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.

1. 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.


2. 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.


3. 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

On Aug 8, 8:07*pm, Joseph Gwinn wrote:
I recently got interested in what Franklin Hardinge, a founder of Harding *
Brothers, the predecessor of the present-day Hardinge Company, had invented.

1. *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.

It's also interesting that the thrust bearings were on the distant end
of the
headstock, not near the nosepiece. The thrust was first coupled to
the
pulleys, then through the balls to the cast iron. That has the effect
of
making any thrust-related deflection happen far from the working
end of the spindle.

In article ,
whit3rd wrote:

On Aug 8, 8:07*pm, Joseph Gwinn wrote:
I recently got interested in what Franklin Hardinge, a founder of Harding *
Brothers, the predecessor of the present-day Hardinge Company, had
invented.

1. *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.

It's also interesting that the thrust bearings were on the distant end
of the headstock, not near the nosepiece.

Yes, although I think that that was already well understood.


The thrust was first coupled to
the pulleys, then through the balls to the cast iron. That has the effect
of making any thrust-related deflection happen far from the working
end of the spindle.

Yes, but even then there was a significant (to Hardinge anyway) error due to
sidepull from the belts. I suppose the remedy of the day was to keep the
leather belts loose.

This is what Hardinge Co was remedying in 2,419,622, which was probably prompted
by the move to V-belts.

Joe Gwinn