On Tue, 18 Sep 2007 00:51:45 -0500, "John D. Farr"
wrote:


"Ned Simmons" wrote in message
.. .
On Mon, 17 Sep 2007 21:34:28 -0500, "John D. Farr"
wrote:

Greetings and thanks for reading this. I have disassembled the spindle of
my
Enco 20 inch square column mill-drill to replace the pins that prevent the
collet form slipping. Now I need the procedure for preloading the
bearings.
The "manual" is worthless. Any ideas? thanks, John


The preload should be pretty low, perhaps 30 to 100 pounds of axial
force. If it's too loose you'll get chatter, too tight and the
bearings will overheat at high speeds.

First question is how is the preload determined? Spacers, shims,
adjusting nut, or something else?

--
Ned Simmons

Ned: There is an adjustment nut with a tabbed washer that is bent into the
nut to lock it down once adjusted.
thanks, John


Here's what I'd do:

-Mount an indicator to the quill with the tip on the end of the
spindle to detect axial play in the bearings. You want the indicator
fastened to the quill so you're not measuring deflection of the
machine structure.

-Snug the preload nut while checking for relative axial movement
between the spindle and quill. Use a lever between the table and
spindle nose to apply a moderate force. Rotate the spindle by hand
between rounds of checking and tightening to seat the rollers. When
the play is gone tighten the nut only to the next notch and lock it.

-Run the machine at its highest speed and watch for overheating due to
excessive preload. If you can keep your finger on the bearing or
housing it's not too hot.

-Check for play with the spindle hot and again when it cools. Repeat
from the top as required.

--
Ned Simmons