Answer / a raghunath

Runout is a composite control which results due to form,
orientation and location errors in a part. Runout is a
surface characteristic. It is always checked by rotating
the part about a datum axis and observing the full
indicator movement (FIM) of a dial indicator whcih is in
contact the the surface of the part. The tolerance zone of
runout error is a liner distance between two circles
concentric with the datum axis.

Concentricity, on the other hand, is only a locational
error of the axis of a feature with reference to the datum
axis. The tolerance zone is always cylindrical in case of
concentricity which is centered around the datum axis.
Concentricity in a plane is checked by finding the position
of the median points of the profile along different
orientations in that plane by using two dial indicators in
contact with the surface of the part and observing their
differential readings. All these readings should be less
than the specified concentricity tolerance.

A hexogonal part can be perfecly concentric with a
cylindrical part if the axis of the hexagon coincides with
the axis of the cylinder. But,for the same part runout can
not be zero as runout can be specified only for cylindrical
parts and not for any other profile.

Answer / arul - mz

Whatever Mr. Raghunath shared is 100% right.
But to be more clear to students like me....

1) If u drill a plate, if the drill bit is not placed
perpendicular to the surface, the error that can occur is
called RUNOUT. i.e., Tilt of axis of drill of hole will
lead to RUNOUT.

2) If u locate the centre of the hole wrongly over the
plate to be drilled and continue m/c., u will get
concentricity. i.e., change in location of the hole centre.

Hope I have cleared better... :-)

Answer / sadasivam

I am aggreed with Mr.Raghunath as the theoritical aspects
on runout & concentricity its deviated from the standard.
Where as Mr.Arul has totaly misunderstands the statement
given by Mr.Ragunath.

Run out is the related feature in GD&T.
It's clasified as Radial runout,Axial Runout & Total runout.

Generally runout depends form,orentation & location errors
on the part. checking the runouts for shafts with the help
of between center and dial indicator is the traditional
method what we are following at present and non magnetic
with parallel is the another one.

Radial runout is the composite tolerancing including the
effects of cylindricity & concentricity.

Total runout is the composite tolerancing including the
effects of cylindricity, concentricity,co axiality,
straightness & paralliesm along to axis.

My concern is,
between center is the right method for shafts & what about
if its in casting parts?should we go for CMM? if so what is
the method of measurement.

Concentricity
It is also related feature of GD&T on location tolerance.
Its purly matter of two circles only.its depends on form &
location errors on the part.

My Concern is,
Is it right that 2X TIR (total indicating reading)is the
concentricity error? in between center method.
is it right that 2Xaxis shifted (X or Y axis error) is the
concentricity?


Generally i have some doubts on GD&T:
1)in circle which method is well suited like LSC,MIC,MCC..?
2)Will form contributes more error in geometries?
3)Will flatness error contributs in perpendicularity
4)Will flatness error contributs in parallelism
5)in circle will form error changes the circle center axis?

Answer / sankarlal

please give one simple example in a easy method

Answer / beerappa

Hi all experienced peoples please give me example so that even beginer can understand ur explanation.

Answer / raj

Concentricity can be measured okay with CMM. If some one measuring the iuter surface of a part holding in mandrel, what they are checking is actually the run out.
In general, Runout is sufficient to take care of circularity and concentricity which can be easily measured too.

Answer / vanashri

here from all above conversation i clearly know about what is concentricity and what is runout but i am confused about checking method for both plz anyone provide details regarding this...

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