Question about ball bearings

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Forum topic by D_Allen posted 05-28-2011 03:25 AM 1008 views 0 times favorited 7 replies Add to Favorites Watch
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495 posts in 2202 days

05-28-2011 03:25 AM

Does anyone know what the term or reference is that refers to this condition.
If a ball bearing has play between the coplaner inner and outer races, what is that called?
Is that the lash?
Put another way, suppose the bearing is laying horizontally on a flat surface. If the inner race can move upward while the outer race stays flat, that is called what. I know it is called bad or busted or whatever else.
I am trying to determine if this is a specification that can be compared.

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7 replies so far

View lew's profile


11263 posts in 3173 days

#1 posted 05-28-2011 03:29 AM

I always thought lash referred to the “play” in gears when reversing their direction.

-- Lew- Time traveler. Purveyor of the Universe's finest custom rolling pins.

View ClayandNancy's profile


511 posts in 2433 days

#2 posted 05-28-2011 03:37 AM

in repairing differentials, backlash was the clearance between gears. Preload was the tightness of tapered roller bearings, basically no play. I don’t know of the term used for roller bearings with that play other then BAD.

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2619 posts in 2526 days

#3 posted 05-28-2011 04:14 AM

I call it end play. Here’s a link to a site that discusses it:

Play and lash are two different critters.

-- Random Orbital Nailer

View buckeyedudes's profile


150 posts in 2545 days

#4 posted 05-28-2011 04:17 AM

Technically it is called ‘Radial Internal Clearance’ or RIC.

This ‘play’ is what is engineered by bearing manufacturers so when you press fit the bearing on a shaft, the bearing will have the correct amount of looseness/tightness yet not burn up.

Therefore, you MUST follow the bearing manufacturers specified fit on the shaft.

-- Before you louse it up, THIMK!

View D_Allen's profile


495 posts in 2202 days

#5 posted 05-28-2011 04:31 AM

OK, thanks all.
That article that AtomJack referenced is good info and apparently what I want to refer to is the axial play.
The reason for this post and question is in reference to the ball bearings on the corner adjusting posts of my R4330 planer. All of the force applied to these bearings is in the direction of the post. When the cutter and rollers are in action, that puts axial force on the post bearings. I have found some vertical play in the posts so I may take it apart and see if it is the bearings or spacers.
Thanks again all.

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philip marcou

262 posts in 2014 days

#6 posted 05-28-2011 05:40 AM

It is indeed end play, axial play or end float .But D Allen should not get too neurotic about the bearings he mentions as these things can be misleading when one is trying to determine what an acceptable amount of play is , without some experience and tools. My procedure is if I have stripped the machine for a rebuild or repair I just replace any of the common bearings as they are cheap. I once had access to a friends ultra sound cleaning machine and would clean replaced bearings this way provided they were not the sealed type and keep them as spares.
I have a book called the “SKF General Catalogue” which has proved mighty useful and I recommend any woodworker with machines to get one: bearing agents and dealers used to hand them out but I don’t know if that is still true.

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495 posts in 2202 days

#7 posted 05-29-2011 03:22 AM

Well, I don’t think I’m neurotic, but I am inquisitive!

There is about a .002” vertical play on the corner adjusting post of my planer. It is a kind of movement that indicates it is not squeezing or bending something. Rather it is a definite movement with a stop. I get this using a 2 foot piece of wood wedged under the upper frame( with very little force by the way) and it is measured between the screw post and the base. I checked the base and it is not flexing. The image below shows the stack of parts(NOTE: the brearing and retainer are actually bigger in diameter than it shows here). The gears are nylon and everything from the bearing retainer to the bottom screw is connected to the shaft. I put a shim behind the bearing retainer to be sure the bearing was not moving within the socket. The only thing left is the axial tolerance. Could these bearings be so cheap as to have a .002” movement? It seems unlikely. I have no way to check them unless I remove one and if I am going to do that I may as well replace them all

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