Checking Concentricity and TIR
Checking Concentricity and TIR
(OP)
A little help here. We have an old print for a shaft that reads "Diameters to be concentric within .001 TIR" Now these diameters are differnet sizes ranging from 11" to 19.5" over a shaft that is 66.5" long. Can anyone offer a defintion and an inspection method. We are having a dispute on how to go about this. Any help is greatly appreciated.





RE: Checking Concentricity and TIR
I would suppose that if you were to chuck the part up on both ends and rotate, you could verify the TIR of the various diameters.
It would be somewhat a function of just how the part was produced, IMHO.
RE: Checking Concentricity and TIR
Since the length is relatively long (almost 6 foot), I would use a V-block on both ends on a large granite table in the tool room or Quality, dial indicator on a stand and confirm the circular runout on each diameter.
Good luck!
Dave D.
www.qmsi.ca
RE: Checking Concentricity and TIR
RE: Checking Concentricity and TIR
RE: Checking Concentricity and TIR
RE: Checking Concentricity and TIR
The concentricity relates to the centreline of the shaft diameter, therefore if you have two different diameters on a stepped shaft the concentricity is controlling the centrelines of those two diameters relative to each other within the tol specified.
The only way to check as I know is as dingy2 suggested earlier.
Regards
desertfox
RE: Checking Concentricity and TIR
Prior to '66, the ANSI Y14.5 standard had concentricity and total runout as the same thing (the symbol back then was a circular line with a black dot in the middle).
Y14.5M-1994 definition of concentricity is that directly opposed points on a workpiece are centered on the datum axis within the stated tolerance. The checking of '94 concentricity requires differential opposed indicators so that you can establish the averaged center at each rotational position of each cross-section.
Without any indication of which standard to adhere to, any definition may be applicable, of course that means that any of them would be reasonable in court too if your choice was ever challenged.
As for TIR on the drawing, it does not exclusively mean "Total Indicated Runout", it has also meant "Total Indicator Reading". The preferred acronym now is "FIM" for "Full Indicator Movement" to avoid the confusion.
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Checking Concentricity and TIR
Would you please interpret in more details about the differences between TIR and FIM, why standard Y14.5M choose the term FIM instead of TIR.
SeasonLee
RE: Checking Concentricity and TIR
TIR and FIM are the same.
Dave D.
www.qmsi.ca
RE: Checking Concentricity and TIR
MechEng13
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RE: Checking Concentricity and TIR
Historically, TIR has held two meanings;
"Total Indicated Runout", and also "Total Indicator Reading".
Total Runout is a specific control, measured by an indicator along a surface rotated about its datum axis. The acronym TIR has also been used for circular runout ... is it total, or circular you want?
I can measure straightness along a cylindrical surface using an indicator. Is that measurement a runout? No, it's a total indicator reading.
That same indicator can be used to check the location, orientation or flatness of a planar surface, which is not perpendicular to an axis of revolution. Can you measure runout without a datum axis? No. So if all I have is TIR indicated on the drawing, I have to interpret which they actually want. On the other hand, if I do have a planar surface perpendicular to a datum axis, I can do a total runout on that face. So, if that face has TIR on it, which is it ... location & such of the face, or total runout of the face wrt the datum axis?
Per 6.7.1.1.1 Rotation About An Axis: "... The tolerance specified for a controlled surface is the total tolerance or full indicator movement (FIM)."
The acronym TIR is no longer used anywhere in the standard.
To say that FIM and TIR are the same thing is an oversimplification that overlooks the underlying historical connotations.
The intended meaning of the .001 TIR callout may be concentricity (high school or Y14.5 '94), Total Runout, or Circular Runout (which didn't come into the standard until 1966). Keep in mind though that Y14.5M-1994, 5.12 Concentricity, specifies that "Concentricity is that condition where the median points of all diametrically opposed elements of a figure of revolution (or correspondingly-located elements of two or more radially-disposed features) are congruent with the ais (or center point) of a datum feature." This means that two indicators are required, and that they be diametrically opposed to each other, when measuring concentricity to the '94 standard.
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Checking Concentricity and TIR
Both TIR (total indicator reading) and FIM (full indictor movement) mean the full range of the indicator from the lowest reading to the largest. Sure looks the same to me and I actually used the term TIR at GM in the late 60s (I was really young then) in the layout (CMM) room.
Dave D.
www.qmsi.ca
RE: Checking Concentricity and TIR
You seem to be ignoring the other translation of TIR; "Total Indicated Runout" ... also used for decades or longer. You are correct that "Full Indicator Movement" and "Total Indicator Reading" are the same, but they are not the same as "Total Indicated Runout"...hence the confusion, and likely the reason for the change.
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Checking Concentricity and TIR
Never heard of "total indicated runout" in my years in quality and also training in GD&T. I have had people during a couple of seminars state "total indictor runout" on a flatness requirement and I did mention that they may mean "total indictor reading" .
I have found that the automotive supply base (ones that are still surviving) in Ontario and in the Detroit area still use TIR while other areas in the USA that I might have visited use FIM.
I did notice that even the 82 standard uses FIM.
Dave D.
www.qmsi.ca
RE: Checking Concentricity and TIR
Fortunately I don't see so much of TIR or FIM on drawings anymore, though of course I do know it's out there ... lurking in the shadows!
The more exposure that I get with automotive reinforces that the Big-3 (old name, now perhaps Bankrupt-3 or Overinflated-3) have cross-pollenated their knowledge bases to the point where they do most things the same, and some of those things aren't consistent with other industries. I think this reflects the difficulty in implementing any change in a big organization
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Checking Concentricity and TIR
http://gdt
SeasonLee
RE: Checking Concentricity and TIR
For a min or two forget about USASI, ANSI, ASME. Imagine yourself a machinist with a large lathe, turning the part you have mentioned in your post. I believe the intent at that time, would be to check the TIR of the specified diameters to verify the specified dimension,while setup for the machining. Does that make sense to you? Just for a while forget the TIR/FIR/FIM jargon.
What might be the date of the drawing?
RE: Checking Concentricity and TIR
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RE: Checking Concentricity and TIR
I agree with your comments. But without the Standard being applied on the drawing and unless the drawing is revised to reflect the latest terminologies, you almost have to revert back in time. IMHO.
RE: Checking Concentricity and TIR
I know a fortune 100 company that starts with a C that has hundreds of drawings that contain the TIR note.
They follow their own standard which is an interpretation of the ASME '94 standard...er...make that try to follow it.
I saw a 3 yr old drawing that had a size tolerance on a shaft, a TIR to the other end of the shaft, a geometric position callout to the other end of the shaft, AND +/- coordinate dimensions relating features to the centers of both ends of the shaft.
(insert circus music)
Michael
GDTP-S0470
RE: Checking Concentricity and TIR
I am not so sure to measure concentricity per the 1994 standard would be the way to go, if in fact part function allows for inspection by runout. In fact with the absence of a noted standard, determining the definition of concentricty might be a struggle.
Measure in a way which makes sense relative to part function.
DesignBiz
RE: Checking Concentricity and TIR
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com