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

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 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

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

Is there a single tapered roller bearing at each end of the shaft or
two tapered bearings together or what arrangement? Whatever you
determine the force to be, be sure to rotate the bearing several
rotations in each direction as you tighten the nut to allow the
rollers to align properly. Otherwise, they will align once they start
running and change the preload.

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

On Sep 17, 9:34 pm, "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

All posts are good advice. I would add that it is a good idea, on
tapered bearings, to go a little beyond what would seem to be good for
the preload, rotating the shaft a little as you go, to ensure the
seating of the bearings, then back off and make the final adjustment.
If you have adjusting nut, etc.

Ned Simmons wrote:

-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.

I have read (!) that the spindle has to have 50°C after 15 minutes. Don't
know how universally this can be applied.

If the bearing stays cold, there is no preload.


Nick
--
The lowcost-DRO:
http://www.yadro.de

On Thu, 20 Sep 2007 12:57:03 +0200, Nick Mueller
wrote:

Ned Simmons wrote:

-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.

I have read (!) that the spindle has to have 50°C after 15 minutes. Don't
know how universally this can be applied.

If the bearing stays cold, there is no preload.


That sounds about right. If I can keep my finger on a hunk of metal
for more than a few seconds I assume that it's not much hotter than
120F (49C). Notice how quickly I converted from F to C g.

--
Ned Simmons

Ned Simmons wrote:

If I can keep my finger on a hunk of metal
for more than a few seconds I assume that it's not much hotter than
120F (49C).

That's right. 50 .. 60°C is the I-can-keep-my-finger-on-it-for-some-seconds
temperature.

Notice how quickly I converted from F to C g.

Don't get burned! G


Nick
--
The lowcost-DRO:
http://www.yadro.de