ASME Y14.5-2009 - Total runout example
ASME Y14.5-2009 - Total runout example
(OP)
Looking for one information related to total runout, I found in Y14.5-2009 standard, section 9, figure 9-7 a callout that looks really weird to me. Datum feature D is controlled with total runout 0.05 relative to C primary and D secondary. Is it only a typing mistake or something more stands behind this specification?





RE: ASME Y14.5-2009 - Total runout example
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: ASME Y14.5-2009 - Total runout example
Yes it looks weird but it is valid. The 94 standard has an identical example in fig. 6-52 with the exception that the feature control frame reflected circular runout rather than total runout.
The feature that will become datum D has very little length and I really don't know how one could confirm the form. There just isn't enough length by itself for roundness or cylindricity so we do need datum A for set up. We then have a choice of circular or total runout.
I agree with Jim that chicken and egg thoughts do occur in this example. Should one have datum D before referencing it? This is a bit of an exception.
Dave D.
www.qmsi.ca
RE: ASME Y14.5-2009 - Total runout example
RE: ASME Y14.5-2009 - Total runout example
I find that many inspectors aren't trained as such; they're typically veteran machinists who have been booted up the line. I haven't heard of a professional metrology training program or certification yet ... shame, really, because it would be a major step for North American industry.
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: ASME Y14.5-2009 - Total runout example
Chuck at the end of diameter datum D and then using a dial indicator on the face which is datum A, true up the face. One would tap the face with a hammer until one had as close to zero TIR on the indicator as practical understanding that the face may not be perfectly flat.
Now datum D at our contact point is perpendicular to datum A.
One would then take the dial indicator (on a stand of course) to the highest point on the diameter (centre) of datum D and rotate recording the highest and lowest reading. Move the dial indicator along the length and, again, move it to the highest reading (centre) and rotate the part recording the highest and lowest reading. DO NOT RE-ZERO the indicator. One can take a third reading if desired.
The total runout is the range from the smallest reading taken from all readings to the largest reading. This will include circularity, taper, straightness and maybe a bit and angularity if the OD was not truly perpendicular to datum A.
It is not that hard to do.
Dave D.
www.qmsi.ca
RE: ASME Y14.5-2009 - Total runout example
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: ASME Y14.5-2009 - Total runout example
RE: ASME Y14.5-2009 - Total runout example
If we decode the Total Runout FCF for feature D in Figure 9-7, here's what we get. The entire surface of D must lie within a tubular tolerance zone of wall thickness 0.05. The tolerance zone is perpendicular to Datum C. The zone is also coaxial to Datum D, which is the axis of the related actual mating envelope of feature D.
To me, the requirement for the zone to be coaxial to D is artificial. It's only there because of the limitations of the Y14.5 tool set. The real functional requirements are that the feature be nice and cylindrical and perpendicular, so that it acts as a good stable secondary datum feature. So the Total Runout zone just needs to be perpendicular to Datum C, it doesn't need to be "self-centered". It needs to have Total Runout within .005 to some axis, but we can pick the axis. But there isn't a way of saying that in Y14.5 - a Total Runout FCF must reference a well-defined datum axis. So they came up with the idea of making the feature a datum feature for its own runout control. But this adds in an extra constraint that is highly impractical, not necessary, and (I would say) often ignored.
Figures 9-7 and 9-6 are nothing new, they are literally as old as I am. They are based on figures that were in USASI Y14.5-1966, and are essentially unchanged. So the concept of self-referencing runout has been around a long time, and has survived mainly because it has been around a long time. But it doesn't stand up to close scrutiny, and will go away if and when rigor is added to Section 9.
Luckily we don't have the same problem with other characteristics. Take the common example of a cylindrical hole that is nominally perpendicular to a primary planar face A. The hole is going to function as a secondary datum feature, so we just need to control its orientation to A and label it as B. The control would typically be Perpendicularity to A. Or perhaps Position to A, which is equivalent in this case. But nobody would specify Position to A and B! It's not necessary to reference the secondary datum feature to itself! Yet that is exactly what we have in Figure 6-7.
Evan Janeshewski
Axymetrix Quality Engineering Inc.
www.axymetrix.ca
RE: ASME Y14.5-2009 - Total runout example
The issue with positon tolerance on a cylindrical hole that is nominally perpendicular to a primary planar face A was exactly the next thing I was going to ask.
RE: ASME Y14.5-2009 - Total runout example
Other than that, I agree with Evan's post!
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: ASME Y14.5-2009 - Total runout example
I would say that using a Position tolerance for an orientation-only relationship is "not necessary" or "not preferred". "Not correct" is a bit too strong for me though. But I agree that using an orientation tolerance is more clear.
I suppose that this is similar to using a Surface Profile tolerance on a single planar surface, with no datum features. Would the existence of the Flatness tool make that not correct as well?
Evan Janeshewski
Axymetrix Quality Engineering Inc.
www.axymetrix.ca
RE: ASME Y14.5-2009 - Total runout example
But with position, the very definition is to control "the location of one or more features of size relative to one another or to one or more datums." (Para. 7.2 of the new standard; similar concept in para. 5.2 of 1994).
So to use position to control only orientation is not meeting the fundamental purpose of position, which is location. Sorry if I got us off topic; I didn't mean to stir the pot :)
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: ASME Y14.5-2009 - Total runout example
You are correct about positional tolerances controlling location, orientation of non-round features of size and perpendicularity. If one did not place a positional tolerance on a feature of size, how does one arrive at a tolerance of location?? Could it possibly be a +/- tolerance?
Dave D.
www.qmsi.ca
RE: ASME Y14.5-2009 - Total runout example
To leave off this note would yield an ambiguous tolerance for that feature's location, since we can't make the implied datum features (the two edges) perfect every time. Even if the location is not that important, it must have a location tolerance -- perhaps a very generous number -- and the origins for those locating dimensions must be clear.
Hey, are you trying to stir the pot now?
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: ASME Y14.5-2009 - Total runout example
Evan Janeshewski
Axymetrix Quality Engineering Inc.
www.axymetrix.ca
RE: ASME Y14.5-2009 - Total runout example
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: ASME Y14.5-2009 - Total runout example
Robert Bohot
GDTP-S
RE: ASME Y14.5-2009 - Total runout example
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: ASME Y14.5-2009 - Total runout example
As I understand you are on the committee, did you express your concerns there? Are you not in favor of compound datum applications, in general (other than the traditional "A-B" centerline? I think is ironic that people will say any given example from the standard should not be "done like this" when it is just an example in the standard, probably given just to show that concept in particular, I doubt those parts even really exist, they are just simplified concepts, are they not? Is that a particular application the committee knows? My guess is they are laying the groundwork for the complex datum frameworks that do actually occur in real life.
Frank
RE: ASME Y14.5-2009 - Total runout example
Frank
RE: ASME Y14.5-2009 - Total runout example
Frank