Hey? y？ U9？ 09 Na is? 〇？ M In the15th century, due to the need of making clocks and weapons,
Clockmakers have thread lathes and gear processing machines.
And a hydraulically driven cylinder drilling machine. About 1500, Italian Leonardo da Vinci drew sketches of lathes, boring machines, thread processing machines and internal grinder.
Among them, there are new mechanisms such as crank, flywheel, gyro and bearing. There is also the structure of a grinder in Heavenly Creations published by China in the Ming Dynasty. The iron plate is rotated by pedaling, and the jade is cut by adding sand and water.