It is usually used when a very long threaded member is desired A washer is a hardware component often used with threaded fasteners to ensure tightness of the mechanical joint. Thread Loosening and Thread Locking The greater the helix angle, the greater the loosening tendency. The greater the initial tightening, the greater the frictional force that must be overcome to initiate loosening Soft or rough clamping surfaces tend to promote slight plastic flow which decreases the initial tightening tension and thus promotes loosening Surface treatments and conditions that tend to increase the friction coefficient provide increased resistance to loosening Slotted and Castle Nuts Are used with a cotter pin or wire that fits in diametrically opposite slots and passes through a drilled hole in the bolt. this provides a positive lock but may require slight over tightening or under tightening in order to align a pair of slots with the bolt hole Terms of thread External Thread- a thread on the outside of a cylinder(Bolt, Screw) Intemal thread-a thread on the inside of a hole(Nut, threaded hole) Right Handed- Thread advances when turn Clockwise with respect to its mating part Left Handed-Thread advances when turn counter-Clockwise with respect iting pa What is Power screws Power screws( linear actuators) used to convert rotary motion of either the nut or the screw to relatively slow linear motion of the mating member along the screw axis The sliding friction between screw and nut threads has been replaced with approximate rolling contact between the balls and the grooves in the screw and nut. There is sliding friction in place of the static friction Its friction decreases drastically, with effic iencies commonly 90 percent or higher Ball-Bearing Screw to obtain a great mechanical advantage in lifting weights ( in screw-type jacks). to exert large forces,(in presses and tensile machine, home garbage compactors, and c-clamps obtain precise positioning of the axial movement( micrometer screws or the lead screw of a lathe). Properties of Ball-Bearing Screw . a brake must be used to hold a load in place. it also means that the screw is revers ible. (that is the linear motion can be converted to relatively rapid rotary motion). Smooth operation without the"slip-stick action commonly observed inIt is usually used when a very long threaded member is desired. A washer is a hardware component often used with threaded fasteners to ensure tightness of the mechanical joint. Thread Loosening and Thread Locking The greater the helix angle, the greater the loosening tendency. The greater the initial tightening, the greater the frictional force that must be overcome to initiate loosening. Soft or rough clamping surfaces tend to promote slight plastic flow which decreases the initial tightening tension and thus promotes loosening. Surface treatments and conditions that tend to increase the friction coefficient provide increased resistance to loosening. Slotted and Castle Nuts Are used with a cotter pin or wire that fits in diametrically opposite slots and passes through a drilled hole in the bolt. This provides a positive lock but may require slight over tightening or under tightening in order to align a pair of slots with the bolt hole. Terms of Thread External Thread – a thread on the outside of a cylinder (Bolt, Screw) Internal thread – a thread on the inside of a hole (Nut, threaded hole) Right Handed – Thread advances when turn Clockwise with respect to its mating part Left Handed – Thread advances when turn counter-Clockwise with respect to its mating part What is Power Screws? Power screws (linear actuators) used to convert rotary motion of either the nut or the screw to relatively slow linear motion of the mating member along the screw axis. The sliding friction between screw and nut threads has been replaced with approximate rolling contact between the balls and the grooves in the screw and nut. There is sliding friction in place of the static friction. Its friction decreases drastically, with efficiencies commonly 90 percent or higher. Ball-Bearing Screw to obtain a great mechanical advantage in lifting weights. (in screw-type jacks). •to exert large forces, (in presses and tensile machine, home garbage compactors, and C-clamps). •obtain precise positioning of the axial movement ( micrometer screws or the lead screw of a lathe). Properties of Ball-Bearing Screw •a brake must be used to hold a load in place. •it also means that the screw is reversible. (that is the linear motion can be converted to relatively rapid rotary motion). • Smooth operation without the “slip-stick” action commonly observed in