GD&T

Question 1

What is a size feature?

Answer 1

Distance between two opposed parallel surfaces, a cylinder, or a sphere.

Question 2

What are the three basic concepts that define the limit of size?

Answer 2

All two-dimensional measurements must be within the stated limits of size; a variation in form is allowed between the least and maximum material sizes; and there is a perfect form boundary at maximum material condition.

Question 3

What advantage does MMC have over LMC?

Answer 3

Because there is a uniform boundary at MMC a gauge can be used to check compliance.

Question 4

What is does the first section in a feature control frame contain?

Answer 4

It always contains one of fourteen different geometric control symbols.

Question 5

What does the second section in a feature control frame contain?

Answer 5

It contains the tolerance information, including tolerance zone shape, size, and modifiers if any.

Question 6

What does the third section in a feature control frame contain?

Answer 6

The third section contains datum references.

Question 7

How do tolerances change depending on how close to the respective MMC or LMC modifier the size feature is?

Answer 7

At LMC or MMC the tolerances are tightest, and the tolerances relax the further from their respective modifier they are.

Question 8

What is the tolerance zone of a flatness callout?

Answer 8

Two parallel planes.

Question 9

What is a generally conservative flatness capability for manufacturers?

Answer 9

0.0005 per inch of surface length.

Question 10

When should a datum not be attached directly to the size feature?

Answer 10

When the feature itself requires machining to a specified tolerance before being utilized as a datum the datum should be attached to the feature control frame.

Question 11

What is the tolerance zone of a straightness callout?

Answer 11

Two parallel lines evenly spaced from the theoretically perfect line, two parallel planes evenly spaced from the theoretically perfect plane, or with the addition of a diameter symbol a cylinder with the theoretically perfect straight line as the cylinders axis.

Question 12

Why shouldn’t the straightness callout be used?

Answer 12

It does not provide a reference nor orientation for inspection.

Question 13

What is a unique property of the straightness callout?

Answer 13

Straightness allows the form of the part to to exceed perfect form boundary at MMC.

Question 14

What is the tolerance zone of the circularity callout?

Answer 14

Concentric circles.

Question 15

What is the tolerance zone of the cylindricity callout?

Answer 15

Concentric cylinders.

Question 16

What is the intent in setting datum’s?

Answer 16

The restriction of degrees of freedom.

Question 17

What risk is taken when using an entire surface as a datum?

Answer 17

Manufacturers may use small widely spaced supports, which may result in higher spots elsewhere on the surface (the actual datum design intended) to through off tolerances.

Question 18

Which feature callout is parallelism related to?

Answer 18

Parallelism is a straightness callout but the tolerance zone is related to a datum.

Question 19

Which feature callout is perpendicularity related to?

Answer 19

The perpendicularity callout is related to the straightness callout, but the tolerance zone is related to a datum 90 degrees to the feature.