Cutting screws is another important task carried out in lathes. Thread cutting is the operation of producing a helical groove of specific shape ; say V or square on a cylindrical surface.
Threads can be cut on a cylindrical surface by forming or machining processes. Thread cutting by the machining process is done using a lathe. Threads of any pitch, shape and size can be cut on a lathe.
Thread cutting operation is done on a lathe using a single-point tool called thread cutting tool. The workpiece is held between cntres or in a chuck and the tool is held in tool post. For producing threads of pitch p mm, the tool must travel a distance equal to p mm as the workpiece makes one complete rotation.
The definite relative rotary and linear motion between the workpiece and tool is achieved by locking or engaging the carriage with the lead screw through a screw and nut mechanism and fixing a gear ratio between the headstock spindle and lead screw. This is done by using change gear mechanism or gear box between the spindle and lead screw.
To cut the threads, the tool is brought to the start of the workpiece and a small depth of cut is given to the tool using cross-slide. The carriage is engaged with the lead screw, the cut is made on the entire surface and at the end of the workpiece, carriage is disengaged.
The tool is pulled out of the job and brought back to the starting positions. The process is repeated until the full depth threads are obtained.
Threads can be cut on a cylindrical surface by forming or machining processes. Thread cutting by the machining process is done using a lathe. Threads of any pitch, shape and size can be cut on a lathe.
Thread cutting operation is done on a lathe using a single-point tool called thread cutting tool. The workpiece is held between cntres or in a chuck and the tool is held in tool post. For producing threads of pitch p mm, the tool must travel a distance equal to p mm as the workpiece makes one complete rotation.
The definite relative rotary and linear motion between the workpiece and tool is achieved by locking or engaging the carriage with the lead screw through a screw and nut mechanism and fixing a gear ratio between the headstock spindle and lead screw. This is done by using change gear mechanism or gear box between the spindle and lead screw.
To cut the threads, the tool is brought to the start of the workpiece and a small depth of cut is given to the tool using cross-slide. The carriage is engaged with the lead screw, the cut is made on the entire surface and at the end of the workpiece, carriage is disengaged.
The tool is pulled out of the job and brought back to the starting positions. The process is repeated until the full depth threads are obtained.
Credit :- Author-R.K.RAJPUT
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