dimension scheme

[grunt58]

Is the attached drawing an acceptable way to dim the counter sunk holes? Is dimensioning their location from the center of the plate acceptable or should it be from an edge? The plate overall dims are in the top and side views.

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[looslib]

Ask yourself "How do I position and locate the part to inspect it?"
You have no dimnesnsions tying the hole patterns to the edges of the physical part.
Your dimsniosning scheme also allows the four corner patterns to not be in line with each other. You have 'clocked' the centerline to pattern dimesnion so they can be different distances from the center on the same side of the part.


"Wildfires are dangerous, hard to control, and economically catastrophic."

Ben Loosli

 

[drawoh]

grunt58,

I see no tolerances and I do not understand the function of your plate. If you apply tolerances to your drawing correctly, it is completely valid. I generally do not approve of dimensioning from centre lines, but this is valid too, if your secondary and tertiary datums are the length and width of the plate, respectively.

On a fabrication drawing, you need to balance the clear expression of your design intent, with a clear expression of what you will accept from your fabricator. Can your pitch circles be positioned sloppily with respect to each other? That sort of thing affects my tolerancing, and my dimenioning technique.

Your separate pitch circles would have been recalculated into rectangular coordinates by a machinist, thirty years ago. Today, they just punch it into their CNC. How is your inspector going to cope with this.

JHG

 

[KENAT]

As others, the sketch is so incomplete it's difficult to say for sure.

Are you using GD&T? If so and the the secondary & tertiary datums are length & width of the part then it may be legit like drawoh says.

Without it then at best it's problematic, as shown it's jut plain wrong/incomplete since you haven't located the 'centerline'.

Use of 'TYP' is not explicitly supported by any drawing standard I'm familiar with. Per the last few additions of ASME Y14.5 I believe you should give the explicit number 'X'. e.g. 4X Ø 2.756.

Dual dimensioning is also problematic.

While 'THRU' is in the spec, 'THRU ALL' isn't, so there's no explicit definition of the difference in meaning.

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