Repetitive feature dimension (total)

[lonsgsp]

Is the total overall reference dimension for repetitive features required to be on the drawing? Example 4 X .250 (=1.000) or 4 X .250. I recall reading somewhere that the reference dimension is either no longer used or optional. Cannot remember where I read it. Any help would be appreciated.

Thanks

 

[KENAT]

What drawing standards/revision do you work to?

...the overall dimension, if used, is identified as a reference dimension.

So based on that I'd say it's optional.

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[ewh]

While I can't claim the practice is legitimate, I have also seen it done the other way around - "(4X .25 =) 1.00". The reasoning behind it (valid or not) was to limit tolerance accumulation.

“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV

 

[KENAT]

Trouble with "(4X .25 =) 1.00" is it doesn't actually give a tolerance for the .25 values.

The alternative practice ASME Y14.5M-1994 illustrates is to make one of the .25 dimensions reference and the overall 1.00 dimension driving. Same section as before, figure 1-17.

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[ewh]

I didn't claim that the method was legitimate. ;-)

“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV

 

[drawoh]

lonsgsp,

The best argument against reference dimensions is that, on a drafting board, the reference dimensions will not be updated when changes are made. If you have advanced from drafting board, this is much less of an issue.

You need to ask yourself what the user of the drawing requires, and how much effort you should make to provide this. An additional cost of reference dimensions is that they clutter the drawing. If it useful, it is not too much work to apply it, and it does not clutter excessively, do it.

--
JHG

 

[KENAT]

... and I was just pointing out why it was ba***rd.

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