| Washers come in a wide variety
of designs and within those individual designs are a range of
materials, dimensional variations and finishes. |
| Many can be used either under
the head of the fastener, bolt or screw, or under the nut. |
| Many can be encapsulated as an
assembly on a screw or bolt, or occasionally with a nut; these
products are called SEMS. |
| Most washer sizes will be
designated by the diameter (size) of the fastener with which
they are to be used. |
 |
Basic Washers are employed
to:
- spread the clamp load over a larger surface area
- cover an oversize or elongated hole
- reduce the friction of the rotated component
- protect the work piece surface from damage by the rotated component
- provide a locking or vibration resistant function |
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|
Specialist washers have
been designed to perform particular functions in particular
types of applications. These may be locking, load spreading,
decorative, tension indicating, sealing, or a combination of
these functions. Some of the most common are shown in the
charts following. |
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|
SKETCH |
TITLE |
COMMENTS |
 |
FLAT (Black, Bright) |
Common general
purpose basic washer, can come in various dimensional standards,
quality levels, materials, hardness grades and finishes.
Could also be available square.
Often used in conjunction with a split spring washer. |
 |
SPLIT SPRING |
Common locking
washer, will come in a variety of thicknesses and sectional
ratios.
Available in various materials throughout a wide size range.
Used to resist vibration loosening.
Will damage surfaces it contacts. |
 |
BELLEVILLE WASHER
(Conical) |
For use in high
vibration applications where tension must be maintained if some
loosening occurs.
Can be used in stacks or series to increase the axial load or to
increase the possible deflection length. |
 |
INTERNAL TOOTH
LOCK WASHER
(Shake Proof) |
Used with pan or
cheese head machine screws to resist vibration.
Minimal damage to surface. |
 |
EXTERNAL TOOTH
LOCK WASHER
(Shake Proof) |
Same as above
except slightly more damaging to surface.
Also available in countersunk version. |
 |
WAVE |
Can be available
as full circle or split.
Is used in place of spring washers where surface damage is to be
avoided.
Also used where some pressure is required on a free element of
an assembly.
Usually confined to small diameters. Similar products are
crinkle washers. |
 |
CURVED |
Generally
confined to light applications similar to above, where only very
light pressure is required. |
 |
SCREW CUP
(Cup) |
Used under a
countersunk screw where a decorative or appealing finish is
required; eg. Automotive door trims.
Normally would be nickel or chrome plated, or in stainless
material. |
 |
NEOPRENE
(Neo) |
A rubber type
material used in roofing screw applications under washer head
screws with sealing washer recess.
Designed to create a waterproof seal between the screw and
sheeting material.
Can also be bonded to aluminium or stainless washers.
|
 |
CYCLONE WASHERS |
Various styles to
suit the range of roofing profiles.
Bonded with neoprene, these washers spread the load over a large
area of roof sheeting, reinforcing the sheeting against lifting
over the screw heads in cyclonic conditions. |
 |
STRUCTURAL |
A hardened steel
washer used in conjunction with structural bolts in heavy
construction applications. The washer reduces galling between
the tightened surfaces and spreads the load.
The three external tabs identify it as a structural washer. |
 |
LOAD INDICATING
WASHER (Coronet) |
Used in the
structural industry to provided evidence that the required
tension has been achieved.
The raised protrusions will crush in relation to the load
applied, providing a permanent witness that required tension was
achieved. |
