Technical Specification | Luoyang Mingzhen Bearing Steel Ball Co., Ltd.

ISO3290-1:2008 / GB/T308.1-2013 Rolling bearings — Balls - Part 1: Steel balls
Grade	Variation of ball diameter VDws(≤) (μm)	Deviation from spherical form ∆RSw(≤) (μm)	Surface roughness Ra(≤) (μm)	Variation of ball lot diameter VDwL(≤) (μm)	Ball gauge interval (μm)	Preferred ball gauges (μm)
G 3	0.08	0.08	0.01	0.13	0.5	-5 ~ +5
G 5	0.13	0.13	0.014	0.25	1	-5 ~ +5
G 10	0.25	0.25	0.02	0.5	1	-9 ~ +9
G 16	0.4	0.4	0.025	0.8	2	-10 ~ +10
G 20	0.5	0.5	0.032	1	2	-10 ~ +10
G 24	0.6	0.6	0.04	1.2	2	-12 ~ +12
G 28	0.7	0.7	0.05	1.4	2	-12 ~ +12
G 40	1	1	0.06	2	4	-16 ~ +16
G 60	1.5	1.5	0.08	3	6	-18 ~ +18
G 100	2.5	2.5	0.1	5	10	-40 ~ +40
G 200	5	5	0.15	10	15	-60 ~ +60

JB/T 5301-2007 Rolling bearing — Carbon steel balls
Grade	Variation of ball diameter VDws(≤) (μm)	Deviation from spherical form ∆RSw(≤) (μm)	Surface roughness Ra(≤) (μm)	Variation of ball lot diameter VDwL(≤) (μm)	Ball gauge interval (μm)	Preferred ball gauges (μm)
G 3	0.08	0.08	0.01	0.13	0.5	-5 ~ +5
G 5	0.13	0.13	0.014	0.25	1	-5 ~ +5
G 10	0.25	0.25	0.02	0.5	1	-9 ~ +9
G 16	0.4	0.4	0.025	0.8	2	-10 ~ +10
G 20	0.5	0.5	0.032	1	2	-10 ~ +10
G 24	0.6	0.6	0.04	1.2	2	-12 ~ +12
G 28	0.7	0.7	0.05	1.4	2	-12 ~ +12
G 40	1	1	0.06	2	4	-16 ~ +16
G 60	1.5	1.5	0.08	3	6	-18 ~ +18
G 100	2.5	2.5	0.1	5	10	-40 ~ +40
G 200	5	5	0.15	10	15	-60 ~ +60

Hardness of completed steel balls
Nominal ball diameter D_w mm	Chrome steel balls HRC	Carbon steel balls HRC	high-carbon chromium bearing stainless steel balls HRC	high-temperature bearing steel balls HRC
0 ~ 30	61 ~ 66	≥ 60	≥ 58	61 ~ 66
30 ~ 50	60 ~ 65	≥ 60	≥ 58	61 ~ 66
≥ 50	58 ~ 64	≥ 60	≥ 58	61 ~ 66

Preferred nominal ball diameters
Nominal ball diameter D_w mm	Corresponding inch size (reference) in	Nominal ball diameter D_w mm	Corresponding inch size (reference) in	Nominal ball diameter D_w mm	Corresponding inch size (reference) in
0.3		9.525	3/8	30.1625	1 3/16
0.39688	1/64	9.92188	25/64	31.75	1 1/4
0.4		10		32
0.5		10.31875	13/32	33
0.508	0.02	10.5		33.3375	1 5/16

0.6		11		34
0.635	0.025	11.1125	7/16	34.925	1 3/8
0.68		11.5		35
0.7		11.50938	29/64	36
0.79375	1/32	11.90625	15/32	36.5125	1 7/16

0.8		12		38
1		12.30312	31/64	38.1	1 1/2
1.19062	3/64	12.5		39.6875	1 9/16
1.2		12.7	1/2	40
1.5		13		41.275	1 5/8

1.5875	1/16	13.49375	17/32	42.8625	1 11/16
1.98438	5/64	14		44.45	1 3/4
2		14.2875	9/16	45
2.38125	3/32	15		46.0375	1 13/16
2.5		15.08125	19/32	47.625	1 7/8

2.77812	7/64	15.875	5/8	49.2125	1 15/16
3		16		50
3.175	1/8	16.66875	21/32	50.8	2
3.5		17		53.975	2 1/8
3.57188	9/64	17.4625	11/16	55

3.96875	5/32	18		57.15	2 1/4
4		18.25625	23/32	60
4.36562	11/64	19		60.325	2 3/8
4.5		19.05	3/4	63.5	2 1/2
4.7625	3/16	19.84375	25/32	65

5		20		66.675	2 5/8
5.15938	13/64	20.5		69.85	2 3/4
5.5		20.6375	13/16	70
5.55625	7/32	21		73.025	2 7/8
5.95312	15/64	21.43125	27/32	75

6		22		76.2	3
6.35	1/4	22.225	7/8	79.375	3 1/8
6.5		22.5		80
6.74688	17/64	23		82.55	3 1/4
7		23.01875	29/32	85

7.14375	9/32	23.8125	15/16	85.725	3 3/8
7.5		24		88.9	3 1/2
7.54062	19/64	24.60625	31/32	90
7.9375	5/16	25		92.075	3 5/8
8		25.4	25.4	95

8.33438	21/64	26		95.25	3 3/4
8.5		26.19375	1 1/32	98.425	3 7/8
8.73125	11/32	26.9875	1 1/16	100
9		28		101.6	4
9.12812	23/64	28.575	1 1/8	104.775	4 1/8

9.5	30