hole pattern : controlling hole-hole position 1

[Madhu454]

Hi all,

Here I have requirement , assume a rectangular block which has pattern of holes on it.

The pattern of hole is used to establish the datum. with respect to the pattern of holes the edges of the block needs to be located. now the question comes that before using the pattern of holes as datums , i need to control the orientation of hole axis to the bottom surface- this can be done by applying the perpendicularity control to holes. Along with the perpendicularity control i need to control the hole-hole distance as well.

In ISO GPS standard, if we use a perpendicularity control to the pattern of holes, the spacing tolerance between the holes is also defined. but in ASME it is not

there is a similar example fig 4-22 of 1994 std, can this be used? does this control the hole to hole distance of the pattern.

can anyone help me?

 

[pmarc]

Madhu454,
4-22 for sure controls perpendicularity of holes relative to datum A as well as hole-to-hole spacing.

May I know which ISO standard is a base for you to say that perpendicularity applied to a pattern of holes controls hole-to-hole spacing too?

 

[Madhu454]

thanks for the reply.
sure i can send you the snap shot when i go to office tomrw. i dont remmember the std number.

 

[pmarc]

Thanks Madhu454 but I have already found appropriate standard - it is ISO 2692.
I just couldn't recall and thought you could help me right a way.

 

[fsincox]

With only a perpendicularity callout?
Frank

 

[pmarc]

Yep, Frank.
Strange, isn't it?

 

[fsincox]

Thanks, pmarc
That really is, I am not crazy about that! It is almost like spite, "you guys control perpendicularity indirectly with position so we will control location indirectly with perpendicularity".
Frank

 

[Belanger]

Does ISO do this only if the pattern creates a datum? Or anytime a pattern has perpendicularity on it?

I agree with Frank. It seems to mess with the hierarchy of things. What if you really only cared about perpendicularity, and not at all about location of the holes?

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[pmarc]

J-P,
It applies every time, not only when a pattern is referenced as a datum feature (-:

 

[pmarc]

Frank,
Do not use word "location" - it is risky today. It is only spacing

 

[fsincox]

J-P,
That is exactly the kind of thing that bothers me, it is like someone doesn't think the possibilities all the way through (or from my experience, they have simplified the problem so they don't need the extra options, which we inevitably need in real world applications). This is just like the battle to have the option to orient patterns of features (as a pattern, not just features normal to a face) as a refinement of a pattern location.

pmarc,
I thought "location" was the general term we could use?

Frank

 

[fsincox]

I have been serching for a copy of this on the internet and found this:
"If you have been looking at ISO 2692 on the Maximum Material Principle, and you think you have spotted an error, you are probably right. This standard has numerous errors in the text and diagrams - use it with caution." Iain Macleod Associates
I hope they are correct!
Frank

 

[fsincox]

searching, sorry.
pmarc, I should have added this at the end of my reply to you

 

[pmarc]

Frank,
They are correct. I have an article in my hands written by one of the members of ISO GPS TC213 committee which says that Annex A contains some significant errors and should be used with caution. Unfortunately it has not been specified which specific points, figures or notes are vague. Maybe it has something to do with this perpendicularity thing.

I will try to ask him - let's hope he will clarify exactly where the problem is.

 

[pmarc]

Frank, Madhu454,

I got a response from the member of ISO TC213 committee. There is a mistake in the latest edition of ISO 2692 standard. Perpendicularity does not (cannot) control spacing between features within the pattern.

 

[fsincox]

pmarc,
Thank you, Maybe there is a god and he does not hate the ISO!!

 

[Madhu454]

Thanks pmarc,
I have already created few drawing based on this. I think I need to relook into this.

 

[fsincox]

If you reference that standard, to that date, you should be covered and just use position to do the same thing in the future.
Frank