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Bushing or Bearing?
5

Bushing or Bearing?

Bushing or Bearing?

(OP)
There is some debate about the interchangablity of the terms bushing and bearing.  Many times as I peruse our company database I'll see Garlock DU bearings (and similar items) have the nomenclature of bushing.

A bushing is something that is used to support a cylindrical part.

A bearing is something that is used to reduce friction between rotating parts.

Am I off?

Ray Reynolds
"Computers in the future may weigh no more than 1.5 tons."
Popular Mechanics, forecasting the relentless march of science, 1949
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

RE: Bushing or Bearing?

There are bushings that do double duty; likewise with bearings.  Most small motors had bushings to support the rotor, but made them from copper or brass to reduce friction and galling.

In one of my older cars, the camshaft was directly supported by the bearing, so there was no separate bushing.

TTFN

RE: Bushing or Bearing?

In my view:

A bearing is any device that is used to support and reduce friction between two moving parts.

A bushing is a specific type of bearing that relies on a low coeficient of friction at the interface to perform the reduced friction portion of a bearings job.

A bearing may be rotating, linear, spherical, planer and possibly others.

RE: Bushing or Bearing?

I disagree with MintJulep's bushing definition (at least from an automotive standpoint).  A bushing is a part used to isolate two components and usually damp vibrations between them.  I also disagree with MadMango's stipulation that cylindricity is a requirement for any part associated with a bushing.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Bushing or Bearing?

I would say if it supports a rotating part, it is a bearing. If it plugs a hole, and guides a shaft then it is a bushing. That means that those motor bushings were actually motor bearings.

However, I think at least one accepted technical definition is that if there is lubricant present, oil or grease, then it is a bearing. If the device relies on the inherent low friction of the materials used to construct the shaft support, then it is a bushing.

RE: Bushing or Bearing?

sms,
How about drill bushings?  It fits the cylindrically supported description but not some of the other descriptions.

From general usage, I would consider any sleeve type bearing to be a bushing.  Whereas one would never refer to a ball bearing or roller bearing as a bushing.

Jesus is THE life,
Leonard

RE: Bushing or Bearing?

How about a transfomer bushing?

RE: Bushing or Bearing?

My company designs and manufactures plain bearing material, makes bearings and bushings and frequently our customers interchange the terms.
Consider two identical plain ordinary cylinders made of XXXX bearing material. One client will refer to them as (plain, sleeve) bearings while another describes them as bushes.
It is very confusing.
I describe it thus:
For shafting:
Regardless of lubrication, if the application to function does not require repeated relative movement of the immediate parts then it may be called a bush.
Regardless of lubrication, if the application to function does require repeated relative movement of the immediate parts then it may be called a bearing.
A bush is means to isolate and  support a shaft that does not move relative to the bush. Wear, therefore, is not a factor. It is not required to have bearing properties beyond this.
However, a bearing is a means to provide isolation and support as well as substantially reduce friction and wear between any two solid objects that repeatedly move relative to themselves. Therefore it is required to have adequate bearing properties.

RE: Bushing or Bearing?

From McGraw-Hill Dictionary of Scientific and Technical Terms, IV Edition:

Quote:

bearing "...[MECH ENG] A machine part that supports another part, which rotates, slides, or oscillates in or on it.

Quote:

bushing "...[MECH ENG] A removable piece of soft metal or graphite-filled sintered metal, usually in the form of a bearing, that lines a support for a shaft.

From these definitions, it appears to me the main functions are:

A bearing supports.
A bushing guides.

Which doesn't preclude from either one to take on additional roles or adopt different geometrical forms.

RE: Bushing or Bearing?

But, does one bearing in the hand beat two bushes in the Whitehouse?

RE: Bushing or Bearing?

2532 McGraw-Hill's definition of a bush is flawed in that it describes bushes as made of metal, ipsofacto all non-metallic 'bushes' are 'bearings'. This is just plain bearing wrong.

RE: Bushing or Bearing?

Hydrodynamic journal bearings are, sometimes, referred as bushings.

