Grade Info

One of the greatest challenges in manufacturing carbon brushes is supplying a grade that will maximize performance for the manner in which the motor or generator is operating. Consideration must be given to the actual running loads, duty cycle, voltage, peripheral speeds, and the environment.

Helwig Carbon’s technical staff is experienced in selecting the proper grade for your application. Choosing the wrong material could cause considerable damage to your equipment. However, overall, grades have been held more accountable for brush performance than is warranted. While selecting the proper grade is crucial, other factors often have a greater effect on brush performance.

Many of the grades used today are derived through variations in raw materials, molding pressure, temperature, duration of the baking process, and after-treatments. All brush grades fall into five categories:

Carbon Graphite
Graphite
Electrographite
Copper Graphite
Silver Graphite

Each material is designed and developed to perform under certain operating conditions. A best grade for each application is offered, although, several grades with similar characteristics may offer satisfactory performance.

CARBON GRAPHITE

Carbon graphite grades were developed early in the history of motors and generators. These grades, therefore, are found most often on older equipment, particularly those with flush mica commutators. Carbon graphite offers cleaning action for use at slow speeds, low-current densities and medium to low voltages.

ELECTROGRAPHITE

Electrographite is the most common grade used on modern equipment. With excellent performance at high voltages, high-current densities and high speeds, wide ranges of characteristics exist within this category. Most electrographite grades are capable of handling overloads.

GRAPHITE

Graphite grades are used in special applications requiring low-friction characteristics. When brushes must operate at very low current densities or very high peripheral speeds, a graphite grade should be used.

COPPER GRAPHITE

Copper graphite has a material content of 15 – 95% copper or copper alloy. The added conductivity and lower voltage drop, allows metal graphite brushes to operate at very high current densities and low voltages.

SILVER GRAPHITE

Silver graphite has a material content of 8 – 95% silver. The added conductivity and lower voltage drop, allows metal graphite brushes to operate at very high current densities and low voltages.

electrographite, some of our grade information

Grade Data

Many of the grades used today are derived through variations in raw materials, molding pressure, temperature, duration of the baking process, and after-treatments. All brush grades fall into five categories and are represented by the tables below.

Key for Performance Characteristics

Voltage Drop VH 2.5 and Higher H 1.9 to <2.5 M 1.3 to <1.9 L 0.7 to <1.3V VL Less than 0.7V

Coefficient of Friction H 0.3 and Higher M 0.2 to < 0.3 L 0.1 to < 0.2 VL < 0.1

Film Code 1 Mild Abrasive = Light Film 2 No Cleaning - Filming 3 Film Forming Properties = Med - Dark Film

VDCFFilmRated Current

Voltage drop, coefficient of friction, film code, and rated current are performance characteristics. Values shown are based on tests under one standard set of conditions, and are for use in comparison between grades only. On any application, the values could vary due to differences in operating conditions.

Carbon Graphite

	Resistivity		Hardness	Strength					Rated Current
Grade	OHM-IN	µOHM-M	Shore	PSI	N/mm²	VD	CF	Film #	Amp/in²	Amp/cm²
H	0.0011	27	55	3000	20.7	M	M	1	40	6.2
H250	0.0008	20	60	6700	46.2	M	M	1	50	7.8
H357	0.0012	30	50	2800	19.3	M	M	1	55	8.5
H422	0.01	197	50	3600	27.9	H	L	1	60	9.3
H990	0.0027	67	70	4300	29.6	H	H	1	40	6.2
NH12	0.032	800	45	3025	20.1	H	L	1	55	8.5
NH16	0.02	500	25	2200	15.2	H	VL	1	55	8.5
NH4	0.0016	40	45	2500	17.2	M	L	1	50	7.8

