KENAT
Mechanical
- Jun 12, 2006
- 18,387
I just got a really good question from an intern and it made me start to think I’m over complicating things, or maybe having a mental block, either way here goes. Attached is a sketch similar to the part he showed me but with the numbers rounded.
The part is a simple clamp plate, nominally symmetric. The only important thing functionally is the size and spacing of the 2 holes. The part gets secured in place by fasteners through the 2 holes to holes in mating part. The location of the holes relative to the edges etc is not very significant, so the pattern can move quite a bit on the part.
How would you fully dimension the part, bearing mind the need to physically identify datum’s (to avoid any ambiguity during manufacture or inspection) but not wanting to introduce excessive inspection requirements etc.
One idea I considered was adding a chamfer to one corner (shown in phantom), just to provide some kind of orientation to allow allocation of physically identifiable primary datum (and perhaps secondary & tertiary). However, it seems almost wasteful to incorporated a feature to help with dimensioning that serves no real function.
Once that’s done though, is using the 2 holes pattern as a datum (4.5.8 & figure 4-22) the logical choice? Or even though it’s not really driven by function is making edges secondary & tertiary more likely to be understood by other users while still meeting function, perhaps with composite position to allow movement of the pattern?
Working to ASME Y14.5M-1994, tried a search of this site but didn’t find satisfying answer, even though I recall some aspects of this being discussed before.
Thanks,
KENAT,
Have you reminded yourself of faq731-376 recently, or taken a look at posting policies: What is Engineering anyway: faq1088-1484
The part is a simple clamp plate, nominally symmetric. The only important thing functionally is the size and spacing of the 2 holes. The part gets secured in place by fasteners through the 2 holes to holes in mating part. The location of the holes relative to the edges etc is not very significant, so the pattern can move quite a bit on the part.
How would you fully dimension the part, bearing mind the need to physically identify datum’s (to avoid any ambiguity during manufacture or inspection) but not wanting to introduce excessive inspection requirements etc.
One idea I considered was adding a chamfer to one corner (shown in phantom), just to provide some kind of orientation to allow allocation of physically identifiable primary datum (and perhaps secondary & tertiary). However, it seems almost wasteful to incorporated a feature to help with dimensioning that serves no real function.
Once that’s done though, is using the 2 holes pattern as a datum (4.5.8 & figure 4-22) the logical choice? Or even though it’s not really driven by function is making edges secondary & tertiary more likely to be understood by other users while still meeting function, perhaps with composite position to allow movement of the pattern?
Working to ASME Y14.5M-1994, tried a search of this site but didn’t find satisfying answer, even though I recall some aspects of this being discussed before.
Thanks,
KENAT,
Have you reminded yourself of faq731-376 recently, or taken a look at posting policies: What is Engineering anyway: faq1088-1484
