Dimensions in brackets

Question

Hi all, I have an engineering drawing and 1 of the 12 dimensions are in brackets, can someone tell me what this means?

Thank you.

Answer 1

I think that means it is an unseen dimension. So it is covered up in that view of the object.

Answer 2

This indicates that the dimension is either redundant or not critical. correct.

Answer 3

usually bracket signify dual units i.e. metric and imperial

Answer 4

I think it is used to reference hidden or sectioned parts of the diagram.

Answer 5

Dimensions in parenthesis (dim) are reference dimensions.  This indicates that the dimension is either redundant or not critical.  Some times brackets [dim] are used.

Answer 6

I think it's a redundant dimension.

In manufacturing you can never machine parts to an exact measurement. The redundant dimension is used to allow a little "slack", which is allowed to be taken up by these errors.

Say you have a series of 10 cylinders which fit next to each other in a line. You want the cylinders to have a length of 100mm , but you can only machine the length of the cylinders to accuracy of +/- 1mm. In the largest case the total length is 110mm, The smallest case would be 90mm. In you need to control the length (to +/- 1 mm) you need another "cylinder" on the end. here it would be somewhere between 10mm and 0mm in length, depending on how much error has crept in to the machine of the other components