If your print says stainless but skips the grade, you’re already one step away from a bad decision. 303 and 304 look identical on a shelf but behave very differently at the spindle.
We supply and centerless grind both grades at Advance Grinding Services in Chicago. Pick the wrong one, and you pay for it in tool wear, cycle time, or rejected parts.
303 vs 304 Stainless Steel: What Chicago CNC Shops Need to Know
Both grades are austenitic stainless steels, and both show up constantly in industrial machining. The difference comes down to what you need the part to do after it leaves your shop.
Choosing between them isn’t complicated once you understand the tradeoffs. Machinability pulls you toward 303. Corrosion resistance and weldability pull you toward 304.
303 Machines Faster
303 contains sulfur additives that break the chip during cutting. You get shorter chips, less tool pressure, and faster cycle times. High-volume turned components, shafts, and fittings are where 303 earns its keep.
The tradeoff is corrosion resistance. Those sulfur additives create inclusions that can initiate corrosion in wet or chemical environments. For indoor parts or coated components, that rarely matters. For parts exposed to moisture long-term, it does.
304 Holds Up Longer
304 delivers stronger corrosion resistance across a wider range of environments. It welds cleanly, handles food processing and sanitary applications well, and stays stable where 303 would eventually show surface degradation.
The shop challenge is work hardening. Without free machining additives, 304 grabs and galls more than 303. Chips run stringy. Sharp tooling and consistent coolant discipline manage it, but cycle times run longer than 303.
Ground Bar Stock Changes How Both Grades Run
Bar stock condition directly affects your machining results. Inconsistent diameter and rough surface variation force your machines to compensate, which shows up as chatter and dimensional scatter on finished parts.
We centerless grind both grades to tolerances as low as .0001 inch with micro finish as low as 8 RMS. Diameter range covers .062 inch through 8 inch with lengths up to 40 feet. Clean ground stock means your program runs as written, every time.
Finishing Services for Both Grades
Our polishing stainless steel service improves surface performance and corrosion resistance on both 303 and 304. If your application demands a refined finish, polishing is available as a direct add-on to your ground bar order.
We also offer bar straightening, chamfering, steel cutting, and bar packaging. These services get your material production ready before it reaches your floor, so your team isn’t doing prep work that we can handle upstream.
Other Stainless Grades We Carry
If 303 and 304 don’t fit your spec, our stainless inventory runs well beyond those two grades. We carry 302, 316, 316LVM, 321, 347, 15-5PH, 440C, 446, 455, X15TN, Duplex Bar, and more.
Every grade in our catalog is available as precision-ground round bar stock through our centerless grinding service. If the job needs a tighter spec or a less common grade, reach out, and we’ll confirm availability directly.
Get Precision Ground Stainless Steel Bar Stock from Advance Grinding Services
Tell us your grade, diameter, length, tolerance, and finish requirement. We’ll supply ground bar stock that runs on your machines without extra prep work on your end.
Call us at (708) 442-7100, email sales@advancegrinding.com, or submit your specs through our Request A Quote form at advancegrinding.com. We’re located at 6360 W 73rd St, Suite B, Bedford Park, just outside Chicago.
Frequently Asked Questions
Do you supply 303 and 304 as precision-ground round bar?
Yes. Both grades are centerless ground to tolerances as low as .0001 inch and micro finish as low as 8 RMS, in diameters from .062 inch to 8 inch.
Can 304 stainless steel be machined efficiently on a CNC lathe?
Yes. Sharp tooling, consistent coolant, and precision-ground incoming bar stock reduce work hardening risk and keep cycle times manageable.
What other stainless grades do you carry?
We stock 302, 316, 316LVM, 321, 347, 15-5PH, 440C, 446, 455, X15TN, Duplex Bar, and others. The full list is on our materials page.
What services are available with bar stock orders?
Centerless grinding, polishing, bar straightening, chamfering, steel cutting, bar packaging, and custom machining are all available.
