At O’Hare Precision Metals, we’ve supplied precision-ground alloy steel round bar since 1970. Aerospace engineers call us regularly for one grade above all others. That grade is 4340, a nickel-chromium-molybdenum alloy built specifically for structural applications where toughness is non-negotiable.
4340 shows up on more aerospace drawings than any other grade in its family. Aircraft structural components and automotive crankshafts both demand a material that holds up under dynamic, cyclic loading. The Ni-Cr-Mo combination in 4340 delivers exactly that, which is why engineers keep coming back to it.
What Makes 4340 the Right Choice for Aerospace Structural Applications
4340 is for aircraft and automotive crankshaft applications because its nickel-chromium-molybdenum system produces high toughness. Toughness means the material resists fracture under dynamic load, not just static stress. Parts that see vibration, impact, and cyclic loading throughout their service life need that property built into the alloy itself.
Other grades like 4130 and 4140 serve aerospace work well in the right context. But 4130 leads with machinability and weldability for thinner sections. 4140 leads with wear resistance for highly stressed industrial parts. When the structural demand is higher, and toughness is the deciding factor, 4340 is the grade that fits.
How Precision Grinding Prepares 4340 for Your Machining Operation
We centerless grind 4340 round bar to tolerances as tight as .0001 inches, with a surface finish of 8 micro inches or better. That means your shop receives a bar that’s already in dimension. You don’t spend too much time correcting a surface that should have been right before it arrived.
Our grinding capability covers diameters up to 9 inches and lengths up to 50 feet. The specialized grinding division handles up to 7-inch diameter and 24-foot lengths. CNC and manual OD grinding are both available, with in-process gauging running during the cycle to confirm accuracy before the bar ships.
Companion Services Available With Your 4340 Order
Our CNC automated saws cut up to 7-inch diameter using cold saw blades. Cold sawing produces cleaner ends and tighter length tolerances than bandsaw or friction sawing methods. Turning is available for reducing OD to a specified dimension on both short and long pieces.
Custom machining covers pockets, holes, flat surfaces, slots, and complex contours on solid bars, forgings, and castings. Roller burnishing is also available for shaft fillets and sealing surfaces. That process creates compressive residual stress, which improves fatigue resistance on high-stress components.
Quality Standards Behind Every Order
We are ISO 9001:2015 certified, and quality control inspections run at each phase of our operations. That applies to every alloy steel order we process, including 4340 round bar. Aerospace procurement teams get a documented, auditable quality system, not a verbal guarantee.
Every phase of our operation runs through consistent inspection before the next step begins. From raw material selection through grinding, cutting, and packaging, each step is checked. That process has been part of how we work since we started in the Chicago area in 1970.
Other High-Performance Grades We Carry for Aerospace Programs
Aerospace programs pull from a wide material list beyond 4340. We carry 4130 for aircraft and hydraulic applications, 52100 for aircraft bearings and highly stressed parts, and 9310 for crankshafts and heavy-duty gear shafts. All are available as precision-ground round bar.
For high temperature and corrosion critical needs, our nickel alloy inventory includes Inconel, Hastelloy C22, and A286, an iron-nickel-chromium grade for jet engine fasteners and high temperature parts. Titanium bar stock is available across multiple grades, including Grade 5 Ti 6Al-4V, for aerospace, marine, and medical applications.
Get Precision Ground 4340 Steel Round Bar From a Supplier You Can Count On
We’ve been supplying precision-ground alloy steel round bar to aerospace, automotive, and industrial manufacturers since 1970. Every order runs through our ISO 9001:2015 certified quality system, with inspections at each phase before anything ships. That’s not a claim. That’s a process we’ve held to since we started in the Chicago area.
Our in-house capabilities cover centerless grinding, CNC saw cutting, turning, custom machining, burnishing, and packaging, all under one roof. You specify the material, tell us what processing you need, and we handle it. No coordinating between multiple vendors, no chasing tolerances after the bar arrives at your shop.
Request a Quote for 4340 Steel Round Bar Today
Superior in Steel Production and Machining Operations, that’s the standard we’ve held since 1970. Tell us your diameter, length, tolerance requirement, and any downstream processing you need. We’ll get back to you with what you need to move forward on your specific application.
Every quote request goes directly to our team at 2404 W. Hamilton Rd., Arlington Heights, IL. Whether you’re sourcing a single grade or building out a full material list for an aerospace program, we’re ready to help you get it right the first time.
Call: (847) 640-6050 Email: sales@ohareprecision.com Quote Form: ohareprecision.com/request-a-quote Hours: Monday through Friday, 9:00am to 5:00 pm CST
FAQs
Why do aerospace engineers choose 4340 over 4130 or 4140?
4340 delivers high toughness through its Ni-Cr-Mo system. 4130 leads in machinability and weldability. 4140 leads in wear resistance. For structural toughness, 4340 is the right grade.
What tolerances can you hold on a 4340 round bar?
We grind to tolerances as tight as .0001 inches with a surface finish of 8 micro inches or better, up to 9-inch diameter and 50-foot lengths.
Is O’Hare Precision Metals ISO certified?
Yes. O’Hare Precision Metals is ISO 9001:2015 certified, with quality control inspections running at each phase of every order we process.
What additional processing can I add to my 4340 order?
CNC saw cutting, turning, custom machining, roller burnishing, and packaging options, including tube and collar wrap and custom wood boxes.