tf-22This unique Sems fastener features an integral, free-spinning, Square Cone® (Square Dome) washer. With two distinct configurations, this dual action spring washer has two separate load deflection rates. The configurations act in unison to provide a reliable low-torque, controlled tension fastener. The Square Cone® (Square Dome) Sems assembly provides a higher retained clamp load and improved compensation for thermal cycling and vibration. This fastener is capable of accepting a high tension load while maintaining alive spring action and generates a constant load, even with variations in installation torques. By increasing the acceptable driving torque range, it enhances flexibility in component design.

The Square Cone® (Square Dome) washer’s long deflection period and two-stage loading contribute to better control during installation, improve tool bit life and reduce operator fatigue. (See Fig. 1) Load is directed toward the outer diameter of the washer, making the fastener ideal for clamping fragile materials and preventing stress cracking problems around clearance holes.

Approximate Tightening Torques For Machine Screw Sems With Tooth Lock Washers Or Square Cone® (Square Dome) Washers

Customary Dimensions Expressed As Inch-Pounds – Grade 2 Screw Material
SIZE 4-40 6-32 8-32 10-32 7309
TORQUE 5 11 21 35 75

Metric Dimensions Expressed In Newton-Meters (N.m) Property Class 5.8 Screw Material

SIZE M2.0 M3.0 M3.5 M4.0 M5.0 M6.0
TORQUE 0.3 0.6 1.2 2.4 4 7.5

Slotted Indented Hex Head, Torx® And Phillips Pan Head

Specifications For Inch Sizes

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Inch Sizes 

SIZE A
Hex		 B1
Hex		 B2
Pan		 C1
Hex		 C2
Pan		 PHILLIPS DRIVER TORX
DRIVER		 D
Wash		 H
Wash		 T
Wash		 E
Hex		 F
Hex
4-40 187
.181		 .202
MIN.		 .219
.205		 .096
.084		 .080
.070		 No. 1 T10 .250
.244		 .039
.021		 0.015 .039
.031		 .054
.044
6-32 .250
.244		 .272
MIN.		 .270
.256		 .096
.084		 .097
.087		 No. 2 T15 .320
.307		 .061
.039		 0.025 .048
.038		 .054
.044
8-32 .250
.244		 .272
MIN.		 .322
.306		 .120
.105		 .115
.105		 No. 2 T20 .383
.370		 .073
.050		 0.03 .054
.045		 .066
.052
10-32 312
.305		 .340
MIN.		 .373
.357		 .141
.126		 .133
.122		 No. 1 T25 .446
.433		 .075
.051		 0.032 .060
.050		 .080
.066
1/4-20 .375
.367		 .409
MIN.		 .492
.473		 .206
.140		 .175
.162		 No. 3 T30 .508
.495		 .088
.064		 0.039 .075
.064		 .101
.083

Note: Square Cone® is a Registered Trademark of ITW.
Semblex Square Dome® are registered trademarks of Semblex Corp.
Torx® is a Registered Trademark of Camcar-Textron Incorporated.
* Slotted Hex Optional
WCL also stocks Square Dome imported Sems

Slotted Indented Hex Head, Torx® And Phillips Pan Head

Specifications For Metric Sizes

SIZE A
Hex		 B1
Hex		 B2
Pan		 C1
Hex		 C2
Pan		 PHILLIPS DRIVER TORX
DRIVER		 D
Wash		 H
Wash		 T
Wash		 E
Hex		 F
Hex
M2.5X0.45 4.70
5.00		 1.90
2.10		 No. 1 5.08 – 5.35
6.20 – 6.35		 1.00 0.40 or 0.45
0.50
M3X0.5 5.00
4.82		 5.40
MIN.		 5.60
5.30		 2.30
2.00		 2.40
2.20		 No. 1 T10 7.82
7.52		 1.55
0.99		 0.64 1.00
0.80		 1.17
0.84
M3.5X0.6 5.50
5.32		 5.96
MIN.		 7.00
6.60		 2.60
2.30		 2.60
2.30		 No. 2 T15 7.82
7.52		 1.55
0.99		 0.64 1.20
1.00		 1.47
1.17
M4X0.7 7.00
6.78		 7.59
MIN.		 8.00
7.60		 3.00
2.60		 3.10
2.80		 No. 2 T20 8.46
8.20		 1.65
1.32		 0.76 1.50
1.20		 1.75
1.40
M5X0.8 8.00
7.78		 8.74
MIN.		 9.50
9.10		 3.80
3.30		 3.70
3.40		 No. 2 T25 9.73
9.47		 2.59
1.65		 0.94 1.59
1.20		 2.18
1.78
M6X1.0 10.00
9.78		 10.95
MIN.		 12.00
11.50		 4.70
4.10		 4.60
4.30		 No. 3 T30 12.90
12.57		 2.24
1.63		 0.99 1.90
1.60		 2.36
1.91

Square Cone® is a Registered Trademark of ITW.
Semblex Square Dome® are registered trademarks of Semblex Corp.
Torx® is a Registered Trademark of Camcar-Textron
* Slotted Hex Optional

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A = Across Flats
B1 = Across Corners
B2 = Pan Head O.D.
C1 = Hex Head Height
C2 = Pan Head Height
D = Washer Diameter
H = Overall Washer Height
T = Washer Material Thickness
E = Slot Width
F = Slot Depth
Other head styles and drives may be specified