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La designazione di un cuscinetto radiale a sfere combina una serie dimensionale e un numero di foro, così che un codice come 6204 o 608 fissa in modo univoco diametro interno, diametro esterno e larghezza. L’articolo descrive le cinque serie principali, la lettura del numero di foro, il catalogo di 65 designazioni basato sulla norma JIS e la ricerca inversa a partire dalle dimensioni misurate, sempre legati al generatore di cuscinetti di meta-matic.

Isometric 3D view of a deep groove ball bearing 6204 (bore 20mm, outer 47mm, width 14mm)

Designazioni dei cuscinetti spiegate — 6204, 608 e il catalogo di 65 tipi

Pubblicato 2026-06-22 8 min di lettura

The designation of a deep groove ball bearing — written as 6204 or 608 in three or four digits — is a standardized identification number for its dimensions. As in the "62" of 6204 or the "68" of 6804, the leading size series encodes the cross-sectional dimensions (the balance of outer diameter and width), and the trailing bore number encodes the inner diameter d. This guide explains how to choose among the five major series (68 / 69 / 60 / 62 / 63), how to read the bore number, the bearing size chart of 65 designations drawn from JIS B 1521 / ISO 15, and how to identify a bearing from measured dimensions — all tied to the bearing generator on meta-matic.

What is a bearing designation?

A designation such as 6204 identifies the standardized boundary dimensions of a bearing — bore 20 mm, outer diameter 47 mm, width 14 mm, and minimum chamfer dimension r ≤ 1.0 mm — so any ISO/JIS-compliant bearing with the same designation, regardless of manufacturer, shares the same standardized dimensions. This is the same mechanism by which screw sizes like M3 or M5 uniquely fix the diameter and pitch: the standard guarantees interchangeability. Sealing (ZZ/2RS), internal clearance codes (C2/C3), and precision class codes (P5/P4) are specified separately as suffixes.

Deep groove ball bearing designations follow the standard boundary dimensions defined by JIS B 1521 / ISO 15. Because the four values d / D / B / r are uniquely determined from the designation, writing "use 6204" on a drawing fixes the shaft diameter, housing bore, spacer thickness, and so on. The reverse trap: if you try to choose "a bearing about the same size" without knowing the designation, you can end up with the same d but a different outer diameter or width that no longer fits the existing housing.

Cuscinetto radiale a sfere - Generatore di file STEPBEARINGhttps://meta-matic.com/it/3d/bearing/

Scope of this guide

This guide covers the designations for single-row deep groove ball bearings (open type). The shielded-side suffix ZZ, the contact-sealed suffix 2RS, other bearing forms such as tapered roller bearings or thrust bearings, internal-clearance codes C2/C3/C4, and precision class codes are out of scope.

The two parts of a designation

A designation has two parts: the size series and the bore number. In 6204, 62 is the size series (62 series = medium load) and 04 is the bore number (inner diameter d = 04 × 5 = 20 mm). Within the same series the outer diameter and width change as the bore number changes; with the same bore, the outer diameter and width change as the series changes.

Size series (leading 2 digits) — five options: 68 / 69 / 60 / 62 / 63. Higher numbers mean larger outer diameter and thicker rings, which raise the load capacity
Bore number (trailing 2 digits) — values from 00 to 10. For 04 and above, the number × 5 = inner diameter d (mm) (see § Reading the bore number for details)
Miniature family (688 / 608 and other 3-digit designations) — the trailing single digit directly gives the bore (e.g., 688 is bore d=8 mm, series 68)

Once you internalize this structure, you can read relationships such as "6204 and 6304 share the same bore 20 mm but differ in series" or "6004 and 6204 differ in series but both have bore 20 mm" directly from the designation alone.

The five major series compared

Deep groove ball bearing series are organized into five steps from thin-section to heavy-duty. Lining the five series up at the same inner diameter d = 20 mm (bore number 04) shows the outer diameter and width growing in steps.

