6203 Bearing Dimensions

Tolerances and fits for 6203

FULI makes 6203 to P0 as standard, with P6 on request. P0 is the Normal tolerance class of ISO 492; P6 limits are tighter. These are the P0 limits for the 17 × 40 × 12 mm size.

Dimension	Nominal, mm	Deviation, µm	Limits, mm
Bore d (Δdmp)	17	0 / −8	17.000 / 16.992
Outside diameter D (ΔDmp)	40	0 / −11	40.000 / 39.989
Width B (ΔBs)	12	0 / −120	12.000 / 11.880

Δdmp and ΔDmp: deviation of the mean bore and mean outside diameter in one radial plane. ΔBs: inner ring width; the outer ring width has the same limits.

Shaft and housing fits (general guidance)

For an inner ring that turns with a solid steel shaft under normal load, bearing makers’ fit tables give 17 j5 for the shaft of 6203. The housing bore is usually H7, or J7 where the outer ring must not creep.

Seat	Deviation, µm	Limits, mm	Fit with 6203
Shaft 17 j5	+5 / −3	17.005 / 16.997	13 µm interference to 3 µm clearance
Housing 40 H7	+25 / 0	40.025 / 40.000	0 to 36 µm clearance
Housing 40 J7	+14 / −11	40.014 / 39.989	11 µm interference to 25 µm clearance

Taking the loosest and the tightest combination of limits, a P0 6203 on a 17 mm j5 shaft has 13 µm interference to 3 µm clearance. Its outer ring has 0 to 36 µm clearance in an H7 bore and 11 µm interference to 25 µm clearance in a J7 bore.

This is general guidance, not a FULI specification. Heavy or shock loads, a hollow shaft, a thin-walled, split or light-alloy housing, or a large temperature difference between shaft and housing call for other classes, and the drawing of your machine takes priority. A tight shaft fit or a hot housing uses up internal clearance, and that is when C3 is chosen instead of C0.

If the outer ring turns and the shaft stands still, as in an idler pulley or a wheel hub, the fits are reversed: the housing gets the interference fit (for example N7 or P7) and the shaft a sliding one (g6 or h6).

Sources: ISO 492 tables as printed in the NTN catalogue CAT. No. 2203/E (Tables 6.4 and 6.5) and the RKB tolerance catalogue; ISO 286-2 for the seats; SKF and NTN fit tables for the shaft and housing classes.

The 6203 bearing dimensions are 17 mm bore, 40 mm outside diameter and 12 mm width. The 17 mm shaft sits between the small appliance sizes and the 20 mm shafts of light industrial machines, and the 6203 turns up in motorcycle rear wheels and gearboxes, small pumps, electric motors and fans. This page explains the designation, gives the catalog figures for our 6203, and lists the checks that stop a wrong size or a wrong seal from reaching your warehouse.

6203 bearing dimensions explained

A 6203 is a single row deep groove ball bearing in the 02 dimension series: 6 for the bearing type, 2 for the diameter series, 03 for the bore [1].

The bore code 03 does not mean 15 mm. The rule “bore code times 5” only starts at 04. Codes 00 to 03 are fixed values, and 03 is 17 mm [1]. The 17 mm bore is the reason 6203, 6003 and 6303 share a shaft, not a housing.

The boundary dimensions follow the ISO 15 general plan [2], so 17 x 40 x 12 mm is the same in every catalogue. The chamfer at the ring corners is set as a minimum value, not a fixed one, so check it only if your drawing calls it out.

In inches, 17 x 40 x 12 mm is 0.6693 x 1.5748 x 0.4724 in. Our catalog gives a basic dynamic load rating Cr of 8.64 kN, a static rating C0r of 4.60 kN and limiting speeds of 17,000 r/min with grease and 20,000 r/min with oil. Values from FULI’s catalog; confirm for your application.

Each 6203 weighs 0.067 kg in our catalog, so 100 pieces are about 6.7 kg before boxes and cartons.

6203 load rating in context

A load rating means more next to the alternatives. For the 17 mm shaft, our catalog figures are:

Model	Size (mm)	Cr (kN)	C0r (kN)	Weight (kg)
6003	17 x 35 x 10	6.12	3.22	0.041
6203	17 x 40 x 12	8.64	4.60	0.067
6303	17 x 47 x 14	12.15	6.29	0.113

Values from FULI’s catalog; confirm for your application.

Going from 6203 to 6303 adds about 40% to the dynamic rating, but the housing bore grows from 40 to 47 mm. That trade is only open at the design stage. On a replacement job the housing decides, and the 6203 stays a 6203.

6203ZZ, 6203-2RS or open

The three versions share the same envelope. The suffix tells you what covers the gap between the rings.

Version	Cover	Typical 6203 position
6203 open	None	Motorcycle gearbox shafts running in engine or gearbox oil
6203ZZ	Two non-contact steel shields	Small motors and fans in clean, dry places
6203-2RS	Two rubber contact seals, greased	Rear wheel hubs, water pumps, outdoor equipment

Sealed bearings keep dirt out better than shielded ones, and shielded better than open [3]. In a pump, water that runs along the shaft from a dripping shaft seal is what kills the bearing. A shield leaves a gap at the inner ring and will not stop it. Our page on water pump bearings explains the sealing choice in more detail.

An open 6203 in a gearbox depends on the gearbox oil. Do not replace it with a 2RS “to be safe”. The seals keep the oil out and the bearing then runs only on its factory grease.

