One of the big advantages of having a lathe is being able to machine threads. Many threads can be cut using taps and dies, but having a tap and die set that will enable you to cut all the non-standard thread sizes would be very expensive.
The thread-cutting attachment uses a set of metal gears to coordinate the movement of the spindle and leadscrew. Hand-cranking the drive gives you the ultimate in control where the small size and short lengths normally encountered on a lathe this size make a motor-driven engagement unnecessary. It also allows the control to cut threads right up to a shoulder.
Sherline offers a unique and versatile thread-cutting attachment for its lathe. This low cost attachment enables you to machine 36 different unified thread pitches (Pitch range from 80 to 5 threads per inch) and 28 different metric thread pitches (Pitch range from .25 to 2.0mm). What’s more, it allows you to cut them as either left-hand or right-hand threads. The lathe tool can be ground to cut any of the various thread forms, and any of these various pitches or thread forms can be cut on any pitch diameter you desire. This versatility enables you to machine any standard or nonstandard thread you need as long as it is within the size limitations of the lathe.The attachment consists of 15 accurately hobbed metal gears, mounting brackets, engagement mechanism and a 4" (102mm) handwheel to drive the spindle.
Threads are generated on the Sherline lathe by gearing the spindle to the leadscrew. As the spindle is rotated with the handwheel, the tool will advance an amount determined by the ratio of the gears. When the tool has completed its movement, you simply stop cranking, back up the tool and turn the spindle in the opposite direction until the tool is past its starting point. Then reset the tool depth and you’re ready for the next pass. It’s as simple as tapping! By using a 127-tooth gear (supplied), true metric threads can be cut on an inch (model 4000, 4500, or 4400) or true inch threads on a metric (model 4100, 4530, or 4410) lathe. A complete gear ratio chart and detailed instructions are included.
Download PDF 3100 Instructions