Side-by-side comparison of five series of bearings, all with bore 20mm (6804 / 6904 / 6004 / 6204 / 6304) — Figure 2: Five series compared at the same inner diameter d = 20 mm. From left: 6804 (thin) → 6904 → 6004 → 6204 (standard) → 6304 (heavy). Higher series numbers grow both the outer diameter and the width.

Series	Common name	Example at d=20	Outer D / Width B	Typical use
68 series	Extra-thin	`6804`	32 / 7 mm	Small robots, camera gimbals, low-profile mechanisms
69 series	Thin	`6904`	37 / 9 mm	Compact reducers, bicycle hubs, 3D printer moving parts
60 series	Light load	`6004`	42 / 12 mm	Small motors, desktop equipment, the DIY default
62 series	Medium load	`6204`	47 / 14 mm	Most common. Power tools, DC motors, general-purpose machinery
63 series	Heavy load	`6304`	52 / 15 mm	Industrial machinery, high-torque reducers, heavy-load shafts

Table 1: The five major series compared (example at bore d=20 mm)

Start with the `62` series

For DIY, 3D printers, and small mechanisms, if space permits and you want extra load capacity, the 62 series is often the first choice. Compared with the 60 series at the same bore, the 62 series (6200〜6210) has a larger outer diameter and width, which raises the load capacity. Availability is also good. Move on to the 68 / 69 series only when you actually need to make things thinner or lighter — that order leads to the fewest design backtracks.

Reading the bore number

The mapping from bore number (the trailing two digits of a designation) to the actual inner diameter d is a discontinuous lookup table. The values 00 to 03 are irregular, and from 04 onward you can compute the bore mechanically with number × 5 mm.

Bore number	Inner diameter d (mm)	Formula	Example designations
00	10	(irregular)	`6000` / `6200` / `6800`
01	12	(irregular)	`6001` / `6201` / `6801`
02	15	(irregular)	`6002` / `6202` / `6802`
03	17	(irregular)	`6003` / `6203` / `6803`
04	20	04 × 5 = 20	`6004` / `6204` / `6804`
05	25	05 × 5 = 25	`6005` / `6205` / `6805`
06	30	06 × 5 = 30	`6006` / `6206` / `6806`
07	35	07 × 5 = 35	`6007` / `6207` / `6807`
08	40	08 × 5 = 40	`6008` / `6208` / `6808`
09	45	09 × 5 = 45	`6009` / `6209` / `6809`
10	50	10 × 5 = 50	`6010` / `6210` / `6810`

Table 2: Bore number to inner diameter mapping

`00`〜`03` must be memorized

The mapping for bore numbers 00〜03 (10 / 12 / 15 / 17) has no pattern and is the most error-prone part during design. A classic mistake is reading "6200 so the bore is 20 mm" — in fact 6200 has a 10 mm bore (you only reach a 20 mm bore at 6204). From 04 upward you can just multiply by 5, so no memorization is needed.

The miniature family (688 / 698 / 608 / 628 / 638 and so on) puts the bore in the trailing single digit. 688 reads as 68 series, bore 8 mm; 609 reads as 60 series, bore 9 mm. These are dedicated extra-small sizes — the generator currently includes ten miniature variants across the d8 and d9 lineups.

Side-by-side comparison of five miniature bearing series, all with bore 8mm (688 / 698 / 608 / 628 / 638) — Figure 3: Five miniature variants at bore d = 8 mm. From left: 688 (extra-thin) → 698 → 608 → 628 → 638 (heavy). Used in 3D printer extruders, small robot finger joints, and camera gimbals.

Bearing Size Chart (65 Designations)

The following bearing size chart lists the 65 designations that meta-matic can generate, organized by series. The four values d / D / B / r follow the JIS B 1521 / ISO 15 standard boundary dimensions as a reference.

