinding

Welding and joining

4140 can be welded, with process control.

Preheat before welding
Cool slowly and stress relieve afterwards when the part calls for it
Bolted or pinned joints are preferred on critical parts

Finishes and protection for 4140 parts

As machined, with rust-preventive oil
Black oxide
Zinc or nickel plating
Nitriding
Grinding after heat treatment

Common 4140 steel parts

Because of its strength and toughness, 4140 is used in many heavy-duty CNC machined components.

Shafts, axles and spindles
Mold pins and guide pins
High-load bushings and couplings
Tooling and dies
Arbors
Nitrided parts
High-strength pins
Heavy machinery replacement parts

When 4140 steel is a strong material choice

4140 is often the right choice when a part sees high load, impact or fatigue.

When the part transmits power or takes shock loads
When thick sections must be hardened
When you want final hardness without a heat treat step (prehard)
When a surface needs nitriding or induction hardening

Material Overview

What is Steel 4140?

Specifications

Steel 4140 Specifications

Steel 4140 Engineering Properties

Material Type

Alloy Steel (Chromium-Molybdenum, Cr-Mo)

Primary Characteristics

High strength, excellent toughness, good fatigue resistance, heat-treatable

Tensile Strength (Ultimate)

95–150 ksi (655–1035 MPa, depending on heat treatment)

Tensile Strength (Yield)

60–130 ksi (415–900 MPa)

Shear Strength

≈ 75–95 ksi (517–655 MPa)

Elongation at Break

12–25% (varies with condition)

Brinell Hardness

197–241 HB (normalized), up to ~300+ HB (Q&T)

Density

7.85 g/cm³ (0.284 lb/in³)

Elastic Modulus

29,000 ksi (200 GPa)

Poisson’s Ratio

0.29

Thermal Conductivity

42.6 W/m·K

Coefficient of Thermal Expansion

12.3 µm/m·°C

Melting Range

1415–1540 °C (2580–2800 °F)

Machinability

Moderate (≈ 66% annealed; slower in prehard)

Weldability

Limited (requires preheat and post-weld heat treatment)

Formability

Low (not for cold bending)

Corrosion Resistance

Poor (requires coating or surface protection)

Heat Treatment

Quench and temper; also suitable for nitriding and induction hardening

Common Forms

Bar, plate, pre-hardened stock

Typical Applications

Shafts, axles, spindles, mold pins, bushings, tooling, dies and high-load parts

Material Composition

Iron (Fe): Balance, Carbon (C): 0.38–0.43%, Chromium (Cr): 0.80–1.10%, Molybdenum (Mo): 0.15–0.25%, Manganese (Mn): 0.75–1.00%, Silicon (Si): 0.15–0.35%

ASTM Standard

ASTM A29 / A322

Performance

Material Performance Overview

Rating across key engineering and manufacturing criteria.

Strength

Weight

Machinability

Weldability

Formability

Corrosion Resistance

Thermal Resistance

Cost Efficiency

Need custom 4140 steel parts?

Upload your CAD file and get an instant price and delivery date. CNC turning and milling from one part to production.

Custom 4140 Steel Parts We Machine

We CNC turn and mill 4140 steel parts, annealed or pre-hardened, for machinery, molds, tooling and heavy-duty equipment.

Shafts, axles and spindles

Mold pins and guide pins

High-load bushings and couplings

Tooling, fixtures and dies

Arbors and tool holders

Nitrided wear parts

Oil & gas equipment parts

Heavy machinery replacement parts

High-strength pins and bolts

Material FAQs

4140 Steel FAQs

Common questions about custom 4140 steel parts: what it is, prehard, machining, hardness, welding, tolerances and cost.

Material Guide

4140 Steel: Properties, Machining, Heat Treatment, Tolerances and Finishes

Key manufacturing characteristics of 4140 steel

Chromium-molybdenum alloy steel: about 0.40% carbon, with chromium and molybdenum for strength and toughness.
Through hardens: hardens evenly even in thick parts, not just at the surface.
Annealed or pre-hardened: annealed machines faster and is hardened afterwards; prehard (28–32 HRC) is ready to use off the machine.
Machines well with the right tooling: in CNC milling and CNC turning, with carbide and coolant.
Nitridable: nitriding gives a very hard surface without distorting the part.

