High-quality chromium bearing steel balls, 6.35mm-50.8mm, wear-resistant and high hardness.

Product Overview

Solid chrome steel balls, ground all over and supplied across the full size band set out in the specification table below. Four designations cover the same chromium bearing grade: AISI 52100, SUJ2, GCr15 and 100Cr6. Whichever name appears on your drawing, the steel arrives to the same composition window and leaves the plant at HRC 60–66.

We grade the range from G10 to G1000 rather than selling a single tolerance band, and that spread is deliberate. Precision steel balls at the tight end suit high-speed bearing assemblies where play and noise show up immediately; the looser grades cover casters, slides, general machinery and repair work, where the ball has to be hard and round but does not carry a spindle's tolerance requirement.

Production, grinding and inspection all happen in our own plant in Shandong before the balls are packed for export. Sizes from this band also serve as test and impact test balls, where a known, hard, dimensionally consistent sphere is the whole point. If you are matching a ball to an existing bearing, the diameter or the bearing designation is enough for us to confirm what fits; if the application is unusual, tell us the load and speed and we will say plainly whether this grade is the right one.

Specifications

Chromium Steel Chemistry

• Carbon (C): 0.95–1.10% — the element that sets the hardness ceiling. This is the window that lets bearing balls reach HRC 60–66 after heat treatment and hold that hardness under rolling contact.
• Chromium (Cr): 1.30–1.60% — the alloying element behind wear resistance and hardenability, and the reason the grade carries the chromium name.
• Silicon (Si): 0.15–0.35% — held in a narrow band as part of the steelmaking balance. The range is tight so the response to heat treatment stays predictable from heat to heat.
• Manganese (Mn): maximum 0.50% — supports hardenability and is capped rather than targeted, which keeps the steel clean.
• Phosphorus (P): maximum 0.025% — a residual element. The low cap limits embrittlement in a hardened ball that has to survive millions of load cycles.
• Sulphur (S): maximum 0.025% — also residual, and capped for the same reason; sulphur left higher works against fatigue life.
• Why the window is checked — 52100 ball bearing steel outside these limits does not harden evenly across a batch, so the composition is verified against the report before the balls go into production rather than after.

Size Range & Bearing Fit

Inside this band the common imperial steps are all covered: 1/2 inch at 12.7 mm, 3/4 inch at 19.05 mm and 1 inch at 25.4 mm. Metric diameters between those steps belong to the same range.

What changes across the band is load capacity. Diameters around 6–10 mm suit compact assemblies — drawer slides, casters, small gearboxes, hub bearings — where low mass and quiet running matter more than tonnage. The middle, roughly 12–25 mm, covers most wheel bearings, motorcycle and bicycle hubs and general machinery. From 31.75 mm upward the choice is about contact area: large-diameter bearings, heavy machinery and mining or energy equipment use the bigger end so the load spreads instead of concentrating on a small footprint.

Diameter and grade are separate decisions. Two chrome steel balls for bearings of identical size behave very differently if one is G10 and the other G100; match the diameter to the housing first, then take the tightest grade the application can justify.

To identify the size of an existing bearing balls component, measure across the diameter with a micrometer; above roughly 25 mm a vernier caliper is accurate enough. On a worn ball, measure several and use the largest reading, because wear only ever reduces diameter.

Product Advantages

• Hardness that survives the load — bearing steel balls held at HRC 60–66 resist plastic deformation, so a ball does not flatten into an oval and start a vibration problem the rest of the assembly has to absorb.
• Pitting resistance that stretches service intervals — the hardened, ground surface takes rolling contact without breaking down, which is what keeps preload and clearance stable across a long duty cycle.
• Hard through the section, not just at the skin — these are solid steel balls with no plated layer to wear through and expose a softer core, so the surface you specify is the surface you keep.
• A grade ladder instead of one grade — G10 to G1000 from a single product family means a precision spindle position and a general-purpose slide can be specified from the same material and the same source.
• Quiet, smooth running — grinding leaves a fine, bright finish with roundness controlled within the grade, and that reads as lower noise and less vibration in the finished assembly.
• Dimensional stability at speed — a ball held close to true sphere runs true at high rotational speed, where a slightly out-of-round one loads the cage unevenly and shortens its life.

Use Scenarios

Automotive and transmission work is the heaviest use. Wheel bearing assemblies and transmission components run chrome steel balls at continuous rotational speed under load that shifts with every turn and every bump, and the assembly depends on the ball keeping its diameter and roundness through that cycle. Because the band covers the sizes these assemblies draw on, one shipment can serve several positions.

Motorcycle and bicycle hubs, casters, luggage wheels, drawer slides and telescopic rails take the small and middle sizes, where the ball is a rolling contact rather than the primary load path. Electronics assemblies and small mechanisms behave the same way: roundness, hardness and consistency matter more than raw diameter.

Maintenance and repair is the other steady demand. Plants replacing worn balls in pumps, gearboxes, conveyors and general rotating equipment buy steel balls for bearings by size, and the hardness band is what restores a machine to its original clearance instead of leaving it loose. Energy and mining operations use the large end the same way, where a 40 mm or 50.8 mm ball carries load a small ball simply cannot.

A separate use sits outside rotating equipment. Sizes from this band are bought as test and impact test balls, where the requirement is a known, hard, dimensionally consistent sphere that behaves the same way on every drop and every cycle.

