0.5mm-5.0mm metal ball head G10-G200 small steel ball

Range Overview

Ground from GCr15 chromium steel — sold elsewhere as AISI52100, SUJ2 or 100Cr6 — these bearing steel balls run in grades G10 through G200 at HRC60–66. The band is deliberately miniature: it covers instrument bearings, small motors, valve seats, dosing pumps and compact guide mechanisms, where the rolling element is only a few millimetres across and still carries load thousands of times an hour.

Grade is what separates one order from another here. G10 holds the tightest tolerance in the range and G200 the most relaxed, so the same steel can serve a fine instrument or a repair shelf. Each diameter and grade is a separate line, which lets a buyer take 1.5 mm, 2.5 mm and 4 mm in one shipment instead of splitting the requirement.

Most buyers are bearing and component manufacturers, maintenance departments holding replacement stock, and hardware distributors supplying repair shops. If you are weighing precision steel balls against a general-purpose grade for the same fit, the grade number — not the steel — is what decides running accuracy.

Technical Specifications

Chrome Steel Chemistry

• Four designations, one steel — GCr15, AISI52100, SUJ2 and 100Cr6 all name the same chromium-bearing grade, so a drawing written to GB, ASTM, JIS or DIN supports the same 52100 ball bearing steel.
• Carbon 0.95–1.10% — the high-carbon base allows through-hardening to HRC60–66, so hardness runs through the whole section rather than sitting in a case.
• Silicon 0.15–0.35% — held in this band for deoxidation during melting; a controlled level keeps the steel clean and predictable at hardening temperature.
• Manganese maximum 0.50% — adds hardenability without pushing the steel toward retained austenite after quenching.
• Phosphorus maximum 0.025% — kept low because phosphorus embrittles grain boundaries, and a ball of one or two millimetres has very little material to absorb that.
• Sulfur maximum 0.025% — held to the same low limit; sulfur inclusions are where rolling-contact fatigue usually begins.
• Chromium 1.30–1.60% — the alloying element behind the wear resistance and dimensional stability of these bearing steel balls under repeated load.

Diameter and Grade Selection

Diameter follows the space the ball has to work in. Balls from 0.5 mm to about 1.5 mm go into the smallest instrument and motor bearings, where a fraction of a tenth of a millimetre shifts preload; 1.5 mm to 3 mm is the working middle of the range and covers most miniature bearing units, small pumps and control mechanisms; 3 mm to 5 mm suits small bearings, valve seats and slide contacts that carry more load and can accept a larger element. All of them are cut from the same 52100 ball bearing steel, so the diameter you choose does not change the grade of steel behind it.

The grade decides how closely each ball is held to a true sphere and to nominal size. G10 is the tightest option here and G200 the loosest. Tight grades make sense where several balls share a load and any variation shows up as play or noise; looser grades are the practical choice for repair stock, slow mechanisms and general hardware, and they cost less per piece. A common mistake is putting the tightest grade into a housing that was machined loosely — the assembly cannot use the extra accuracy.

When you specify steel balls for bearings, give the diameter, the grade and the material together, exactly as they appear on the drawing or on the worn part. Those three lines are enough to quote against, and they prevent the usual mix-up between a 3 mm G10 and a 3 mm G200 line.

Where These Balls Work

• Miniature bearing units — the main use. These bearing steel balls sit inside small radial and instrument bearings, where a consistent diameter keeps preload even around the raceway.
• Small motors and instruments — armature supports, meter movements, encoder bearings and other low-torque assemblies that notice drag immediately.
• Valves and pump components — check valves, dosing pumps and small piston pumps use them as seats and non-return elements, where hardness resists indentation from repeated seating.
• Slides, rails and hardware — drawer slides, luggage wheels, cabinet fittings and electronics assemblies that need smooth rolling contact in a small envelope.
• Bicycles, motorcycles and automotive small parts — the same small steel balls appear in cable ends, small linkages and compact mechanisms across these assemblies.
• Repair and maintenance stock — workshops keep a short range of diameters on the shelf to restore a unit rather than replace it, and a mixed-diameter order covers most of that shelf in one delivery.

