Shaft seals

A 25 × 47 × 7 oil seal wants a H8 bore at least 7.3 mm deep, and an h11 shaft ground to Ra 0.2 to 0.8 µm with no lead, at least 45 HRC, with a lead-in chamfer 2.5 mm across. Enter the seal’s shaft, bore and width, or pick a standard size, for the housing bore and the shaft it runs on.

The seal is drawn in its bore in section, the main lip facing the fluid it keeps in.

Type AS: rubber-covered od, spring-loaded lip and a dust lip. Also Trelleborg TRE, Freudenberg BASL, NOK TC.

Housing bore: Ø 47 H8
Shaft: Ø 25 h11

Bore depth, at least
Bore finish: Ra 1.6 – 3.2µm
Bore lead-in chamfer: about 20°
Shaft finish: Ra 0.2 – 0.8µm
Shaft hardness, at least: 45HRC
Shaft lead-in chamfer, 15° – 25°
Or a rounded end, r at least: 1mm
Pressure, standard seal: up to 0.05MPa (0.5 bar)

How it’s calculated

d1	D	b
10	22	7
10	26	7
12	22	7
12	24	7
12	30	7
14	24	7
14	30	7
15	26	7
15	30	7
15	35	7
16	30	7
18	30	7
18	35	7
20	30	7
20	35	7
20	40	7
22	35	7
22	40	7
25	35	7
25	40	7
25	47	7
25	52	7
28	40	7
28	47	7
28	52	7
30	40	7
30	42	7
30	47	7
30	52	7
32	45	7
32	47	7
32	52	7
35	47	7
35	50	7
35	50	8
35	52	7
35	55	8
38	55	7
38	62	7
40	52	7
40	55	7
40	55	8
40	62	7
42	55	8
42	62	8
45	60	8
45	62	8
45	65	8
48	62	8
50	65	8
50	68	8
50	72	8
55	70	8
55	72	8
55	80	8
60	75	8
60	80	8
60	85	8
65	85	10
65	90	10
70	90	10
70	95	10
75	95	10
75	100	10
80	100	10
80	110	10
85	110	12
85	120	12
90	110	12
90	120	12
95	120	12
95	125	12
100	120	12
100	125	12
100	130	12

Shaft d1 over – incl.	d1 − d2 min
0 – 10	1.5
10 – 20	2
20 – 30	2.5
30 – 40	3
40 – 50	3.5
50 – 70	4
70 – 95	4.5
95 – 130	5.5
130 – 240	7
240 – 480	11

Why does the shaft matter more than the seal?

The lip runs on the shaft, so its finish decides how long the seal lasts. Grinding marks that spiral along the shaft can pump the fluid out past the lip, which is why every maker asks for a plunge ground shaft with no lead. A shaft that is too smooth starves the lip of lubricant and one that is too rough wears it. The makers agree on most of it, and where they differ, on the bore chamfer angle, the bore depth and the minimum hardness, the page gives each maker’s figure.

d1	D	b
10	22	7
10	26	7
12	22	7
12	24	7
12	30	7
14	24	7
14	30	7
15	26	7
15	30	7
15	35	7
16	30	7
18	30	7
18	35	7
20	30	7
20	35	7
20	40	7
22	35	7
22	40	7
25	35	7
25	40	7
25	47	7
25	52	7
28	40	7
28	47	7
28	52	7
30	40	7
30	42	7
30	47	7
30	52	7
32	45	7
32	47	7
32	52	7
35	47	7
35	50	7
35	50	8
35	52	7
35	55	8
38	55	7
38	62	7
40	52	7
40	55	7
40	55	8
40	62	7
42	55	8
42	62	8
45	60	8
45	62	8
45	65	8
48	62	8
50	65	8
50	68	8
50	72	8
55	70	8
55	72	8
55	80	8
60	75	8
60	80	8
60	85	8
65	85	10
65	90	10
70	90	10
70	95	10
75	95	10
75	100	10
80	100	10
80	110	10
85	110	12
85	120	12
90	110	12
90	120	12
95	120	12
95	125	12
100	120	12
100	125	12
100	130	12

d1	D	b
10	22	7
10	26	7
12	22	7
12	24	7
12	30	7
14	24	7
14	30	7
15	26	7
15	30	7
15	35	7
16	30	7
18	30	7
18	35	7
20	30	7
20	35	7
20	40	7
22	35	7
22	40	7
25	35	7
25	40	7
25	47	7
25	52	7
28	40	7
28	47	7
28	52	7
30	40	7
30	42	7
30	47	7
30	52	7
32	45	7
32	47	7
32	52	7
35	47	7
35	50	7
35	50	8
35	52	7
35	55	8
38	55	7
38	62	7
40	52	7
40	55	7
40	55	8
40	62	7
42	55	8
42	62	8
45	60	8
45	62	8
45	65	8
48	62	8
50	65	8
50	68	8
50	72	8
55	70	8
55	72	8
55	80	8
60	75	8
60	80	8
60	85	8
65	85	10
65	90	10
70	90	10
70	95	10
75	95	10
75	100	10
80	100	10
80	110	10
85	110	12
85	120	12
90	110	12
90	120	12
95	120	12
95	125	12
100	120	12
100	125	12
100	130	12

d1	D	b
10	22	7
10	26	7
12	22	7
12	24	7
12	30	7
14	24	7
14	30	7
15	26	7
15	30	7
15	35	7
16	30	7
18	30	7
18	35	7
20	30	7
20	35	7
20	40	7
22	35	7
22	40	7
25	35	7
25	40	7
25	47	7
25	52	7
28	40	7
28	47	7
28	52	7
30	40	7
30	42	7
30	47	7
30	52	7
32	45	7
32	47	7
32	52	7
35	47	7
35	50	7
35	50	8
35	52	7
35	55	8
38	55	7
38	62	7
40	52	7
40	55	7
40	55	8
40	62	7
42	55	8
42	62	8
45	60	8
45	62	8
45	65	8
48	62	8
50	65	8
50	68	8
50	72	8
55	70	8
55	72	8
55	80	8
60	75	8
60	80	8
60	85	8
65	85	10
65	90	10
70	90	10
70	95	10
75	95	10
75	100	10
80	100	10
80	110	10
85	110	12
85	120	12
90	110	12
90	120	12
95	120	12
95	125	12
100	120	12
100	125	12
100	130	12