What is the Measuring Methodology behind this?

[Ben1989]

Hi all,

I have some questions regarding the attached drawing (please excuse my MS Paint skills).

The smaller holes are rivet holes to hold a nut rail for the larger clearance holes. It confuses me why there is a tighter tolerance for these rivet locations rather than the larger holes.

Anyway, what is the methodology behind this? Best fit all the holes and measure the position to the best fit? Would you include these smaller holes in this or datum off their dedicated larger central holes?

Or am I way off?

Thanks in advance

Edit: it is supposed to say 'typical 6 places' not 8 places
image_18011.png

[Matthew D. Hoedeman]

The rivet holes 'do something' (get rivets) the clearance holes just need to be out of the way, that's why the tolerances

[Ben1989]

Thanks Matthew. That makes sense. What would be your measuring method for the above?

[DAN_M]

Print is under-defined. You will not be able to make a repeatable/geometrically sound alignment to measure this.

Kindly ask your imagineer to give you a datum -C- and clarify.....1) If ONE of those holes is -B-....or....2) if each hole is locally considered -B- when evaluating the t.p.s of those rivet holes. Scenario two will force you to make more alignments.

[Ben1989]

Can you have the best fit of the holes considered B? But the rivet holes aren't asked for the true position from B

[jozey]

the rivet true positions should be to B... that would make more sense to me..

[Ben1989]

the rivet true positions should be to B... that would make more sense to me..

Yes. Would you do that even though it calls for A? And would you make B all holes or just the clearance holes?

[Jakep379]

Yes. Would you do that even though it calls for A? And would you make B all holes or just the clearance holes?

I would assume so. The rivet holes have to call back to somewhere otherwise they could be anywhere? I would call the rivet holes back to there corresponding clearance hole. For the Profile i would best fit, but you still need to know if its every hole or just the clearance holes to best fit since it is attached to a clearance hole. However i would still clear this with the engineer and ask them to edit the drawing to reflect.

[Ben1989]

The tight rivet holes are obviously to control the pitch of the floating anchor nuts being fastened. Is it worthwhile doing an alignment referencing to their corresponding clearance holes, rotating to the two holes and report the true position that way?

However, thinking about it, that would allow the rivet holes to be orientated in any direction then.

[Jakep379]

The tight rivet holes are obviously to control the pitch of the floating anchor nuts being fastened. Is it worthwhile doing an alignment referencing to their corresponding clearance holes, rotating to the two holes and report the true position that way?

However, thinking about it, that would allow the rivet holes to be orientated in any direction then.

Yes. you need a "C" Or Best fit to all clearance holes that would stop rotation. Either way the print doesn't clearly depict what needs to be done

[Ben1989]

It's a very large manufacturer so there's no way I can get a drawing change in the next few months at least. It's a low complexity component and the lowest in the part classification system.

So I guess I'm wondering what I can do with the drawing that's been presented

[AndersI]

The position in Detail Z as drawn is *only* about the distance between the rivet holes - everything else is free. The rivet holes may be anywhere on the part, as they have no relation to any larger hole. The Ø sign is in error in this case.

[VinniUSMC]

The diameter symbol is not an error. The tolerance zone for each hole is still a cylinder of 0.1mm diameter centered at the basic location. The "orientation" of the cylinders also needs to be considered (ignoring the fact that the part is obviously quite thin, and like sheet metal, orientation of a cylinder through material like that is nearly irrelevant, and stupid to measure).

[Ben1989]

The position in Detail Z as drawn is *only* about the distance between the rivet holes - everything else is free. The rivet holes may be anywhere on the part, as they have no relation to any larger hole. The Ø sign is in error in this case.

So what would you do here? Datum to one of the holes and take the TP of the other one?

[AndersI]

So what would you do here? Datum to one of the holes and take the TP of the other one?

Luckily for me, I'm just software support here at Hexagon Nordic, so I don't have to follow up on all the bad prints I get to see - I'll just say "the print is in error, you need a dialog with someone responsible" and "we can guess as much as we want, but we will not know the *intent* without dialog".

Sorry, this is no help for you, unfortunately it's the truth...

As I read the print, all the large holes TP:ed together is datum B (make a group of the holes, dimension the group, DATDEF the group), the rivet holes only have a dimension on the distance between them, pairwise. I really doubt that's the intention, but there's no way to know that by only looking at the print...

[Ben1989]

I’ve got a response from one low level drawing guy just now and he says it’s to control the pitch between the rivet holes. With that said, how is it best dimensioned?

1) Measure all clearance holes and create best fit (to create Datum B) and measure TP’s
2) Translate to each pair of rivets and measure TP of the other one?
3) Measure profile to best fit