RE: Bushing or Bearing?

    I usually adopt bush bearing for components that guide and reduce friction of shaft in quarter-turn valves. Do I make a mistake?

Thanks,     'NGL

RE: Bushing or Bearing?

anegri
No, I think in one respect you have covered all the bases and on this example of frustrated logic alone you deserve a star.
The problem in the real world is just as you have succinctly described in your post. Unfortunately, for 'practical' purposes the terms are more or less interchangeable.
Sort of kind of: (did you like that? ) The distance is 25.00mm. Ah yes, but that means the distance is nearly 1 inch. I guarantee you will get a debate about it.
Personally, I think a bush is something you water or vote for. Either way, not a dynamic device nor a device that supports movement. Even though some historical references indicate otherwise, it does not justify the term bush as an accurate means to describe what a bearing is expected to do.
25362's description came really close.
He said, ...."A bearing supports"...."A bush guides"....
But, a bush also isolates.
So, perhaps, building on 25362's broad shoulders,
A bearing supports and isolates.
A bush guides and isolates.

RE: Bushing or Bearing?

rnd2,
     thank you.
     For more information, I must add that I'm Italian and we call "boccola" what we translate with "bush bearing"; in opposition to the "thrust bearing", that we call "reggispinta".
Bye,       'NGL  

RE: Bushing or Bearing?

Clearly this is another one of those terms that is "understood" differently in different sectors of the engineering world.

To make matters worse, people seem to be shortening the full term of "bushing" down to "bush".

If we are going to go that route, lets drop the "ing" from bearing as well, and just call it a "bear".

RE: Bushing or Bearing?

There are plenty of examples in the English language of the same word having more than one meaning. The recent screws and bolts thread illustrated this. "Strut" means a member loaded in compression, but a McPherson strut is different to a gas strut or a strut in a structure.

A bearing is a bearing and implies movement and low friction.

All the examples of bushes given so far are some form of a hollow cylinder. Whether they are insulating bushes, sleeve bearings or rubber vibration isolators, they are of similar geometry, and have probably been called bushes (or bushings for the pedants) because it seemed like a good description at the time.

I have no problem with a sleeve bearing being called a bush. I understand from the context what the use is.

Jeff

RE: Bushing or Bearing?

I don't ANYONE would argue that 25.00 mm is only "nearly" one inch, since the accepted conversion factor is 25.4 mm.

These discussion seem to center on the concept of "exactitude" of words, which I think is a wild-goose chase.  Even when discussing an "inch", we know that there is no exact "inch", because it can't be measured.  Everything that we do in engineering is toleranced by measurement uncertainty.

With something as crude as a single word, to which we might the notion of an uncertainty of 1/2 of the unit, e.g., the word itself, we can see that words are extremely un-exact, by their vary nature.

TTFN

RE: Bushing or Bearing?

Sorry for the horrible spelling...I'm usually not THAT bad.

TTFN

RE: Bushing or Bearing?

We'll bear with you.

RE: Bushing or Bearing?

I guess I just wasn't bushy-eyed enough yesterday

TTFN

RE: Bushing or Bearing?

Frankly, I'm bushed. To find what I seek I need new bearings but all I see is bearbush.
Sincere apologies to Anegri

RE: Bushing or Bearing?

A bushing is a type of bearing with no internal moving parts to aid in the reduction of friction, although a bushing in itself can reduce friction because it is a bearing.

RE: Bushing or Bearing?

(OP)
Aamoroso, maybe you are on to something.  If a part is singular, it has to be a bushing, but can also be a bearing... whereas a bearing may not be a bushing if it has more than one part?

Ray Reynolds
"Computers in the future may weigh no more than 1.5 tons."
Popular Mechanics, forecasting the relentless march of science, 1949
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

RE: Bushing or Bearing?

To MadMango: how would you then classify fluid bearings and magnetic bearings ?

RE: Bushing or Bearing?

Cory, I have my days when I'm disagreeable too. In fact right now I'm feeling just disagreeable enough to say  to IRstuff: Hey, this thread isn't about "aw you know what I mean".

