The lead screw of a lathe has Acme threads of 50 mm outside diameter and 8 mm pitch. The screw must exert an axial pressure of 2500 N in order to drive the tool carriage. The thrust is carried on a collar 110 mm outside diameter and 55 mm inside diameter and the lead screw rotates at 30 r.p.m. Determine (a) the power required to drive the screw; and (b) the efficiency of the lead screw. Assume a coefficient of friction of 0.15 for the screw and 0.12 for the collar.
Your manager has asked you to submit a report based on lead screws and screw jacks on plant premises. You need to include following calculations for the report.
1. The lead screw of a lathe has Acme threads of 50 mm outside diameter and 8 mm pitch. The screw must exert an axial pressure of 2500 N in order to drive the tool carriage. The thrust is carried on a collar 110 mm outside diameter and 55 mm inside diameter and the lead screw rotates at 30 r.p.m. Determine (a) the power required to drive the screw; and (b) the efficiency of the lead screw. Assume a coefficient of friction of 0.15 for the screw and 0.12 for the collar.
2. The lead screw of a lathe has Acme threads of 60 mm outside diameter and 8 mm pitch. It supplies drive to a tool carriage which needs an axial force of 2150 N. A collar bearing with inner and outer radius as 30 mm and 60 mm respectively is provided. The coefficient of friction for the screw threads is 0.12 and for the collar it is 0.10. Find the torque required to drive the screw and the efficiency of the screw.
3. A screw jack has a thread with a pitch of 5 mm and diameter 25 mm. The coefficient of friction is 0.25. Calculate the efficiency when a load is raised. Go on to calculate the effort needed to raise 6kN with a handle 500 mm long.
4. A screw jack must raise a load of 500 kg. The thread has a pitch of 10 mm and a diameter of 50mm. The coefficient of friction is 0.15.The effort is applied through a lever of radius 400mm. Calculate the efficiency and the effort required to both raised the load and lower it.
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