Engineer wants me to show dual tolerance on drawing. Below is the tolerance shown on existing drawing. I don't know +- .03 and +-.010 are in inches or in mm?
How do I include dual tolerance on drawing? Thank you
Yes you need to put the correct values there. I was only suggesting to add units so that one can see the difference.
You can also do something like this depending on which units are the primary ones (they stay outside of brackets ).
Just add the tolerance with the units. For example ± .03" ± .03mm
You don't convert that .03 and .010?
I see. Thank you
Please be careful to add this to the title block as it might mislead the inspector to perform double jobs in both mm and inches - see my response below
For standard practice, you shouldn't have dual decimal places in the title block
dual dim is only for ref. (whoever makes the part is accountable for the primary dim, regardless of the secondary dim) and it's ok to show dual values in dimensions, not in the title block
I have dual values in dimensions on drawing. To be honest I have not seen dual dimension in the title block before. Thank you for the suggestion.
Also look at this.
Thanks Tony. I already have it checked!
Be super careful with dual tolerances.
Depending on how tight your tolerances are, the two tolerances aren't going to be the same unless you stretch out the decimal places.
Diameter .2500" +/- .0005"
Diameter 6.3500mm +/-.0127mm
These are the same, as long as your metric is 4 decimal places.
But if you round the metric to 2 decimal places (like most people do):
Which is:.2500" +/-.0004" (rounded to 4 decimal places).
You just lost 20% of your tolerance.
These are NOT the same thing. Ask any good jig grinder.
My advice: Pick one unit or the other....and if you still need to place the other unit on the print, then make it reference only (which means that the tolerance from the first unit applies).
I had seen both tolerances in title blocks but only one would be primary and other would be secondary/for reference only.
Similar to the picture I've posted above where Inch dimensions/tolerances are primary.
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