Checking Concentricity and TIR 1

[Porknar]

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.

 

[ringster]

What is the drafting standard being applied? IS THERE ANY?
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.

 

[dingy2]

I used to see drawings like that too and found that they really meant circular runout of .001. I have also found that no datum was ever established. This was one of the reason that GD&T was initially developed - less writing with more clarity.

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.

http://www.qmsi.ca

 

[Porknar]

No real standard is being applied. We do not have a problem checking the TIR, its when they throw in the concentricity. It has been a long time since I last worked with it. Concentricity is and axial measurment, so a cylinder would have to be measured then compared to to the other cylinders to determine if they are concentric?

 

[ringster]

Without the benefit of a standard, one will have to make some logical assumptions. I would assume for this case that the concentricity requirement is making the diff diameters concentric to the axis between the ends of the shaft. (A-B) as a datum axis and the others related to it, as indicated, within .001 TIR.

 

[TheTick]

I think it is a mistake to take the concentricity in the literal GD&T sense. The drawing specifies that runout is actually measured.

 

[desertfox]

Hi Porknar

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

 

[MechNorth]

High school concentricity was the uniform offset of two nominally cylindrical surfaces.

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

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[SeasonLee]

Jim :

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

 

[dingy2]

SeasonLee:

TIR and FIM are the same.

Dave D.

http://www.qmsi.ca

 

[MechEng13]

I would second dingy2's suggestion, and add that the ideal way is to set multiple indicators on the various diameters. This is how I was taught to check concentricity. However I have also found that in most cases runout is what the designer really wants to have checked as concentricity is a difficult thing to check in the best of times. Runout is more of a functional check.



MechEng13

http://www.linkedin.com/in/alanetzkorn

 

[MechNorth]

SeasonLee,

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

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[dingy2]

Jim:

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.

http://www.qmsi.ca

 

[MechNorth]

Dave,
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

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[dingy2]

Jim:

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.

http://www.qmsi.ca

 

[MechNorth]

Dave,
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

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[SeasonLee]

Here is more information about TIR vs FIM.

http://gdtseminars.com/blog/2008/11/17/whats-the-difference-between-tir-and-fim/

SeasonLee

 

[ringster]

Porknar,

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?

 

[powerhound]

Imagining yourself as a machinist making the part is one thing. Imagining yourself as an engineer trying to communicate an idea to a machinist is something profoundly different. Don't forget that these drawings were made by engineers, not machinists. I would imagine the drawing is from the 50's and the vast majority of the drawing is covered with notes and revisions. I've seen drawings like these before. I offer this in response to your OP. I don't think there is a standard to go to that covers your exact situation so the dispute is very likely futile. Nobody is right and nobody is wrong. I think you will have to decide how to check the part and everyone get on board and do it that way.

Powerhound, GDTP T-0419
Production Manager
Inventor 2009
Mastercam X3
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[ringster]

Powerhound,

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.