Machine Design
A hollow saddle key is

Provided in pairs at right angles and each key is to withstand torsion in one direction only
A taper key which fits in a key way of the hub and is flat on the shaft
A taper key which fits in a key way of the hub and the bottom of the key is shaped to fit the curved surface of the shaft
A taper key which fits half in the key way of hub and half in the key way of shaft

ANSWER DOWNLOAD EXAMIANS APP

Machine Design
Castle nut is a locking device in which

Through slots are made at top and a cotter pin is passed through these and a hole in the bolt, and cotter pin spitted and bent in reverse direction at other end
A slot is cut partly is 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

ANSWER DOWNLOAD EXAMIANS APP
MORE MCQ ON Machine Design