68 series (extra-thin, 11 designations)

Designation	d	D	B	r
`6800`	10	19	5	0.3
`6801`	12	21	5	0.3
`6802`	15	24	5	0.3
`6803`	17	26	5	0.3
`6804`	20	32	7	0.3
`6805`	25	37	7	0.3
`6806`	30	42	7	0.3
`6807`	35	47	7	0.3
`6808`	40	52	7	0.3
`6809`	45	58	7	0.3
`6810`	50	65	7	0.3

Table 3: 68 series (for thinner, lighter designs)

69 series (thin, 11 designations)

Designation	d	D	B	r
`6900`	10	22	6	0.3
`6901`	12	24	6	0.3
`6902`	15	28	7	0.3
`6903`	17	30	7	0.3
`6904`	20	37	9	0.3
`6905`	25	42	9	0.3
`6906`	30	47	9	0.3
`6907`	35	55	10	0.6
`6908`	40	62	12	0.6
`6909`	45	68	12	0.6
`6910`	50	72	12	0.6

Table 4: 69 series (for compact reducers and 3D printers)

60 series (light load, 11 designations)

Designation	d	D	B	r
`6000`	10	26	8	0.3
`6001`	12	28	8	0.3
`6002`	15	32	9	0.3
`6003`	17	35	10	0.3
`6004`	20	42	12	0.6
`6005`	25	47	12	0.6
`6006`	30	55	13	1.0
`6007`	35	62	14	1.0
`6008`	40	68	15	1.0
`6009`	45	75	16	1.0
`6010`	50	80	16	1.0

Table 5: 60 series (DIY standard, small motors)

62 series (medium load, 11 designations, most common)

Designation	d	D	B	r
`6200`	10	30	9	0.6
`6201`	12	32	10	0.6
`6202`	15	35	11	0.6
`6203`	17	40	12	0.6
`6204`	20	47	14	1.0
`6205`	25	52	15	1.0
`6206`	30	62	16	1.0
`6207`	35	72	17	1.1
`6208`	40	80	18	1.1
`6209`	45	85	19	1.1
`6210`	50	90	20	1.1

Table 6: 62 series (the workhorse size for power tools and general machinery)

63 series (heavy load, 11 designations)

Designation	d	D	B	r
`6300`	10	35	11	0.6
`6301`	12	37	12	1.0
`6302`	15	42	13	1.0
`6303`	17	47	14	1.0
`6304`	20	52	15	1.1
`6305`	25	62	17	1.1
`6306`	30	72	19	1.1
`6307`	35	80	21	1.5
`6308`	40	90	23	1.5
`6309`	45	100	25	1.5
`6310`	50	110	27	2.0

Table 7: 63 series (industrial machinery, heavy-load shafts)

Miniature family d=8 / d=9 (10 designations)

Designation	d	D	B	r	Note
`688`	8	16	4	0.2	68 series
`698`	8	19	6	0.3	69 series
`608`	8	22	7	0.3	60 series, skateboard standard
`628`	8	24	8	0.3	62 series
`638`	8	28	9	0.3	63 series
`689`	9	17	4	0.2	68 series
`699`	9	20	6	0.3	69 series
`609`	9	24	7	0.3	60 series
`629`	9	26	8	0.6	62 series (r=0.6 is non-JIS)
`639`	9	30	10	0.6	63 series

Table 8: Miniature family (3D printer extruders, skateboards, small robotics)

Identify a bearing from measured dimensions

For repairs of secondhand machinery or existing equipment, "the bearing in my hand has no readable designation" is a common situation. With a caliper or micrometer you can measure d / D / B and look up the designation in the bearing size chart above. The corner radius r is hard to measure, but if d / D / B do not overlap any other row you can usually narrow down to a single row at that point.

Measure the inner diameter d
Measure the bore diameter with a caliper. This is the dimension with the best measurement accuracy, so anchoring the search to d is the most reliable starting point.
Measure the outer diameter D
Measure the outer ring outer diameter. Combined with d, the series is largely fixed, so measuring D will for a typical deep groove ball bearing usually narrow the result to one of the 68/69/60/62/63 series (the 16000 series, R series, and other specialty parts require separate confirmation).
Measure the width B
Measure the axial thickness with a caliper. Two bearings with the same d / D but a different B are different designations (e.g., 6004 and 6204 share d=20 but have B=12 vs 14).
Cross-check against the chart
Look up these three values in the § Bearing Size Chart and read the matching designation. If r (corner radius) also matches, you are likely looking at a standard series part. If it does not match, it may be a manufacturer-specific size or follow a different standard (ISO / DIN, etc.).

