Pattern of holes as Secondary datum

[Sa-Ro]

Hi

Refer attachment.

As per ASME Y14.5:2018

Design requirement:

1) Datum A will contact with mating part.

2) Two holes are used to locate and mount the part.

3) Outer surface (15) should be equally disposed from center plan of two holes (datum B).

4) Dia 8.5 holes axes coincide with center plan of two holes (datum B) and located from datum A.

If pattern of holes are datum B, how to position the pitch dimension.

In the drawing, 6 in vertical, 4 and 6 in horizontal which are locating the 2X Dia 3.3 holes. Should I make those dimension basic?

Anything to modify in drawing.

Thank you.

 

[chez311]

If pattern of holes are datum B, how to position the pitch dimension.

Pitch/pitch diameter typically has relation to thread/gear tooth dimensions. If you mean something else, as this doesn't apply to your drawing, please clarify.

In the drawing, 6 in vertical, 4 and 6 in horizontal which are locating the 2X Dia 3.3 holes. Should I make those dimension basic?

Yes they should be basic. Also as noted several times in other threads in response to drawings you have posted about, you need to either add a position tolerance, or change the perpendicularity to position - they currently have nothing controlling relative location.

The typical notation is "THRU" not "THRU ALL", the latter is a carryover from CAD functionality (ie: the solidworks option to make an extruded cut "through all"). It can also be removed as from your section view it is obvious the feature goes through the part. Speaking of which, both of your section views are notated "C", they should certainly have different designations.

 

[Sa-Ro]

Pitch means, distance between holes (6).

you need to either add a position tolerance,

Add position tolerance to where?

 

[chez311]

Ah of course. Thats not the way I typically see it used, but I know what you mean. Typically I see it in circular bolt patterns, ie: Pitch Circle Diameter not the distance between a pair of holes but okay.

Add position tolerance to where?

The 2X 3.3 holes.

 

[Sa-Ro]

TP requires location dimension from datum. But here no location from datum A.

 

[Burunduk]

Not always. Check in the standard.

 

[chez311]

TP requires location dimension from datum

No it doesn't. It requires location between features. That could be from a single hole to a datum feature, or a pair of holes to each other.

 

[greenimi]

Agree. Same like the other thread: change perpendicularity to position because you have 2x.

 

[Sa-Ro]

Ok. Ok. Now clear.

TP can be applied with single datum (perpendicularly) when minimum one location is available.

What about other GD&T notations?

 

[Burunduk]

Single datum not mandatory either. Can be without datum references at all.

 

[Sa-Ro]

In coaxial condition, right?

 

[Burunduk]

Not necessarily. Coaxial location means zero basic dimension. The basic dimension can be nonzero (some basic dimension for the spacing of parallel holes).

 

[Sa-Ro]

Datum B, right?

So that equally disposed will work for 45 and 11.

 

[Sa-Ro]

some basic dimension for the spacing of parallel holes

Any images from standard?

 

[Burunduk]

No images, but that doesn't mean it's wrong. Depends on the function of the part (I'm not talking about your case but in general).

 

[Sa-Ro]

Ok. Thank you.

 

[drawoh]

Sa-Ro,

I agree again with the notes above.

Your part is sheet metal. You want to punch the part out and bend it. The chamfers on the holes are a separate machine setup, at extra cost. As I noted in the other thread, the fabricators clean up sharp edges, unless explicitly told not to.

If this is a real part, you probably need to increase the inside bend radius.

I don't see a tolerance on the vertical face. Sheet metal shops bend to tolerances of around [±]0.4mm. Remember to take that into account in your design. Maybe you should slot those holes. This is trivial in sheet metal.

--
JHG

 

[Sa-Ro]

Ok. Thank you.