General Description
This type of diaphragm has a rectangular bead molded inside the cylinder wall. This design requires the smallest hardware diameter of any diaphragm type. Since clamping and sealing in this style is against the inside wall of the cylinder, the stroke capability is restricted to the lower half of the diaphragm. Type OB Diaphragm

Dimensions and Tolerances
Type OB Figure 1

Inches mm Inches mm Inches mm Inches mm
Cylinder Diameter
1.00-2.50
25-64
2.51-4.00
64-102
4.01-8.00
102-205
8.01 & up
205 & up
Height
See available sizes table
Cylinder Diameter
Tolerances on Cylinder Diameter and Piston Diameter are ± 0.010 per inch (0.254 mm) of diameter but the tolerance will be no less than ± 0.010 (0.254 mm) or greater than ± 0.060 (1.52 mm)
Piston Diameter
Head & Flange Thickness
.017 ± .004
0.43 ± 0.10
.024 ± .004
0.61 ± 0.10
.035 ± .005
0.89 ± 0.13
.045 ± .007
1.14 ± 0.18
Wall Gauge
.017 ± .003
0.43 ± 0.08
.024 ± .004
0.61 ± 0.10
.035 ± .005
0.89 ± 0.13
.045 ± .007
1.14 ± 0.18
Flash Projection
.025 Max.
0.64 Max.
.035 Max.
0.89 Max.
.040 Max.
1.02 Max.
.056 Max.
1.42 Max.
Flash Thickness
.025 Max.
0.64 Max.
.035 Max.
0.89 Max.
.040 Max.
1.02 Max.
.056 Max.
1.42 Max.
Flange Radius
.031
0.79
.047
1.19
.063
1.60
.063
1.60
Bead Width
.080 ± .003
2.03 ± 0.08
.100 ± .003
2.51 ± 0.08
.120 ± .003
3.05 ± 0.08
.160 ± .003
4.06 ± 0.08
Bead Height
.150 ± .005
3.81 ± 0.13
.200 ± .005
5.08 ± 0.13
.260 ± .005
6.60 ± 0.13
.300 ± .007
7.62 ± 0.18


Hardware Recommendations

Stamped Retainer Plate Sealing Via Axial Compression
Cast Machined Retainer Plate Sealing Via Radial Compression
Type OB Figure 2 Type OB Figure 3


Cylinder Diameter
Bead Groove Width = W
Bead Groove Height = H
Lip Radius = R1
Piston Corner Radius = R2
Lip Clearance = C
(Inches) (mm) (Inches) (mm) (Inches) (mm) (Inches) (mm) (Inches) (mm)
Sidewall Thickness + .003

1.00-2.50
25-64
.080
2.03
1.50
3.81
.030
0.76
.063
1.60

2.51-4.00
64-102
.100
2.45
.200
5.08
.040
1.02
.094
2.39

4.01-8.00
102-205
.120
3.05
.260
6.60
.050
1.27
.125
3.18

8.01 and up
205 and up
.160
4.06
.300
7.62
.060
1.52
.188
4.78


Available Sizes
Dia•Com
Part No,		 Cylinder
Diameter
 Piston
Diameter
 Height
 Gauge
Approx.
 Convolution
Width
 Effective
Pressure
Area
 Maximum
Half-Stroke
(Inches) (mm) (Inches) (mm) (Inches) (mm) (Inches) (mm) (Inches) (mm) (Inches) * (Inches) (mm)

OB-250-178
2.50
64
2.13
54
1.78
45
.035
0.89
.185
4.7
4.21
27.1
1.39
35.3

OB-250-225
2.50
64
2.13
54
2.25
57
.035
0.89
.185
4.7
4.21
27.1
1.86
47.2

OB-250-258
2.50
64
2.06
52
2.58
66
.035
0.89
.220
5.6
4.08
26.3
2.14
54.4

OB-300-284
3.00
76
2.56
65
2.84
72
.035
0.89
.220
5.6
6.07
39.1
2.39
60.7

OB-300-284
3.00
76
2.63
67
2.84
72
.035
0.89
.185
4.7
6.22
40.1
2.45
62.2

OB-306-338
3.06
78
2.63
67
3.38
86
.035
0.89
.215
5.5
6.35
41.0
2.95
74.9

OB-362-340
3.62
92
3.12
79
3.40
86
.035
0.89
.250
6.4
8.92
57.5
2.33
59.2

OB-362-351
3.62
92
3.12
79
3.51
89
.035
0.89
.250
6.4
8.92
57.5
2.44
62.0

OB-363-406
3.62
92
3.12
79
4.06
103
.035
0.89
.250
6.4
8.92
57.5
3.09
78.5

OB-388-406
3.88
99
3.38
86
4.06
103
.035
0.89
.250
6.4
10.34
66.7
3.09
78.5

OB-388-413
3.88
99
3.33
85
4.13
105
.035
0.89
.275
7.0
10.20
65.8
3.12
79.2

OB-416-195
4.16
106
3.66
93
1.95
50
.035
0.89
.250
6.4
12.00
77.4
0.95
24.1

OB-416-353
4.16
106
3.66
93
3.53
90
.035
0.89
.250
6.4
12.00
77.4
2.53
64.3

OB-416-481
4.16
106
3.66
93
4.81
122
.035
0.89
.250
6.4
12.00
77.4
3.81
96.8

OB-475-374
4.75
121
4.25
108
3.74
95
.035
0.89
.250
6.4
15.90
102.6
2.61
66.3

OB-475-541
4.75
121
4.25
108
5.41
137
.035
0.89
.250
6.4
15.90
102.6
4.28
108.7

OB-700-414
7.00
178
6.50
165
4.14
105
.040
1.02
.250
6.4
35.77
230.8
3.01
76.5

*Metric effective pressure area shown in square centimeters.