Bearing preload

[WCraig]

So, I'm trying to resurrect an very old Dumore tool post grinder. Some previous owner has, I think, remade the spindle (aka quill) and thrown away some parts! I don't know for sure as I can't find a parts list that corresponds to the model I have. Mine was apparently designed for a "total loss oil" lubrication; not sealed bearings. There is a Gits oiler cap on the housing and an old Care & Operation (C&O) manual says to add a teaspoon (!) of oil each 8 hours of operation. I believe the idea is to continuously flush out any grinding debris from the bearings.

The spindle that was in the grinder when I got it is bent. I'm sure it is user-made rather than original. Below is a picture of the parts. As it stands, the spindle goes in the bearing and then fits into the housing tube. A cap threads on and bears against the outer bearing race only.



The C&O manual says that the grinder is "equipped with a specially designed internal preload arrangement" that "maintains the correct preload on the bearings, even though the spindle expands and contracts due to heat changes." There are no details, however, on that preload arrangement.

I tried contacting Dumore for any information they could provide but haven't received any response in the last two weeks.

To sum up, I think I should add preload to the bearings but I don't know how this was done originally.

AIUI, the preload is pushing the inner race one way and the outer race the opposite direction, right? So the balls in the bearing riding against sides of the race rather than in the valley. [1]

I'm guessing that I need some kind of flat spring washer. Maybe:

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

or

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

What size do I want? Does the spring press against the inner race, the outer race or both?

Thanks in advance,

Craig

[1] https://www.nationalprecision.com/library/articles/bearing-preload.php

 

[WCraig]

The Care and Operation manual I mentioned is from the Vintage Machinery site:

Wisconsin Electric Co./Dumore Co. - Publication Reprints - Care and Operation of Dumore Toolpost Grinder | VintageMachinery.org

vintagemachinery.org

Craig

 

[Ulma Doctor]

typically, ball bearings (radial bearings) are not pre-loaded.
pre-loading a radial bearing will drastically reduce the service life of the bearing.

by contrast, tapered roller bearings and angular contact bearings are made for taking thrust loads and require pre-loading.
they are used in sets, the bearings are usually used in opposition proximity.
pre-loading rates vary with the bearing size and type, some taking mere ounces of preload, some taking hundreds of pounds of preload (thousands in very large assemblies)

on a small shaft like that, to pre-loaded bearings i would make the pre-load be done by feel.
i would tighten the ring until the shaft is nearly prevented from rotation, then backed of to loose, then back to Zero Clearance.
the shaft should move effortlessly to very slightly dragged, in feel.
any hesitation or bind may indicate, shaft off center, overtightening, or lack of lubrication.

 

[WCraig]

Aha. I was going to ask about the type of spring washer to use when I finally noticed that the McMaster-Carr listing says "for R4A..." which is what I'm using.



Now I just have to find a source for these in Canada.

Craig

 

[machPete99]

Here is one Dumore spindle setup, not sure of the exact model but is similar to my 44.
Note that the shaft diameter increases towards the bearings, which causes the oil to flow towards the bearings.
On mine there is also some cotton wicking material used to direct the oil.
Preload is done by a combination of the wavy washer and threaded end pieces.

 

[John O]

Try Canada bearing or Ontario Belting. If not, I think McMaster will ship to Canadian companies.

 

[WCraig]

Here is one Dumore spindle setup, not sure of the exact model but is similar to my 44.
Note that the shaft diameter increases towards the bearings, which causes the oil to flow towards the bearings.
On mine there is also some cotton wicking material used to direct the oil.
Preload is done by a combination of the wavy washer and threaded end pieces.

Thanks very much. The C&O manual mentions a "Dumore patented lubricating system" which must relate to the tapered portions of the shaft. Squinting now at the picture in the C&O manual, I can sort of make out that it shows tapered portions as well. Your picture is vastly better.

Craig

 

[WCraig]

Try Canada bearing or Ontario Belting. If not, I think McMaster will ship to Canadian companies.

I don't have a company that I can run the purchase through so McMaster is a problem. Plus shipping from the USA can be very slow and/or crazy expensive.

We're painting a couple of rooms this weekend (ugh) so maybe after that I can spend some time on my project.

Craig

 

[Ulma Doctor]

Aha. I was going to ask about the type of spring washer to use when I finally noticed that the McMaster-Carr listing says "for R4A..." which is what I'm using.

Now I just have to find a source for these in Canada.

Craig

point of information, this spring doesn't pre-load the bearing
it merely holds the bearing in place, restricting lateral movement

 

[WCraig]

point of information, this spring doesn't pre-load the bearing
it merely holds the bearing in place, restricting lateral movement

I don't follow. What does provide the pre-load then?

I do know that the other issue is differential expansion of the spindle versus the casting that the bearings mount in. As the parts warm in use, the spindle length will increase at a different rate than the housing. I thought the spring was to provide pre-load while accommodating the change in length. No?

Craig