INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Jobs

Bearing housing tolerance limit

Bearing housing tolerance limit

(OP)
Hi,

I would like to confirm the tolerance limits for a ford fiesta bearing. I am new to this so please bear with me. The bearing has an outer diameter of 72 mm, inner diameter of 37 mm and a width of 37 mm. It is a ball bearing. From what I found (here http://www.nskamericas.com/cps/rde/xbcr/na_en/CNSK...), the housing tolerance is of category N7 and from another source (http://www.ntn.co.jp/english/products/catalog/pdf/...) the housing tolerance limits are: +0.039/-0.004 mm.

I would really appreciate it if someone could confirm this for me.

Thanks

RE: Bearing housing tolerance limit

The tolerance depends on whether the outer or inner ring is stationary, and whether the direction of load is constant (like gravity).n

pages 3 thru 7 at the link you provided

RE: Bearing housing tolerance limit

(OP)
Thank you for your reply. How can I determine whether the inner or outer ring is stationary? Am I the one who fixed which is stationary or do bearings already have preset stationary inner and outer rings? Also could you help clarify the stationary and rotating load cases for me with an example?

Thanks

RE: Bearing housing tolerance limit

The bearing mfr does not know how you are going to install their bearing.

A regular electric motor has a rotating shaft and inner race/ring, and stationary outer race/ring.

A 1959 Chevy Impala front wheel has a stationary inner ring and a rotating outer ring.

In each case the load (gravity) is essentially one directional for the stationary ring, so it can be designed with a slip fit in/on it's "seat" (the shaft/housing.)
However in each case the load varies direction relative to the rotating ring, so they must be an interference fit with their seat, to prevent creep and attendant wear and destruction.

If there are multiple loads or with a vertical shaft then it is possible to end up with loads varying direction for both rings, which requires clever compromises to permit adjustment or assembly.

RE: Bearing housing tolerance limit

In the specific case of wheel bearings it is sometimes necessary to go away from the standard fits, due to brake temperatures. I always got Timken to double check my design when we used taper rollers, as we tended to get some odd setups.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Bearing housing tolerance limit

(OP)
Thank you Tmoose and Greg for your replies.

Please let me know if I am wrong here: bearings in steering knuckles usually have stationary outer rings and rotating inner rings which means they have to be fitted with a given interferance on knuckle center hole. In this case, the tolerance will be of category N7 (interferance of 0.039 mm and clearance of 0.004 mm) as I mentioned in my first post.

RE: Bearing housing tolerance limit

" bearings in steering knuckles usually have stationary outer rings and rotating inner rings " the only way of telling is to look at the design of your car, whichever bit goes round with th wheel is the roatating one. We use both possibilities on the same platform. A powered axle is likely to be stationary outer for obvious reasons, but for a non driven wheel there are good reasons to use a carrot and a rotating outer.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Bearing housing tolerance limit

(OP)
I am dealing with a front knuckle for a front driven vehicle. In this case, I think I am safe assuming that the outer ring is stationary.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close