Box Dimension on a Mechanical Drawing

boxed dimensions are theoretically perfect numbers. tolerances are derived from the GD&T tolerance frame that is associated with the dimension. boxed dimensions do not experience tolerance stackup when there is more than one dimension in line. each dimension is mathematically perfect.

for instance, say you have a hole that is dimensioned using conventional toleranced dimensions in both x and y coordinates. say for instance that the tolerances on those two dimensions are +/-.005". you end up with a square target zone .010" on a side.

if that same hole were dimensioned as a bolt circle diameter and an angle, your tolerance zome is a truncated pie shape. but if you used basic dimensions with a true position symbol and .010 as the tolerance in the box, regardless of whether it was a bolt circle/angle or cartesian coordinates, the target zone is a circle .010 across.

Basic dimensions must be refereced to datums. Generally you have a datum for each axis in which basic dimensions are refereced from. datums are NEVER on a centerline. this is a VERY COMMON error. Datums are always on a surface. Usually a planar surface, but they can be on a cylinder as well. the one exception is cylinders. when you put a datum on a cylinder, you are assumed to have two perpendicular planes that intersect on the CL of the cylinder. so you can get both an x and a y coordinate datum off a single datum reference.

there are a number of different GD&T frame symbols that you might find. I would suggest you pick up a copy of Geometrics III. it is a pretty good primer on GD&T.

Check ANSI Y14.5.

Ahhhhhhh ...... That'll be $169.00 sir.

Best you find a book on the subject. Will be a whole lot cheaper and easier to read and understand.

Ed Weldon

Ahhhhhhh ...... That'll be $169.00 back to you sir.

Best you don't comment on something you know nothing about.

Maybe you should buy a book

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davidv123

It is depends on your applications where you used which used it is function it is outer box or inner part or covering sheet any pl replay i will draw and send it you

it is a geometric tolerance......we can measure and advise the best to to manufacture these componets....http://www.alnoproductservices.com.au/

Anthony