Machine Design
In the calculation of induced shear stress in helical springs, the Wahl's stress factor is used to take care of

Combined effect of transverse shear stress and bending stress in the wire
Combined effect of transverse shear stress and curvature of wire
Combined effect of torsional shear stress and transverse shear stress in the wire
Combined effect of bending stress and curvature of the wire

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Machine Design
In oilness bearings

The oil film is maintained by supplying oil under pressure
The oil film pressure is generated only by the rotation of the journal
Do not require external supply of lubricant
Grease required to be applied after some intervals

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Machine Design
Jam nut is a locking device in which

A slot is cut partly in middle of nut and then slot reduced by tightening a screw
One smaller nut is tightened over main nut and main nut tightened against smaller one by loosening, creating friction jamming
A hard fibre or nylon cotter is recessed in the nut and becomes threaded as the nut is screwed on the bolt causing a tight grip
Through slots are made at top and a cotter pin is passed through these and a hole in the bolt, and cotter spitted and bent in reverse direction at other end

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