Inspection and Test Methods

1. Hardness is checked on a Rockwell tester and recorded as an HRC value; balls in this range sit at HRC60–66, while the same bench reads stainless balls at roughly HRC26, carbon steel at HRC55–65 and soft carbon steel near HRC30.
2. Roundness is measured on a roundness meter, which traces the sphere and reports ellipticity — the check that separates G5 and G10 bearing steel balls from a general-purpose grade.
3. Diameter and tolerance are verified with a micrometer or spiral micrometer ball by ball, with vernier calipers reserved for larger sizes where hand measurement is accurate enough.
4. Results travel with the shipment, documenting the grade, hardness and material figures we quote for a batch.

Monthly Output and Supply

Monthly output on this range is 1,586,000 pieces, which matters when the balls are a repeating line rather than a one-off purchase. As a ball bearing manufacturer running to a fixed production schedule, we can hold a grade and diameter combination steady across consecutive lots, so the second delivery behaves like the first and your assembly settings do not have to be adjusted each time.

The practical gain for buyers running several small parts is consolidation: the full range on one purchase order and one set of documents. Sharing your forecast early helps, because a scheduled call-off on the steel balls for bearings you use most keeps stock planning simple on both sides. Mixed diameters ship together, and repeat orders keep the same grade reference from lot to lot.

Ordering, Packing and Delivery

• Quote the line precisely — diameter, grade, material and quantity. This range is supplied as chrome steel balls in GCr15 / AISI52100 / SUJ2 / 100Cr6, and a diameter without a grade cannot be priced correctly.
• Standard packing — 20 kg/carton packaging woven bags, carton+pallet, or drum+pallet, depending on the size mix and how the goods will be handled at your end. If your line needs a different format, raise it when you order and it can be confirmed.
• Shipping modes — sea freight, air freight or express. Small quantities usually move by express; full cartons go by sea or air.
• Ports of shipment — Qingdao, Tianjin, Shanghai and Ningbo Port, selected to match your destination and the sailing schedule.
• Delivery — 3–5 days after the order, depending on order quantity. Confirm the current lead time with your sales contact before you plan a line stop around it.
• Samples and payment terms — ask your sales contact about sample availability and the terms that apply to your order.

Surface Finish & Rolling Contact

Ground all over, not polished for show

Every ball in this range leaves production ground. Grinding is the operation that brings a formed sphere to its nominal diameter and its roundness at the same time, so the surface you receive is the surface the grade was measured on — the same face the micrometer and the roundness meter checked. It comes up bright and even grey, with a fine directional pattern visible under a magnifier on the looser grades and a smoother, more uniform texture as you move toward G10.

Finish matters because a rolling element does not carry load at a point. Inside a miniature bearing the ball touches the raceway over a small ellipse, and any roughness peak within that ellipse takes far more than its share of the stress. A ground face spreads contact evenly across the whole patch, which is what keeps preload stable around the raceway and stops running torque from climbing as speed rises. A cosmetically polished ball can be right at its equator and vague near its poles; in an assembly built from small steel balls, a few micrometres of that vagueness is enough to show up as noise, or as play you cannot adjust out.

Surface and lubrication work as a pair. The finer the finish, the thinner the oil film that can still separate ball from raceway, so ground balls suit low-viscosity grease and lightly lubricated instrument mechanisms where a rougher surface would run metal on metal. Where the film is marginal, roughness peaks are also where a chrome steel balls assembly starts to pit: the peak yields, the pit grows, and the debris it sheds damages the rest of the race. That is why finish and hardness are specified together rather than one without the other.

What arrives is bare, unplated 52100 ball bearing steel. There is no coating to wear through and no colour layer to chip — and equally no corrosion barrier, so keep cartons sealed until the balls go into the line and keep the storage area dry. If your drawing calls for a decorative or coloured finish rather than a rolling surface, tell us when you enquire: a plated or mirror-polished ball is a different product, built for appearance rather than for load. For a precision steel balls order, the practical question is not how shiny the ball looks but whether grade, diameter and ground finish belong to one specification — and that is what we quote and inspect against.

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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