Mateus R:
I understand your post and agree with pmarc about part function driving the dimensioning and tolerancing. But please be aware of the following:
Y14.5.-2018
4.1 FUNDAMENTAL RULES
(e) The drawing should define a part without specifying
manufacturing methods. Thus, only the diameter...
I agree with everything said so far. This is a tough job to define as many have said; it is very product/process centric. Not only knowing good drafting practices - which are typically interpreted as knowing how to create "lines" in CAD but is really MUCH more - the person must have an...
Babu96:
3DDave and pmarc drilled in to the details of my post - thanks guys. J-P Belanger really defined the underlying concept - "usable space" - that one must grasp before the calculations make any sense. I use the thinking that the gauge is worst condition of the metal that a mating part...
Of note: One should understand the difference between related and unrelated actual mating envelopes (RAME and UAME) to appreciate the application of gaging concepts for datums at MMC.
Certified Sr. GD&T Professional
My two cents --- Assuming you have stated on the drawing that Y14.5 is the "dictionary" used to read the drawing: The depth symbol is all that's needed to indicate a blind-hole. The lack of a depth symbol is by default a THRU hole, so the word THRU us redundant.
Certified Sr. GD&T Professional
A first glance....make the datum feature "higher" by placing many known radial thickness "spacers" against the OD that are high enough to allow good contact of CMM probe. Not conclusive but might be the best approach for measurement.
Certified Sr. GD&T Professional
dgallup:
The OP was asking about BSC dimensions. I was trying to communicate my understanding of what determine the precision/accuracy of the true position location defined by perfect BSC dimensions, and not the precision of the measurements taken to confirm the features’ actual position error...
3DDave;
I agree with your statements. And yes, as the error approaches the limits of the tolerances measurement error get attention!
Certified Sr. GD&T Professional
Everything in the GDT world that is perfect must be simulated by processing equipment - mfg and inspection. The number of decimal places expressed in the BSC dimension is an indictor of the precision required for the part to function as intended. The accuracy/repeatability of processing...
I see no issue either. There is nothing "magic" about the .004 nominal value. The nose of the radius (or sphere) can be .011 beyond or .011 below the "square" face.
Certified Sr. GD&T Professional
A little satire here is refreshing. The "camaraderie" on this site is wonderful. I've learned a lot from everyone and it keeps my "skills" sharp. Much appreciated.
Certified Sr. GD&T Professional
chez311
I hadn't' considered this, GDT = Gosh Darn Tight (knots). Brings back memories of Boy Scout badge test it did in the 60". I was thinking it could be quantum field sting theory. But. Na.
Certified Sr. GD&T Professional
