https://youtu.be/gMt-9mKQSjs
https://youtu.be/uuR2Z60KYos
■ screw thread
A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force.
A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread.
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