The "McGraw-Hill Dictionary of Scientific and Technical Terms, IV Edition"  is simply wrong.  Dictionaries are supposed to based on useage, not vice-versa.  rnd2 obviously knows his stuff.

In practical use bushings most often have a cylindrical connotation.  Bearings do not have much connotation of cylindrical requirements or factors in their application.

Bearing as a noun is apparently not seen by some as being related to the verb?

BTW' Aren't bushings commonly a single piece; that is with no separate parts like many bearings have?

remember: An opinion is only as good as the one who gives it!

RE: Bushing or Bearing?

So what are what we've been calling hardened "bushings" used around the holes of a drill template supposed to be called?

RE: Bushing or Bearing?

I would call them drill guides.

RE: Bushing or Bearing?

Ah yes, BUT... the entire assembly is a Drill Guide.
I have one with interchangeable-various sized "Drill Bushings".
You might have to order a Hardened Drill Bushing, but "Hardened" is an adjective as to what specific type of "Drill Bushing" you require.

I think the whole problem is...Bushings have a "Bearing Surface". Whereas "Bearing" is a slang term shortened from: Needle Bearing, Roller Bearing, Ball Bearing, etc.

I have seen Eng. Drawings with a "Slide Bushing" nested inside of a Flanged Bushing. The inner Bushing was called a clamp-up bushing and the "Fixed Bushing" (my term) was called a Bearing.

This doesn't answer any of the questions posed, but it does show we are at the mercy of inconsistant terminology by Engineers or Drafters to lazy to research the correct terminology, but use slang from memory.

Me... I'm getting too old to work off of memory.

Rerig

RE: Bushing or Bearing?

I always thought that a "bearing surface" of a bushing was one which sees applied force, unrelated to ball bearings, etc.

RE: Bushing or Bearing?

Rerig
I have to disagree.
If the entire assembly is a template for repetitive drilling specifically located holes it is correct to call it a drill template.
I would not refer to the drill guides as bushings nor as bearings because a drill bit is not a shaft.
Hardened drill guides,
Regular drill guides,
Replaceable drill guides,
Interchabgeable drill guides. Increase the description as appropriate.
Bearing is not a slang term derived from shortening needle bearing, roller bearing etc. The preceding word or words describe more precisely the type of bearing, hence there are hydro-dynamic bearings, thrust bearings, water lubricated sleeve bearings.
 

RE: Bushing or Bearing?

Wrong wrong wrong.  Now you've touched a nerve.  People are always calling various tooling "jigs."  In specific tooling terminology (see any any tool design text), the term jig is reserved for a tool that guides the cutting tool such as a drill jig or a reamer jig.  A fixture locates and/or holds the part.  Yes a jig also locates and holds the part but also guides the cutting tool.

So then a drill jig can have many drill bushings and this is what they are called by anyone who makes them (bushings that is).  Also these hardened bushings do act as a bearing as they become subjected to side loads from the drill.  If you question this then why do you suppose they are hardened?

In engineering terminology the term bearing strength is often times used as a synonym for compressive strength which seems reasonable to me as one object "bears" against another.

In other words, a drill bushing is just another special application of a sleeve bearing although not in the typical sense that we think of as a bearing.

End of ranting now that I have vented!

Jesus is THE life,
Leonard

RE: Bushing or Bearing?

Sorry to have touched a nerve!
We make bearing and bushing material and have done for a great many years and are very familiar with both terms.
If someone wants to call something a bush and someone else wants to call exactly the same thing a bearing that's fine as long as they know exactly what they are ordering and what they are getting.
If someone asks what they should call it as they sometimes do, my answer is if there is repetitive movement either by or against the shaft it probably should be called a bearing. This implies that a bush involves minimal movement and wear.
By this criteria it is not correct to call a drill jig bushing a bearing. There is movement and wear, but no shaft.
By the same criteria it is not correct to call a drill jig bushing a bushing because there is movement and wear.
That being said a great many people will continue calling them bushings for many years to come.