Electrographite

	Resistivity		Hardness	Strength					Rated Current
Grade	OHM-IN	µOHM-M	Shore	PSI	N/mm²	VD	CF	Film #	Amp/in²	Amp/cm²
H22	0.00075	18	45	3000	25.6	M	L	2	70	10.9
H23	0.0015	37	70	4500	31.0	M	L	1	70	10.9
H24	0.0016	40	55	4100	26.2	M	L	2	80	12.4
H25	0.0012	30	65	5100	35.2	M	L	2	80	12.4
H27	0.0017	43	65	3900	26.9	H	VL	2	80	12.4
H28	0.0018	46	45	2600	17.9	M	VL	2	80	12.4
H3	0.00035	9	35	3500	24.1	M	VL	3	70	10.9
H34	0.0022	55	75	4400	30.3	H	L	2	80	12.4
H35	0.0022	55	50	2500	17.2	H	L	2	90	14.0
H36	0.0022	55	70	3300	22.8	H	VL	3	80	12.4
H37	0.0018	46	70	4400	30.3	H	VL	2	80	12.4
H38	0.0020	50	80	5400	37.2	M	VL	2	80	12.4
H39	0.0016	40	85	5400	37.2	H	VL	3	80	12.4
H41	0.0025	62	60	3000	20.7	H	VL	3	80	12.4
H43	0.0018	46	65	3700	25.5	M	L	2	90	14.0
H4399	0.0008	20	45	4000	27.6	H	L	3	80	12.4
H44	0.0017	42	85	5500	37.9	M	L	2	80	12.4
H4430	0.0022	55	48	2500	17.2	VH	L	3	80	12.4
H45	0.0025	62	55	3300	22.8	H	VL	3	80	12.4
H46	0.0010	25	25	1500	10.3	M	L	2	80	12.4
H47	0.0025	62	40	1500	10.3	H	L	2	80	12.4
H49	0.0025	62	45	2000	13.8	H	L	2	90	14.0
H50	0.0021	52	60	2900	20.0	M	L	2	90	14.0
H51	0.0022	55	60	3200	22.1	M	VL	2	80	12.4
H52	0.0022	55	60	2900	20.0	H	L	2	80	12.4
H55	0.0011	27	50	3975	27.4	M	L	3	75	11.6
H57	0.0021	52	50	2600	17.9	M	L	2	90	14.0
H580	0.00036	9	40	3700	25.5	M	L	1	90	14.0
H60	0.0021	53	75	5300	36	H	VL	3	80	12.4
H61	0.0006	15	30	1500	10.3	M	VL	2	75	11.6
H74	0.0030	75	55	1800	12.4	H	VL	3	80	12.4
H76	0.0030	75	65	2400	16.6	H	L	3	80	12.4
H77	0.0026	65	40	1800	12.4	H	VL	3	80	12.4
H82	0.0016	40	64	5000	34.4	M	L	2	80	12.4
H83	0.0017	42	70	3000	20.7	H	L	2	80	12.4
H84	0.0017	42	80	5500	37.9	H	L	2	80	12.4
HH	0.0006	15	40	3000	20.7	L	L	1	75	11.6

Graphite

	Resistivity		Hardness	Strength					Rated Current
Grade	OHM-IN	µOHM-M	Shore	PSI	N/mm²	VD	CF	Film #	Amp/in²	Amp/cm²
H552	0.0005	12	15	2000	13.8	L	L	2	60	9.3
H610	0.0008	20	20	4700	32.4	M	L	2	60	9.3
H619	0.0019	47	35	5500	37.9	VH	L	3	50	7.8
H621	0.07	1778	45	4500	31.0	VH	L	3	30	4.7
H646	0.01	250	30	5000	34.5	H	L	1	60	9.3
H649	0.0098	245	35	2600	17.9	H	L	2	65	10.1
H651	0.01	250	35	4300	29.6	H	L	2	55	8.5
H700	0.0004	10	25	2300	15.9	M	L	1	70	10.9
H702	0.001	25	15	700	4.8	M	M	1	60	9.3
H704	0.0006	15	15	1000	6.9	M	L	1	60	9.3
H7240	0.17	4250	55	4000	27.6	VH	M	2	25	3.9
K018	0.0007	17.7	40	3000	20.7	M	L	3	80	12.4
K094	0.06	1400	37	2100	15.9	VH	L	3	30	4.7
K174	0.008	200	27	1900	13.1	H	L	3	55	8.5
K194	0.003	76	25	4500	31.0	H	L	3	55	8.5
K214	0.035	889	37	3000	20.7	VH	L	2	55	8.5
K224	0.008	200	30	4000	27.6	VH	VL	2	55	8.5
K244	0.04	1020	35	2600	17.9	VH	L	2	40	6.2
K254	0.0009	30	40	3500	24.2	H	L	2	80	12.4
K294	0.025	530	35	2000	13.8	H	L	2	55	8.5
K384	0.013	330	25	2500	17.2	H	L	3	40	6.2

