“Checking” Bearings

There is probably not a mechanic or engineer who at one time or the other hasn’t picked up a new deep groove ball bearing, stuck two or three fingers into the inner ring and gave the outer ring a spin. When asked what they are doing, a common answer is, “Oh, just checking the bearing”.  No, all you are doing is spinning the outer ring.  The bearing has been tested after assembly at the bearing factory. There it was checked on automatic testing equipment where it is loaded and checked for precision of rotation, noise and smooth running. It is ready to use out of the box, all the user has to do is apply the proper lubrication and install it correctly.

What usually happens is that the person spinning the outer ring will complain that the bearing has too much clearance and he/she can hear a ticking noise as the outer race turns.

If a customer tilts the inner ring while holding the outer ring, a “big play” may be felt.  The reason is that a deep grove ball bearing has an axial clearance which is approximately 10 times the radial clearance.     If the customer sends the bearing in for an inspection, which takes a special machine and set up, they are always found to be O.K.

There is a reason for the ticking noise. What occurs is that with today’s packaging there is only a small amount of anti-corrosion protection injected into the bearings for shipping.  When the person holds the unloaded bearing in the horizontal position and rotates the outer ring, the unloaded balls are “falling down” within the cage pocket clearance and this gives the ticking sound. In the vertical position all balls take a small contact angle and “roll” between the inner and outer raceway, hence no more falling within the cage pocket.  If the user is not satisfied at this point, they can just add some clean lubricant  which will dampen the ball movement and the ticking will stop.

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