Tolerances of a 'Basic' Boxed dimension
Tolerances of a 'Basic' Boxed dimension
(OP)
Please could you advise me here. My understanding is that a dimension in a rectangle box is theoretical and without tolerances (other than those defined in the drawing border)
I have, however been approached by another take on this. Please see the attached sketch.
I'm told that the 27mm dimension 'becomes' 27 +/- 0.1 because of the positional control on the hole... Is this correct? (NB Datum G is the left leader line of dimension 27)
In my sketch I've indicated how I read the tolerance for the dimension 27 i.e. +/- 0.23 per the default drawing border control.
Any advice is greatly appreciated here.
I have, however been approached by another take on this. Please see the attached sketch.
I'm told that the 27mm dimension 'becomes' 27 +/- 0.1 because of the positional control on the hole... Is this correct? (NB Datum G is the left leader line of dimension 27)
In my sketch I've indicated how I read the tolerance for the dimension 27 i.e. +/- 0.23 per the default drawing border control.
Any advice is greatly appreciated here.
Solid Edge; I-Deas 7 to 12; NX4 & currently NX5.





RE: Tolerances of a 'Basic' Boxed dimension
Assuming you are using ASME Y14.5M(1994) the standard used the most in the US, then the default title block tolerance would apply to a dimension without a tolerance that is NOT basic. If a basid dimension is use then there MUST be a geometric control (such as the one you have shown) to state the tolerance. Ths symbol you have shown gives the tolerance realtive to direction dim 11 controls (I assume that this is a vertical dimension and is basic). The 27mm basic dimension is based on your drawing without a tolerance, it could be anywhere on that section of the part and still meet the print. I suggest you study the standard for more information.
Note this analysis assumes that dimension 11 gives a vertical distance from datum G. The feature needs to be dimensioned relative to the datum(s) with basic dims.
Picky checker point, remove the first space from the "2 x Ø..." and use a capital X, the standard shows more that one use for X, with the space it could be argued that you have a 2mm X Ø6.75mm slot as opposed to 2 Ø6.75mm holes. The standard does state that there should be no space between the number "2" and the "X".
Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services
www.infotechpr.net
RE: Tolerances of a 'Basic' Boxed dimension
RE: Tolerances of a 'Basic' Boxed dimension
If it (the 27mm dim) were not in a box, then I take it the drawing border tolerances would then apply...
NB I thought that the direction of the tolerance was cylindrical i.e. all around not just vertical, I am understanding that correctly?
Solid Edge; I-Deas 7 to 12; NX4 & currently NX5.
RE: Tolerances of a 'Basic' Boxed dimension
If there was a diameter symbol in front of the .2 tolerance, as I think there should be along with another basic dimension, then you would have a cylindrical tolerance zone with a diameter of .2 and a height equal to the length of the feature. This tolerance zone would control the both location and attitude (i.e. tilt) of the simulated axis of the hole.
RE: Tolerances of a 'Basic' Boxed dimension
Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services
www.infotechpr.net
RE: Tolerances of a 'Basic' Boxed dimension