Bolt
Locking
Overview of Safety- & Load Washers
Introduction to Schnorr® Safety Washers
Often disc springs are considered for use as safety washers for bolted connections, for preloading- or preventing loosening of the connection. The economic viability is not great and standard sizes of disc springs do not match bolt or screw sizes.
Thus Schnorr®developed a reliable and economically viable bolt locking system based on the principle of the disc spring. These patented safety washers are in the form of a disc spring which is serrated on both sides with trapezoidal cross section.
The diameters match screw dimensions: The outer diameter matches the head diameter of the pan screw and hexagon head cap screws. Thus the safety washers can be used with most screw- or bolt types, one exception being counter-sunk screws.
Introduction to Schnorr® Load Washers
A “load washer” is in the form of a disc spring achieving its locking effect solely by means of the frictional connection. Load washers are intended for use in compensating for loosening of the screwed connection, by maintaining sufficiently high pretension in the connection with spring force.
Load washers are especially suitable for primarily axially loaded, short bolts. They provide no effective security against unscrewing caused by alternating lateral loading.
Load washers were developed for high strength bolts. High loads require large cross sections, which is why the outside diameter of a load washer is larger than that of a safety washer.
As a highly progressive load increase occurs at the end of the spring deflection, when the load washer is flattened, the load has been indicated as double the calculated value. Tests have shown that these values are comparable with the measured values.
Advantages of Schnorr® Safety Washers
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High resistance to vibration due to positive locking of serrations.
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The closed ring form results in a high degree of pre tensioning, while avoiding burstopen effect.
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Concentric application of force eliminates bending of the bolts.
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The serration design prevents friction and damage when tightening.
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High safety against loss of pretension force and loosening.
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Can be made available in a variety of materials and finishes.
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Development and design of the washers take place on the basis of the screw geometrics, tightening torque as well as the constructive circumstances.
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Also applicable for clearance holes (safety washer is necessary on both sides).
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Applicable for elongated holes (using type VS).
Advantages of Schnorr® Load Washers
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High axial load.
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Optimum compensation for setting in the joint.
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Reduction of the dynamic loading of the screw.
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Uniform concentric loading eliminates bending of the bolt.
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Greater safety with high degree of spring action.
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Suitable for captive fitting on a wide range of bolts (combi bolts).
Standards
Schnorr® load washers conform to DIN 6796.
Types of Schnorr® Safety washers
Available are 2 types of safety washers: “S” and “VS”
“S”
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normal duty
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Screw sizes M1.6 to M36
“VS”
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reinforced safety washer
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Is thicker
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Achieves higher pre-tensioning loads
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Screw sizes M5 to M30
Correct use of Schnorr® Safety washers: The Original SCHNORR® Safety Washer is only able to obtain its full effectiveness as a bolt locking device if it is used correctly.
Schnorr® HS-Washers
In principle, the HS washer is a load washer with a smaller outer diameter than those according to DIN 6796.
The slightly curved form provides a progressively increasing characteristic curve, which makes it possible to achieve the same load as the load washers according to DIN 6796.
HS –Washers are primarily used when there is insufficient space available to use the standard load washers.