Inspection & Test Methods

1. Rockwell hardness test. Hardness is read on a Rockwell tester and reported on the HRC scale. Balls from this line normally sit at HRC 60–66; for comparison, stainless balls generally measure around HRC 26 and carbon steel balls HRC 55–65, with soft carbon steel around HRC 30. Hardness is the first thing a buyer checks on steel balls for bearings, because it predicts how the ball behaves under load rather than how it looks.
2. Roundness check on a roundness meter. The high-precision end of the range — the G5 and G10 classes — is measured for ellipticity, meaning the deviation from a true sphere. The instrument plots the ball's profile so the deviation can be read directly instead of inferred from a diameter reading.
3. Diameter check with a digital micrometer. Tolerance is the number that decides fit, so diameter is checked with a micrometer or spiral micrometer. Large balls in the upper part of the range are measured with a vernier caliper.
4. Batch review before packing. The material is backed by a test report on the bearing steel ball sample, and a batch is released on its hardness, roundness and diameter results rather than on a visual pass.

Production Capacity

• 150,000 pieces a month on this size band — output from a ball bearing manufacturer that also absorbs replacement quantities without a separate production set-up.
• The full band from one line — every diameter we list comes off the same line, so a mixed-size order leaves together instead of being split across two suppliers and two freight bookings.
• G10 to G1000 in the same material — precision and general-purpose grades of chromium steel balls produced on the same line, so a specification change does not turn into a supplier change.
• Repeat runs to the same window — the steel is bought to the 52100 ball bearing steel composition every time, which is what makes the tenth order behave like the first.
• Capacity quoted per size and grade — tell us the monthly draw for each diameter and we can plan a standing requirement instead of quoting it order by order.

Packaging, Shipping & Ordering

1. Send the size, grade and quantity. Diameter in millimetres or inches, the grade you want, and how many pieces — that is what we need to quote a shipment of precision steel balls. Quotations depend on size, grade, quantity, packing and freight, so a complete list gets you an exact figure rather than a range.
2. Choose the packing. Standard export packing is a 20 kg carton with a woven bag liner; we also supply cartons on pallets and drums on pallets, and can pack to your own requirement if your warehouse has a receiving standard.
3. Choose the shipping method. Sea freight for pallets and drums, air freight for urgent part loads, and express for small quantities.
4. Nominate the port. We ship from Qingdao, Tianjin, Shanghai and Ningbo — tell us which is closest to your destination and we route from there.
5. Confirm the schedule. Delivery is stated as 3–5 days after order, depending on order quantity. Confirm the current schedule for your size and volume before you plan around it.
6. Check a sample first if the fit matters. If the ball has to go into an existing assembly, ask your sales contact about sample availability and the current terms before you commit to a production run.

Wet & Corrosive Environments

• Chromium bearing steel is a through-hardened grade, not a stainless one. The 1.30–1.60% chromium in AISI 52100 — also sold as SUJ2, GCr15 and 100Cr6 — is there to harden the steel; it does not build the passive surface layer that keeps 304 or 316 bright in wet service. Leave a chrome steel ball standing in water and it rusts.
• Where it belongs is a sealed or lubricated assembly. Wheel hubs, gearboxes, transmissions and grease-packed bearings run these chromium bearing steel balls behind a seal, with an oil or grease film between ball and raceway. That film is the corrosion protection, so the specification holds only as long as the lubrication and the seal hold.
• What moisture actually costs: a rust bloom on a ball or raceway is not cosmetic. The corrosion product is abrasive, it pits the running surface, and the pitting turns into noise and then spalling. A few weeks of damp storage can spoil a batch of solid steel balls, and a bearing that fails early turns a re-order into a full rebuild.
• Switch to stainless when the position sees washdown, condensation, process water or a mildly acidic or alkaline medium. 440C holds HRC 58–62 with the corrosion resistance 52100 lacks, which is why it is the usual grade in pumps, aerosol pumps, sprayers and valve seats. For marine atmosphere, sulphuric, phosphoric or acetic acid, 316 is the choice — non-magnetic and the most corrosion-tolerant of the three. 304 covers general wet handling at light load.
• Weigh the trade-off before you substitute. 440C is softer than the HRC 60–66 band of this line, so a heavily loaded position does not simply take a stainless ball in place of a chromium one. High load with occasional moisture is usually better served by keeping the chromium grade and protecting it with grease; constant moisture means accepting lower hardness or changing the housing design.
• Keep the balls dry until they are fitted. Leave them in the sealed inner bag inside the 20 kg carton until the line is ready, store the carton off a concrete floor in a dry area, and never park an opened bag beside a coolant mist or an open wash bay. If a carton comes in from a cold container into a warm shop, let it reach room temperature still closed so the condensation lands on the carton and not on the balls.
• Wipe, do not wash. A ball with handling marks can be wiped with an oiled cloth; water-based cleaners and a wet rag leave moisture exactly where rust starts first. Spare precision steel balls kept as a maintenance item belong in an oiled bag or a sealed tin, not in an open bin on the bench.
• Tell us the duty when you order: the medium, the temperature, whether the position is greased and sealed, and whether the machine is washed down. As a ball bearing manufacturer we would rather ask about the environment up front than see a batch fail in the field — with those details we can say whether steel balls for bearings from this chromium line are the right call, or whether the position should be filled from our 440C or 316 range.

Scale & Supply Capability

Yuncheng Kangda Steelball Co., Ltd., the factory behind the Condar brand, has been producing precision balls in Shandong, China since 2014 with a team of 80. Two factories handle production, while a 2,000 m² warehouse inside the Liaocheng logistics park keeps common sizes in stock so ordered sizes can leave quickly. More than a hundred sets of production and inspection equipment work to GB/T308.1-2013, backed by ISO documentation and RoHS/REACH material statements. Customised or made-to-order items can be quoted case by case.

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