Customer Rejecting Part for Basic Dimension

thehovie

Registered
Customer is rejecting part because it is not 63.5 mm long. While I'm new to the industry, I know that this is a "basic dimension" and does not have a tolerance. Without a tolerance I don't know how to make this a conforming part because I know there is no way for us to achieve a perfect part that is 63.5000 mm long.

Is there an implied tolerance such as +/- 0.125 for this dimension?

Is the customer right to be rejecting this part for this dimension?

Should the drawing contain other information about the length?

I can't post links yet, to see the drawing visit:
 

Cari Spears

Super Moderator
Leader
Super Moderator
Basic dimensions do have tolerances; they are controlled by feature control frames somewhere else on the drawing. In this case, the basic dimension "63.5" is controlled by the perpendicularity and profile callouts.
 
Seems to me that this should not be a basic dimension. Basic dimensions are used to represent the theoretical location of a feature. This is not the case here since this is a simple length. You as the supplier should be providing tubing that is at least 63.5 mm long. I would think that this is what your customer is expecting.
 

Michael_M

Trusted Information Resource
You will probably need to take a geometric tolerance class to learn more but for a 'very' basic idea, the 63.5 length would be 63.5 ±.75 (basically ± half the profile). Be careful and this is why I highly suggest getting a class. There are symbols that can change the profile to make it read only one way +X/-Y. Additionally, the profile call out also restricts parallelism.
 

thehovie

Registered
What is the actual length that they're concerned about?
Customer was receiving some 30-50 mm long, rejected them and said they are supposed to be 63.5. Obviously 30-50 mm is not a quality part, but as I review this case I'm trying to find out what the exact tolerance is so that we can sort them.

Basic dimensions do have tolerances; they are controlled by feature control frames somewhere else on the drawing. In this case, the basic dimension "63.5" is controlled by the perpendicularity and profile callouts.

You will probably need to take a geometric tolerance class to learn more but for a 'very' basic idea, the 63.5 length would be 63.5 ±.75 (basically ± half the profile). Be careful and this is why I highly suggest getting a class. There are symbols that can change the profile to make it read only one way +X/-Y. Additionally, the profile call out also restricts parallelism.

Would the length basic dimension of 63.5 have a tolerance that combines additively half of the profile and half of the perpendicularity? Or would the tolerance for the 63.5 be one or the other?
 

John Predmore

Trusted Information Resource
The GD&T drawing depicts tolerance zones relative to a geometrically ideal part. Basic dimensions on the drawing define the geometrically ideal part. Each geometric tolerance, such as perpendicularity or profile callouts, serves as a constraint on allowable part dimensions. Whichever constraint is tighter will serve to constrain, so there may not be a simple answer. I agree with @Michael_M , GD&T can be a complicated subject, and for a fuller understanding than we can provide here, you should take training.
 

thehovie

Registered
The GD&T drawing depicts tolerance zones relative to a geometrically ideal part. Basic dimensions on the drawing define the geometrically ideal part. Each geometric tolerance, such as perpendicularity or profile callouts, serves as a constraint on allowable part dimensions. Whichever constraint is tighter will serve to constrain, so there may not be a simple answer. I agree with @Michael_M , GD&T can be a complicated subject, and for a fuller understanding than we can provide here, you should take training.

Ok, I will look into classes. For this instance, I'll take Michael's tolerance of 63.5 +/- 0.75. Thanks to everyone for your help.
 

Michael_M

Trusted Information Resource
Would the length basic dimension of 63.5 have a tolerance that combines additively half of the profile and half of the perpendicularity? Or would the tolerance for the 63.5 be one or the other?

To keep it fairly simple. The overall length of the part is 63.5 and would have a tolerance of ±.75 (quick calculation based on the profile call out). Again, there is a bit more to it than this, but this gives a good starting point.
 

Cari Spears

Super Moderator
Leader
Super Moderator
Each end is +/-.75, so double that for the overall tolerance.

With the information given here, I would do this:

Verify that each side is perpendicular to A within 1.5.
Set it on one end on a surface plate, and use a height gage and indicator to ensure that the other end is within 63.5 +/-1.5.
 
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