Bearing Preload w/Lovejoy Connector

[rcazwillis]

Is is suitable to use a lovejoy connector to clamp the center piece of two bearings together to get my preload? I don't know if the single set screw in the connector will hold the pressure. My delima is the fact that I don't have any threads on the end of the ball screw. If I thread it, then I need to turn down the end for a connector to fit.

How should I proceed?

[NC Cams]

Depends on how much preload force you're trying to maintain and if you can maintain tightness of the setscrew once you do obtain the necessary preload.

If you can't assure that the tighness of the setscrew can be maintained, you already have answered your own question.

You don't have to turn the end of the shaft down for a nut. You can drill a hole in the center of the shaft and then tap it. You can then apply claming force to the end of the coupling via careful placement of a bolt into the end of the shaft.

Oh, and proceed carefully if you preloading a deep groove, non angular contact built in preloaded ball bearing....

[rcazwillis]

Good idea on the drill & tap. That will work.

The bearings I plan to use I got off Ebay. Numbers on them are 6202-2RS. I have no idea of the brand. It was listed as an angular contact bearing.

[jeffs555]

I think, a 6202 would be a deep groove bearing. The number for a metric angular contact bearing should start with a 7. This page has a good explanation of the numbering system for bearings. http://www.gizmology.net/bearings.htm

[NC Cams]

Jeffs55 if correct, your part number indicates that you have a 6202 deep groove ball bearing with 2 seals. It, per se, is NOT an angular contact bearing.

It would have to be a have a 7202 prefex to be a true, angular contact ball bearing.

Perhaps, and I do mean PERHAPS, if the bearing were custom reworked into a preloaded configuration by special grinding the face of an inner or outer ring, you would have a preloaded deep groove bearing.

This type of modification tended to be rare as they are/were only custom made for special situations when I was in the industry.

If this were the case, a reputable rework facility would etch a chevron ( >) on the bearing OD to show mounting orientation. I'd be leary of the part being properly reworked/preloaded if does not have the chevron.

EDIT: The LAST paragraph of my initial post is PARTICULARLY and signifigantly important in light of the part number and bearing design that you are trying to preload.

[RICHARD ZASTROW]

rcazwillis just a thought. 5302 or 5202 double row angular contact bearings are self preloaded and can be ordered with seals and or shields. the combined width of a pair of single groove angular contact or deep groove bearings is also wider than the width of one double groove bearing of the same id, od and ball compliment. save a bit of length.
RZ

[rcazwillis]

I seriously doubt that anything special has been done to these bearings. So, should I preload a bit or just run them as is.

[NC Cams]

To correct a popular misconception: Double row angular contact bearings (IE 5302 or 5202's) ARE NOT, I repeat and emphasize NOT internally preloaded. Manufacuring tolerances preclude the possibility of making them that way.

They do have axial and radial clearance potential (Reference NSK Technical ReportNo. E728, Topin 4.9, Page 102 dated 1992) and one affects the other.

By doing/applying an axial load and measuring the inner ring deflection, it is possible to confirm this. However, be prepared to measure in microns (0.001mm) as that is the units of measure used to confirm/quantify load versus deflection curves.

A double row bearing is capable of absorbinhg axial thrust MUCH higher than a 6202 or 6302 du to the angular contact potential of the raceways but they are TECHNICALLY NOT preloaded - not like the true preload, negative clearance as would be generated in a preloaded 7202CTYDUL, DUM or DUH bearing.

Re: use of the 6202's as is. What are you trying to do????

You can preload them with a wave washer to reduce axial slop. You can get these from McMaster Carr or perhaps Grainger. This will reduce axial slop and enhance running accuracy. This is a common practice in electric motors which is what the wave washer thingie is used for. However, as soon as you overcome the preload, you regain any axial slop you removed and instability will recur.

If you are looking for TRUE axial stiffness enhancement (like that needed for a milling spindle), you're pretty much going to have to use something like a 7202 with an appropriate built it preload or specially preload the 6202's you have..

Before the "but this is for a whatsit and I don't need an abec 7 bearing" replies start, check out the preload tables of a 7202DU( ) versus the preload potential for a wave washer copressed to the listed height.

Pick and choose as you require/truly need and make your choices based upon the numbers, not rumor, inuendo and/or sage wisdom..... If the wave washer preload suffices, fine, use it. If it won't, then you may need to spend the money for the 7200's.

The information presented in your original post is insufficient to make a 100% accurate recomendation one way or the other.....

[RICHARD ZASTROW]

NC CAMS I stand corrected. I thought I read somewhere there was a light preload that could be increased by interference fit. After checking my SKF specs. a C2 spec would be somewhere whithin 1-12 microns clearance for 5202A2RS ABEC-1
RZ

[rcazwillis]

I plan to use the bearing(s) on the Y axis of my HF 12 speed mill. I have a ball screw for the axis and the 450 in-oz motors. How do I maximize the accuracy of these bearings in this application.

Thanks for all the data so far. It is greatly appreciated.
Rick

[NC Cams]

Replace them with 7202A5TYDUHP4's

Next option is to buy some relatively inexpensive 7202BYG"s and have them preloaded with about 390N by KAF in DF config by KAF Manufacturing is in Stamford, CT

Cheapest and last option is to ask KAF if they can preload the 6202's with 50-70 lbs preload in DF configuration. You WILL have to clamp the inner and outer rings TIGHT when this is done - forget the lovejoy idea - make the space and do it right.

NOTE: the preloaded 6202's won't/can't run as smoothly or as freely as the 7202's mentioned above - long story why.

These are THE options to "maximize" your accuracy. You can kluge together any number of other fixes but these are your best alternatives.

[RICHARD ZASTROW]

NC CAMS You can get double row 60 degree angular contact with split inner races preloaded. They have thick (.984") large od (2.362") with mounting holes thru the outer race. These are designed for ball screw support. Unfortunately, they are quite expensive. INA gave me a price of $848 ea.! This is a 15mm (.591") bore p5.