Copper Graphite

	Resistivity		Hardness	Strength					Rated Current
Grade	Ohm-in	µOhm-m	Shore	PSI	N/mm2	VD	CF	Film#	Amp/in2	Amp/cm2	Metal %
6H6	0.0005	9.7	35	2500	17.2	M	L	1	90	14	15
K275	0.0013	33.02	25	4000	27.5	M	L	2	80	12.4	27
6H1	0.00026	6.5	30	2700	18.6	M	L	1	100	15.5	30
H671	0.00025	6.3	50	6000	41.3	L	M	1	110	17.1	30
H4375	0.0003	6.6	23	3000	20.7	VL	L	2	110	17.1	30
K075	0.00026	6.6	25	4000	27.5	M	L	2	100	15.5	30
K165	0.0003	6.6	25	2500	17.2	L	L	2	110	17.1	35
6H2	0.00012	3	30	3700	25.5	L	L	1	110	17.1	40
H670	0.00018	4.5	40	5100	35.2	L	L	2	110	17.1	40
H4333	0.00015	3	23	4000	27.5	VL	L	2	130	20.2	40
K045	0.00011	2.8	25	4500	31	M	L	2	110	17.1	40
K175	0.00016	4.06	45	5000	34.4	L	L	2	110	17.1	40
K425	0.00019	4.82	25	5000	34.4	L	L	1	100	15.5	42
6H3	0.00006	1.8	25	3200	22.1	L	L	1	120	18.6	50
K085	0.0001	2.54	25	3300	22.8	M	L	1	125	19.3	50
K535	0.00004	1.02	25	5000	34.4	L	L	2	110	17.1	53
6H7	0.000033	0.64	25	3400	23.4	L	L	1	130	20.2	65
K176	0.000033	8.4	25	5000	34.4	L	L	1	130	20.2	65
K676	0.000014	0.35	25	5400	37.2	L	L	2	120	18.6	67
K736	0.000007	0.17	20	7500	51.6	L	L	1	130	20.2	73
6H8	0.000013	0.33	22	4500	31	VL	L	1	140	21.7	75
H682	0.000005	0.13	25	5100	35.2	L	VL	1	140	21.7	75
K136	0.000013	0.33	18	4800	33.1	VL	L	1	140	21.7	75
K216	0.00001	0.254	20	4000	27.5	L	L	1	140	21.7	77.5
K106	0.000004	0.1	8	6150	42.4	VL	L	1	150	23.3	85
K236	0.00002	0.5	20	9000	62.1	L	VL	1	150	23.3	85
H680	0.000003	0.08	18	9300	64.1	L	L	1	150	23.3	87
H692	0.000003	0.08	18	8800	60.7	VL	L	1	160	24.8	90
K076	0.000020	0.5	13	13000	89.6	VL	L	1	175	27.1	91
K086	0.000002	0.05	7	9000	62.1	VL	L	1	160	24.8	91
K286	0.000015	0.381	5	6000	41.3	L	L	1	160	24.8	94
H693	0.000002	0.06	20	11500	80	VL	L	1	175	27.1	95

Silver Graphite

Resistivity			Hardness / Strength					Rated Current
Grade	Ohn-in	µOhm-m	Shore	PSI	N/mm²	VD	CF	Film#	Amp/in²	Amp/cm²	Metal %
K297	0.0006	15.24	15	700	4.82	L	L	2	70	10.85	8
K047	0.0003	7.60	25	4500	31	L	L	2	100	15.50	29
K017	0.00005	1.27	20	3800	26.7	VL	L	2	140	21.70	50
K087	0.00006	1.52	25	3500	24.1	VL	L	3	130	20.10	50
K107	0.00003	0.76	25	6500	44.78	VL	L	1	140	20.15	60
K227	0.00004	1.01	25	3400	23.42	VL	L	1	140	20.15	60
K057	0.000008	0.16	20	5500	37.9	VL	L	1	160	24.80	77
K197	0.000004	0.10	15	5000	34.45	VL	L	1	170	26.35	80
K277	0.000002	0.05	10	8500	58.56	VL	L	1	180	27.90	88
K037	0.000002	0.05	6	6000	41.3	VL	L	1	200	31.00	91