Lock Washer
Safety Nut
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Bob-Lock
Safety Nut |
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Features |
The object of Best on Bolt
is to provide a secure lock against loosening. The well-tried Bob-Lock
wedge lock washers from Best-On-Bolt fulfil all usual demands on a vibration-resistant
locking element. The latest development from Best on Bolt,
based on the wedge lock principle, is a high performance Safety Nut, which
meets the following requirements:
- The Bob-Lock Safety Nut secures the bolt with highest reliability
without any damage to the surface of the work piece respectively to
the bolt and the nut as in the case with tooth or wedge lock washers.
- The bolt is secured with highest reliability independent from any
settlement in the bolted joint.
- The lock is performed solely on the nut and there is no action on
the bolt head. This feature facilitates considerably the assembling
and enables it to be used with the stud bolts.
- It is possible to add free spinning washers at the bolt head and
the nut which serves as a surface protection and better pressure distribution
without cancelling the effectiveness of the securing facility. This
loss of security happens to all other braced locking washers.
- We use the torque values of the bolt manufacturers to achieve the
necessary clamp load without restriction because our design has no
rough surface and therefore no correction for increased friction has
to be taken into consideration as in the case for tooth washers and
wedge lock washers.
- Also of importance is that the Bob-Lock Safety Nut can be reused
a high number of times without wear or loss of effectiveness.
- Another feature is that the thread of bolt and nut can be lubricated
with no reduction in the locking effectiveness.
- The Bob-Lock Safety Nut requires no change whatsoever to the bolt.
- The new securing facility can even be mounted behind the assembled
standard nut.
- The width across flats and the required wrench size are the same
as is for the standard nut.
- Most important is that the assembly of the Bob-Lock Safety Nut is
easy and fail safe.
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Pictures |
Pic 1-2: Components of the safety nut
Pic 3-4: Washer-packet and assembled safety nut
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Drawings |
Fig. 1: Sectional drawing / exploded drawing
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Fig. 2: View of the assembled nut
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Fig. 3: Side view of the washer-packet
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Fig. 4: View from above/below on the middle washer
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Fig. 5: Outer washer - view from below
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Fig. 6: Outer washer - view from above
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Fig. 7: Non-operative bolted joint
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Fig. 8: Bolted joint under dynamic load
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Fig. 9: Sectional drawing of a washer-packet with cover
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Fig. 10: Version with cover cap
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Function
Description of the Bob-Lock Safety Nut |
The new Bob-Lock Safety Nut for the securing of bolted joints against
loosening consists of a 3-disc pack, set into a nut, and a short threaded
pin as a lock bolt, which presses the 3-disc pack to the shaft’s
end of the secured bolt. The three discs are wedge lock washers, which
are comprised by a central ring. The central wedge lock washer has tabs,
which are situated into corresponding grooves of the nut. The grooves
are not end-to-end, so the 3-disc pack cannot fall through.
The nut can be tightened with the original torque value and only afterwards
follows the contact between the outer washer and the shaft’s end,
so no damage of the work piece and no loss of clamp load due to raised
friction results. The cams of the wedge lock washers have an angle,
which is higher than the angle of the pitch. When the nut and/or the
lock bolt starts loosening, two washers distort against each other and
as a result of the wedge design, they shift axial and so create a self-locking
effect. The security effect of the safety nut concerns both, the nut
and the screw, without the need of any additional measure on the bolt
head and it functions also on a free spinning washer.
The Bob-Lock Safety Nut has the same radial measurements as a standard
nut and includes in its height a tolerance sector for various screw
lengths (5-10 mm, depending on the standard lengths of the bolts). Present
bolts can retain, and the safety nut can also be mounted behind a not
disassembled standard nut.
The Bob-Lock Safety Nut will be delivered as a one-piece element with
pre-assembled 3-disc pack and lock bolt. The standard quality of the
nut is 10, the coating is Delta Protekt. If desired, a coloured cover
cap made of plastics can be added as a security signal.
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