Squareness Tolerance
Squareness Tolerance
(OP)
So nevermind what this says about our QA department that they've asked for a squareness tolerance on this assembly... I would however like to get some feedback regarding how best to tolerance this assembly. Please see the attached image. Below is the suggestion a senior engineer gave my drafter regarding how to control perpendicularity of the assembled frame. I suggested that this is over-toleranced, and redundant as controlling one centerplane with perpendicularity is appropriate, not the two centerplanes twice.

Below is my suggestion for making the frame square. What do you all think? Personally, I'm thinking that the peice parts should be toleranced correctly to control the assembly so this whole assembly tolerance thing is new to me, however, I'm new to this position and am trying to learn how best to process everyone's problematic drawings without throwing everyone into a state of disarray - you know, by following the Y14.5 standard.

Thanks in advance.

Below is my suggestion for making the frame square. What do you all think? Personally, I'm thinking that the peice parts should be toleranced correctly to control the assembly so this whole assembly tolerance thing is new to me, however, I'm new to this position and am trying to learn how best to process everyone's problematic drawings without throwing everyone into a state of disarray - you know, by following the Y14.5 standard.

Thanks in advance.





RE: Squareness Tolerance
Doing more requires knowing what the part mates with, otherwise it's like asking if "20" is the correct answer to an unstated math problem.
RE: Squareness Tolerance
Certified Sr. GD&T Professional
RE: Squareness Tolerance
The four parts that make up the frame are cut from a sort of rubber that comes on a roll. The four pieces are cut to equal length and the assembly needs to be square. They've had some assemblies that have been coming in a quarter inch or more out of square.
I agree, profile of a surface, all around with a value less than the size tolerance. Agree?
RE: Squareness Tolerance
Certified Sr. GD&T Professional
RE: Squareness Tolerance
RE: Squareness Tolerance
Certified Sr. GD&T Professional
RE: Squareness Tolerance
A squareness tolerance would make sense to me if you were willing to have sloppy dimensions otherwise. I.e. your part would the 19.44±0.5, with a squareness tolerance of 0.1mm. Squareness would consist of your sides being perpendicular to each other and equal in length. I do not why you would do that.
As noted above, profile controls size and squareness.
If your part goes inside something, your squareness is required only at MMB. In ASME Y14.5-2009, look in sections 8.3 Tolerance Zone Boundries. There are now several ways to make your profile zone go one way only.
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JHG
RE: Squareness Tolerance
RE: Squareness Tolerance
Who's going to be making these things? Is this going to be sub'd out to a podunk fab shop that's going to only have tape measures and squares? You might want to rethink the idea of applying a profile tolerance.
You could dimension the two sides, then also dimension the diagonals with a more controlling tolerance. I guarantee that's how someone will check 'squareness' if they're making a welded grate, if they had no print.
RE: Squareness Tolerance
On occasion, I have provided rectangular dimensions with some sort of GD&T and I have provided the diagonal dimension across the corners as a reference. This gives a guy with a tape measure a chance to check for perpendicularity. The primary against this is based on people using drafting boards and doing the calculations by hand, possibly with a slide rule.
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JHG
RE: Squareness Tolerance
RE: Squareness Tolerance
Adding the reference diagonal dims sounds like a pretty good idea. So, I'm setting up the bottom surface as datum A, the bottom leg, datum B, left side, datum C, and then using an equal bilateral profile of a surface tolerance (all around - .06 tol.) to control the form and size (with basic dims). They should be able to make a simple fixture with pins or a frame that checks the VC of this assembly and just drop them in to ensure that they conform to the profile tolerance and then they can take some length measurements to assure that it's not too small.