The form can do the reverse lookup automatically

On the meta-matic bearing generator page, entering the four values d / D / B / r automatically shows the matching designation in the REF card. If the dimensions match a JIS standard the designation appears; otherwise it shows CUSTOM. It can be used to identify the part number of an existing bearing whose designation is unreadable.

Cuscinetto radiale a sfere - Generatore di file STEPBEARINGhttps://meta-matic.com/it/3d/bearing/

Generate STEP data

Once you have the designation or the four values d / D / B / r, meta-matic can generate a STEP file for 3D CAD on the spot. Type a designation like 6204 into the designation field on the form and the four dimensions auto-fill. The output loads into major CAD packages such as Fusion 360, FreeCAD, SolidWorks, and Rhinoceros.

What you get is open type (balls only)

meta-matic outputs an open-type STEP file containing three elements: the inner ring, the outer ring, and the balls. Shields (ZZ), contact seals (2RS), the cage, and grease are not included. The output is suitable as a reference shape for drawings or as a placeholder for 3D printing, but if you need true-to-life seal structure, add those parts in your CAD software. The internal groove radius, ball count, and ball diameter are not defined by JIS, so they are generated by an in-house geometric rule (a reference implementation, not full standard conformance).

Also, when mounting a bearing on a shaft, the fit tolerance between the shaft and the bearing inner diameter matters. The bore of a 6204 is nominally 20 mm, but the actual tolerance is on the order of +0 / -0.010 mm depending on the precision class. Whether you make the shaft side a "clearance fit", "transition fit", or "interference fit" depends on the rotation direction, load conditions, and temperature variation. For concrete shaft diameters and tolerance classes, see the ISO fit tolerance calculator.

Frequently asked questions

QWhat is the difference between `6204` and `608`?

The series and the bore are both different. 6204 is 62 series, bore 20 mm (outer 47mm / width 14mm), while 608 is 60 series, miniature family, bore 8 mm (outer 22mm / width 7mm). 6204 is widely used in power tools and motor shafts; 608 shows up in 3D printer extruders and skateboards.

QShould I use the `6000 series` or the `6200 series`?

For availability and cost, pick the 62 series; for lighter or thinner designs, pick the 60 series. The 62 series is easy to find at hardware stores and online and is reasonably priced. With the same bore but a slightly larger outer diameter and width, it carries a higher load capacity. For DIY and 3D printing, treat the 62 series as the first choice and only move to the 60 series when the 62 size will not fit.

QWhat do the `ZZ` and `2RS` in `6204ZZ` or `608-2RS` mean?

They are seal codes. ZZ (or 2Z) indicates two metal shields for a dust-resistant type; 2RS (or 2RU) indicates two contact rubber seals for water- and dust-resistant types. A designation with no suffix (e.g., 6204) is the open type, meaning it has no shields or seals on either side of the bearing to retain lubricant and exclude contaminants. meta-matic only outputs the open-type outer shape — seal parts are not included.

QWhere can I get bearing CAD data?

Manufacturer websites (NTN, SKF, NSK, etc.) typically provide downloads, but they often require account registration or license acceptance and may not cover every designation. meta-matic generates STEP data for all 65 designations with no sign-up and instant download. The dimensions follow the JIS standard, but the internal geometry (ball count, groove radius) follows an in-house rule, so use the output as a reference shape for drawings or 3D layout.

QHow do I choose the bore when sizing a bearing for a shaft?

Pick a bearing whose inner diameter has the same nominal value as the shaft diameter. For a 8 mm shaft, choose from bearings such as 608, 628, or 638 (pick the series by load); for a 20 mm shaft, choose among 6004 / 6204 / 6304 by load. Finish the shaft to a tolerance class such as k5 / m5 (interference fit) or j6 (transition fit) against the bearing bore. See the ISO fit tolerance calculator for details.