I understand the definition of the resultant condition (RC) for MMC and LMC, but what I fail to understand is how they are applied. A search of the 2018 revision found no hits for resultant condition outside of the table of contents and the figures in section 5.
Using an external feature at MMC as an example (Figure 5-17) and considering a positional tolerance:
- The VC defines the outer boundary that the feature cannot violate. From a gaging standpoint this makes sense. Make a hole this diameter, with perfect form at the true position and see if the feature fits.
- The RC would appear to be an inner boundary in the sense that the external feature (boss) must completely envelop this boundary. The RC surface is generated assuming perfect form, and per the standard, perfect form is only required at MMC. So if you have a bowed boss at LMC and the full offset allowed by the positional tolerance, it would not completely envelop the RC. Since the RC isn't referenced anywhere else in 14.5, I don't really understand how (if at all) it is used? Does it show up in the gaging standard? Is this a holdover from previous revisions and they just didn't want to redo the figures?
Here is my understanding of how such an external feature would be checked for size and position:
- a functional hole gage at VC would be used to check the positional tolerance (surface method)
- local diametric (for cylindrical boss) measurements would check that the local sizes are all greater than the LMC
then...
Practically speaking, how does one check that the positional tolerance of the UAME is within spec (i.e. within positional tolerance + bonus) of true position? Does this just not matter when the positional tolerance is specified at MMC, since the goal is fit and if the local sizes are all good and the VC isn't violated, then it'll fit?
I assumed the axis method would be employed for this, but this would appear to be somewhat more difficult to check in practice (scanned and digitally created UAME?). The advantage of the RC would be the simplicity of checking it. Just project the boundary (e.g. laser circle) and make sure every part of the boundary hits some part of the feature. My problem is that this does not seem to be addressed anywhere in 14.5.
W.R.T. RFS features, the inner and outer boundaries are causing me similar issues. They aren't referenced anywhere outside the table of contents or the definition figures in section 5. The text of 14.5 indicates that the surface method is not applicable RFS, so these seem moot. You would need to establish the axis of the UAME and then use the axis method to check position. The same local diametric measurements would be used to check adherence to the the size tolerance.
Using an external feature at MMC as an example (Figure 5-17) and considering a positional tolerance:
- The VC defines the outer boundary that the feature cannot violate. From a gaging standpoint this makes sense. Make a hole this diameter, with perfect form at the true position and see if the feature fits.
- The RC would appear to be an inner boundary in the sense that the external feature (boss) must completely envelop this boundary. The RC surface is generated assuming perfect form, and per the standard, perfect form is only required at MMC. So if you have a bowed boss at LMC and the full offset allowed by the positional tolerance, it would not completely envelop the RC. Since the RC isn't referenced anywhere else in 14.5, I don't really understand how (if at all) it is used? Does it show up in the gaging standard? Is this a holdover from previous revisions and they just didn't want to redo the figures?
Here is my understanding of how such an external feature would be checked for size and position:
- a functional hole gage at VC would be used to check the positional tolerance (surface method)
- local diametric (for cylindrical boss) measurements would check that the local sizes are all greater than the LMC
then...
Practically speaking, how does one check that the positional tolerance of the UAME is within spec (i.e. within positional tolerance + bonus) of true position? Does this just not matter when the positional tolerance is specified at MMC, since the goal is fit and if the local sizes are all good and the VC isn't violated, then it'll fit?
I assumed the axis method would be employed for this, but this would appear to be somewhat more difficult to check in practice (scanned and digitally created UAME?). The advantage of the RC would be the simplicity of checking it. Just project the boundary (e.g. laser circle) and make sure every part of the boundary hits some part of the feature. My problem is that this does not seem to be addressed anywhere in 14.5.
W.R.T. RFS features, the inner and outer boundaries are causing me similar issues. They aren't referenced anywhere outside the table of contents or the definition figures in section 5. The text of 14.5 indicates that the surface method is not applicable RFS, so these seem moot. You would need to establish the axis of the UAME and then use the axis method to check position. The same local diametric measurements would be used to check adherence to the the size tolerance.
