I recently got interested in what Franklin Hardinge, a founder of Harding Brothers, the predecessor of the present-day Hardinge Company, had invented. Turns out it's a lot.
- US Patent 894,634 "Lathe", to Franklin Hardinge. This is probably his original headstock design. The key is to have thrust bearings (ball bearings) independent of the axial bearings (cast iron sleeves with a precision-ground spindle within). The cast iron sleeves are tapered, and one can adjust the running clearance quite precisely by moving the sleeve, without dange of jamming the spindle.
- US Patent 2,419,622, "Lathe Spindle Drive" to Anderson. Anderson realizes that for full accuracy, one must mechanically isolate the lathe spindle from the drive pulley, so the belt doesn't pull the spindle sideways. The solution is to have the pulley running on its own bearings, and drive the spindle through a pin going from pulley to spindle, the pin axis being parallel to the spindle axis.
These two innovations appear on essentially all present-day lathes.
- US Patent 4,249,748, "One piece collet and process for making same", to Andrews. US Patent 3,669, 462", "Three and four leaf machine tool collets", to Parsons. Why Hardinge collets are so good.
Joe Gwinn