LMB caculation 1

[SeasonLee]

Hello All

Please advise which one is correct on the LMB calculation:
Y14.5-2018---LMB = LMC - Geo Tol
Genium-------LMB = LMC + Geo Tol

Please see the attached for details.
Thanks

Season

 

[pylfrm]

SeasonLee,

Page 1 of your attached PDF appears to be correct.

Page 2 is not correct:

With only a toleranced size dimension applied to the datum feature, there is no requirement for perfect form at LMC. I'd be inclined to say this makes the LMB undefined, although perhaps some would argue that a value can be calculated. Such a calculation might not be easy for such a short feature assuming the ASME Y14.5.1M-1994 swept spheres definition is used for the size tolerance.

In the next row, the calculated LMB size is correct despite an incorrect operator in the equation. The calculation should be as follows:
1.000 - .000 = 1.000

In the last row, the LMB is drawn incorrectly. It should be entirely inside the material, not outside it. Also, the calculated LMB size is incorrect. The calculation should be as follows:
1.000 - .005 = .995


pylfrm

 

[SeasonLee]

@pylfrm
Thanks for your comments.

It should be entirely inside the material, not outside it.

This is exactly the same as what I think.

Season

 

[chez311]

Season,

I recall a similar set of examples but for MMB instead of LMB that you posted a while back that had some discrepancies. Are these also from DraftingZone? If so looks like they might need someone to double check their calculations on their materials...

 

[SeasonLee]

@chez311

You are right, but I noticed there isn't any new tips posted for a long time on their web site.

Season