RE: Bushing or Bearing?

This was my point exactly.

If you talk to a Dentist about Calculus being hard, he will disagree because he can easily remove it with a scraper.
(Unless he had a Mathematics Minor...yeah, right)

Bearing - Noun   is different from
Bearing  - Verb or Adjective.

But they are still the same????  Of Course.
Gotta' love The English Language.
(or The American English Language, or ...)
Texan spoken here.

Y'all have a good TGIF !!!!!

RE: Bushing or Bearing?

Rerig
can you give me the contact details for your dentist?
The pain inflicted by my dentist in removing calculus far exceeds the pain I suffered in learning it.
As far as bushing and bearing goes, I thought it was an object versus duty thing:
A bushing is a thing that can act as a bearing.
A bearing is the thing that acts as itself.
But what do I know; with this unbearable toothache, I may have to go bush.

RE: Bushing or Bearing?

Dogs love em.

RE: Bushing or Bearing?

What do dogs love?  Dentists, toothaches, calculus, bushings?

Horse Sense is something that horses have that keeps them from betting on people.  It also keeps them from voting for people.

Leonard

RE: Bushing or Bearing?

Now that we have that straight, what do we call the outer surface inside a turbo center section (or, inner surface bore inside  a turbo center section )  that holds, supports, guides, wears some, and maintains exact alignment of the floating bushings(?), or bearings(?),  in a
 turbocharger or on a turbo shaft ??

 

Tony Athens
http://www.sbmar.com

RE: Bushing or Bearing?

The following is a direct extract from http://www.turbomustangs.com/turbotech/main.htm
.............However, where, in my opinion, the use of the word bushing is not, or, other words are not used correctly there is placed immediately afterwards (in brackets)a more accurate alternative.
"The turbocharger shaft and turbine wheel assembly rotates at speeds up to 300,000 rpm. Turbocharger life should correspond to that of the engine, which could be 1,000,000 km for a commercial vehicle. Only sleeve bearings specially designed for turbochargers can meet these high requirements at a reasonable cost.

Radial bearing system
With a (hydro-dynamic)sleeve bearing, the shaft turns without friction (with minimal friction)on an oil film in the sleeve bearing bushing (delete words "in the sleeve bearing bushing"). For the turbocharger, the oil supply comes from the engine oil circuit. The bearing system is designed such that brass floating bushings (floating hydro-dynamic sleeve bearings), rotating at about half shaft speed, are situated between the stationary center housing and the rotating shaft. This allows these high speed bearings to be adapted such that there is no metal contact between shaft and bearings at any of the operating points. Besides the lubricating function, the oil film in the bearing clearances also has a damping function, which contributes to the stability of the shaft and turbine wheel assembly. The hydrodynamic load-carrying capacity and the bearing damping characteristics are optimized by the clearances. The lubricating oil thickness for the inner clearances is therefore selected with respect to the bearing strength, whereas the outer clearances are designed with regard to the bearing damping. The bearing clearances are only a few hundredths of a millimeter.

The one-piece bearing system is a special form of a sleeve bearing system. The shaft turns within a stationary bushing (hydro-dynamic sleeve bearing), which is oil scavenged from the outside. The outer bearing clearance can be designed specifically for the bearing damping, as no rotation takes place.

Axial-thrust bearing system
Neither the fully floating bushing (hydro-dynamic sleeve) bearings nor the single-piece fixed floating bushing (hydro-dynamic sleeve) bearing system support forces in axial direction. As the gas forces acting on the compressor and turbine wheels in axial direction are of differing strengths, the shaft and turbine wheel assembly is displaced in an axial direction. The axial bearing, a sliding surface bearing with tapered lands, absorbs these forces. Two small discs fixed on the shaft serve as contact surfaces. The axial bearing is fixed in the center housing. An oil-deflecting plate prevents the oil from entering the shaft sealing area..........."
Sources: Garrett, turbodriven.com, John Estill (www.gnttype.org) and Grapeaperacing.com

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