6203 clearance: what to write on the order

A bearing with no clearance suffix is Normal clearance, CN or C0. For a 17 mm bore, NTN’s table gives C2 as 0 to 9 μm, CN as 3 to 18 μm and C3 as 11 to 25 μm [4].

NSK lists larger-than-normal clearance for tight fits on both rings, a hot inner ring, heavy or shock loads and high speeds [5]. Several of those conditions meet in a pump, and pump bearings are commonly ordered C3. A gearbox or motorcycle engine position can also call for C3 or a special group; the old bearing’s marking tells you.

The fit matters as much as the group. Where the shaft turns and the load points one way, the inner ring needs an interference fit and the outer ring can be a looser fit [5]. An interference fit expands the inner ring and takes up part of the clearance [5]. A 6203 pressed onto an oversize shaft with Normal clearance can end up with no clearance left once it is warm. If you are copying an existing design, copy the clearance group as well as the size.

Clearance is set on automatic assembly equipment in our factory and checked periodically during production. It cannot be changed after the bearing is built, so write it in the full code, for example 6203-2RS C3.

Where the 6203 is used

These are the positions where the 6203 appears on our application pages:

• Motorcycle bearings: rear wheel hubs, usually 2RS, and gearbox shafts, usually open and running in oil.
• Water pump bearings and electric motor bearings: the 17 mm shaft line in the size tables, with the 6303 as the heavier choice.
• Fan and blower bearings: the 17 mm line of the 6200 and 6300 table.

A deep groove ball bearing takes radial load and some axial load in both directions [3], which suits a wheel hub with side load in corners and a pump with a small axial pull from the impeller.

Common 6203 ordering mistakes

Same shaft, different series. The 17 mm bore comes in at least six series on our specification sheet: 6803 (17 x 26 x 5), 6903 (17 x 30 x 7), 16003 (17 x 35 x 8), 6003 (17 x 35 x 10), 6203 (17 x 40 x 12) and 6303 (17 x 47 x 14). The 6403 goes to 17 x 62 x 17 mm. Measuring only the bore narrows nothing down.

A neighbour one size away. The 6202 is 15 x 35 x 11 mm and the 6204 is 20 x 47 x 14 mm. On a motorcycle, front and rear wheel bearings are often different sizes, and a set ordered from one wheel will not suit the other.

An inch-bore bearing with a 6203 number. Bearings with a 6203 number and an inch bore are sold for some equipment. If the bore measures about 15.9 mm, close to 5/8 in, the old bearing is not a standard 6203. Send the full marking and the measurements and we will tell you what it is and whether we can supply it.

Letters left off. Inquiries often say “6203” and nothing else. The supplier then quotes the open bearing with Normal clearance, because that is what the bare number means. If you need 6203-2RS C3, write 6203-2RS C3. Our guide on how to avoid ordering the wrong bearing goes through the suffixes.

How to measure a 6203

1. Clean the bearing and measure the bore at two points, 90° apart: 17 mm.
2. Measure the outside diameter at two points: 40 mm.
3. Measure the width across both rings: 12 mm.
4. Read the ring face or shield for the designation and suffix.
5. Check the cover: rubber seals (2RS) or steel shields (ZZ), on one side or both.

If the three numbers are 17, 40 and 12 mm, it is a 6203 whatever the brand on the ring. If they are not, our bearing size finder finds the size from the measurements.

How we supply the 6203

Our 6203 rings and balls are GCr15 chrome bearing steel. The steel maker’s material certificate is available on request for OEM and industrial orders. Precision is P0 as standard and P6 on request.

Sealed and shielded 6203 bearings are greased to about 30% of the free space inside the bearing. The filling machine is set from the weight of grease in sample bearings, weighed before and after filling. One common grease complaint is simply too little grease, so if your old bearing had more, or a grease for a particular temperature range, write that in the inquiry and we will confirm what we can supply.

Deep groove ball bearings are tested on vibration and noise instruments and shipped at Z3V3 as standard. Before shipment each batch is checked for rotation smoothness, dimensions, grease fill, rust and appearance. Boxes show the model, grade and brand, and rings are marked with your authorised brand, our factory brand or left neutral, as you require. If you have an OEM part number in place of 6203, send it and we will confirm the standard model before quoting.

Neighbouring sizes

Model	Bore (mm)	OD (mm)	Width (mm)	Note
6202	15	35	11	One size down
6203	17	40	12	This page
6204	20	47	14	One size up
6003	17	35	10	Same bore, lighter
16003	17	35	8	Same bore, thin section
6303	17	47	14	Same bore, heavier

The complete 6200 series runs from 6200 to 6220, and the 6200 series cross-reference shows how other makers write the seal and shield suffixes. Send the model, suffix, clearance and quantity to sales@fuli-bearings.com or WhatsApp +86 152 6352 1305.

Sources

1. SKF Rolling bearings catalogue (PUB BU/P1 17000/1 EN) (SKF)
2. ISO 15:2017 Rolling bearings - Radial bearings - Boundary dimensions, general plan (preview) (ISO via iTeh Standards)
3. Deep Groove Ball Bearings (product page) (NSK)
4. NTN Ball and Roller Bearings catalog 2203-E, Section 8: Bearing internal clearance and preload (NTN)
5. Fits and Internal Clearance (ABC of bearings) (NSK)