4140 steel, commonly known as Chromoly steel, delivers a compelling mix of strength, toughness, and wear resistance. Ideal for high-stress components like shafts, gears, and machinery parts, 4140 round bars come in various diameters and finishes, including annealed and cold-finished options. This article highlights five practical 4140 round bars available online, with a quick comparison and a buying guide to help you choose the right size, finish, and heat treatment for your project.
| Product | Diameter | Length | ||
|---|---|---|---|---|
| 4140 Alloy Steel Round Bar, Unpolished (Mill) Finish, Annealed | 0.6875 in | 12 in | Annealed | General high-strength components |
| 0.937 x 36 inches, 4140 Round Rod, Cold Finished | 0.937 in | 36 in | Cold Finished | Machinable stock for precision parts |
| 1-1/8″ Round Bar, 4140 Cold Drawn | 1.125 in | Length selectable | CD HT (Cold Drawn, Heat Treated) | High-tolerance components |
| 4140 Alloy Steel Round Bar, Unpolished (Mill) Finish, 0.75″ Dia, 12″ Len | 0.75 in | 12 in | Annealed | Durable, high-stress parts |
| 4140 Alloy Steel Round Bar, 1.5″ Dia, 12″ Len | 1.5 in | 12 in | Annealed | Heavy-duty shafts and components |
4140 Alloy Steel Round Bar, Unpolished (Mill) Finish, Annealed
Size and finish match common machining and welding workflows. The bar is 0.6875 inches in diameter and 12 inches long with an annealed state, suitable for forming, drilling, or threading in intermediate-strength applications. Recognized for its abrasion and impact resistance under high stress, 4140 steel (Chromoly) combines hardness and toughness for durable components.
0.937 (15/16 inch) x 36 inches, 4140 Round Rod
This cold-finished 4140 round rod measures 0.937 inches in diameter and 36 inches in length, offering a good balance between machinability and core strength. Cold finishing helps improve dimensional stability and surface finish, making it a practical choice for components requiring tight tolerances and consistent performance in high-load environments.
1-1/8″ Diameter Round Bar, 4140 CD HT
This 4140 cold-drawn steel rod is 1.125 inches in diameter with heat-treated properties and a length tolerance of plus/minus an eighth inch. The CD HT designation indicates a controlled hardness suitable for precision shafts, pins, and wear-resistant components where tight tolerances matter in demanding applications.
4140 Alloy Steel Round Bar, 1.5″ Dia, 12″ Len
With a 1.5 inch diameter and a 12 inch length, this annealed 4140 round bar is suited for heavier duty fabrication. The Chromoly steel’s combination of strength, fracture resistance, and impact tolerance makes it a common choice for structural and mechanical components subject to high stress and wear.
1-1/8″ Diameter Round Bar, 4140 CD HT
The 1-1/8″ diameter 4140 CD HT variant emphasizes tight tolerances and consistent hardness across the bar. Suitable for precision components and shafts where controlled machining and wear resistance are essential for long-term reliability in mechanical assemblies.
0.937 (15/16 inch) x 72 inches, 4140 Round Rod
This extended-length 0.937 inch diameter rod provides ample material for fabrication of longer shafts, pins, or rods that require robust mechanical properties. The cold-finished surface aids in smoother machining and improved dimensional control, suitable for production runs of moderate length.
Buying Guide: Key Purchase Considerations
Material and heat treatment: 4140 steel offers high strength and toughness due to chromium content. Decide between annealed, milled, or cold-finished states and whether heat treatment (CD HT) is needed for hardness and wear resistance based on your application. Finishes affect machinability and surface quality, with annealed bars typically easier to machine but requiring post-machining hardening for certain uses.
Diameter and length: Choose exact diameters to fit bearings, shafts, or sockets, and confirm available lengths match your fabrication plan. Longer bars may reduce waste in milling and allow for multiple parts, while shorter bars can minimize material cost for single-piece projects.
Dimensional tolerances: 4140 CD HT and cold-finished variants often deliver tighter tolerances, which is crucial for precision components. If your project demands strict tolerances, verify tolerance allowances with the supplier before purchase.
Availability and sourcing: Online retailers offer a range of diameters and finishes in stock. Consider lead times, packaging, and whether the product ships as bars or cut-to-length pieces. Availability can influence project scheduling and inventory planning.
Cost considerations: While prices are not listed here, 4140 products vary by diameter, length, and heat treatment. Compare options that meet strength requirements without oversizing, to optimize material use and overall project cost.
Corrosion resistance and surface finish: 4140 is not inherently corrosion-proof; consider coatings or protective finishes if used in outdoor or humid environments. Annealed finishes provide ease of machining, while hardened or cold-finished variants offer better wear resistance for moving parts.
Application alignment: Match the product’s strength, ductility, and hardness to your application. For high-stress shafts or wear components, CD HT or hardened finishes may be preferable. For general fabrication or prototypes, annealed or milled finishes may suffice.