Mechanical and physical properties of 4140 steel

4140 is chosen when a part sees high load, impact or fatigue, or has thick sections that must harden evenly.

Typical performance profile

Tensile strength of 655–1035 MPa (95–150 ksi), depending on heat treatment
197–241 HB annealed or normalized and 28–32 HRC pre-hardened
High toughness and impact resistance
Good fatigue resistance
Responds well to nitriding and induction hardening

Why engineers choose it

Handles high load, impact and fatigue
Hardens evenly in thick sections
Available pre-hardened and ready to machine
Easy to source in many sizes

Strengths and advantages of 4140 steel

High strength and toughness: for parts that work hard.
Hardenability: hardens evenly in thick sections.
4140 prehard: the part comes off the machine at final hardness, with no heat treat step.
Nitriding and induction hardening: hard wear surface over a tough core.
Versatile: fits a wide range of parts in CNC machining.

Trade-offs and limitations of 4140 steel

Welding needs care: preheat and, on critical parts, post-weld heat treatment.
Not for bending: it cracks in tight bends.
It rusts: needs oil, black oxide, plating or paint.
Prehard machines slower: more tool wear and more machine time.

Fabrication and machining considerations for 4140 steel

Tolerances on 4140 steel parts

Annealed 4140 or 4140 prehard

Heat treating, nitriding and induction hardening 4140

Machining behavior

4140 machines well in CNC milling, CNC turning, drilling and threading with the right tooling.

Carbide tooling and coolant
Lower cutting speeds in prehard
Dimensions that must stay exact after hardening are left with stock for grinding

Welding and joining

4140 can be welded, with process control.

Preheat before welding
Cool slowly and stress relieve afterwards when the part calls for it
Bolted or pinned joints are preferred on critical parts

Finishes and protection for 4140 parts

As machined, with rust-preventive oil
Black oxide
Zinc or nickel plating
Nitriding
Grinding after heat treatment

Common 4140 steel parts

Because of its strength and toughness, 4140 is used in many heavy-duty CNC machined components.

Shafts, axles and spindles
Mold pins and guide pins
High-load bushings and couplings
Tooling and dies
Arbors
Nitrided parts
High-strength pins
Heavy machinery replacement parts

When 4140 steel is a strong material choice

4140 is often the right choice when a part sees high load, impact or fatigue.

When the part transmits power or takes shock loads
When thick sections must be hardened
When you want final hardness without a heat treat step (prehard)
When a surface needs nitriding or induction hardening

4140 SteelCNC Machining

4140 SteelCNC Machining

What is Steel 4140?

Steel 4140 Specifications

Steel 4140 Engineering Properties

Material Performance Overview

Need custom 4140 steel parts?

Custom 4140 Steel Parts We Machine

4140 Steel FAQs

4140 Steel: Properties, Machining, Heat Treatment, Tolerances and Finishes

Key manufacturing characteristics of 4140 steel

Mechanical and physical properties of 4140 steel

Typical performance profile

Why engineers choose it

Strengths and advantages of 4140 steel

Trade-offs and limitations of 4140 steel

Fabrication and machining considerations for 4140 steel

Tolerances on 4140 steel parts

Annealed 4140 or 4140 prehard

Heat treating, nitriding and induction hardening 4140

Machining behavior

Welding and joining

Finishes and protection for 4140 parts

Common 4140 steel parts

When 4140 steel is a strong material choice

What is Steel 4140?

Steel 4140 Specifications

Steel 4140 Engineering Properties

Material Performance Overview

Need custom 4140 steel parts?

Custom 4140 Steel Parts We Machine

4140 Steel FAQs

4140 Steel: Properties, Machining, Heat Treatment, Tolerances and Finishes

Key manufacturing characteristics of 4140 steel

Mechanical and physical properties of 4140 steel

Typical performance profile

Why engineers choose it

Strengths and advantages of 4140 steel

Trade-offs and limitations of 4140 steel

Fabrication and machining considerations for 4140 steel

Tolerances on 4140 steel parts

Annealed 4140 or 4140 prehard

Heat treating, nitriding and induction hardening 4140

Machining behavior

Welding and joining

Finishes and protection for 4140 parts

Common 4140 steel parts

When 4140 steel is a strong material choice

4140 Steel
CNC Machining

4140 Steel
CNC Machining