tapered roller bearing preload

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

Reply to
John D. Farr
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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?

Reply to
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

Reply to
John D. Farr

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.

Reply to
REMOVE

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.

Reply to
Ned Simmons

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.

Reply to
dee2too

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

Reply to
Nick Mueller

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 .
Reply to
Ned Simmons

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

Don't get burned!

Nick

Reply to
Nick Mueller

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