CNC GD&T Symbol Interpretation 2

Question 1

What does the profile of a surface symbol (an arc with no leader pointing to a plane) control?

Accepted Answer

All points on a surface relative to a true profile

Answer

Profile of a surface controls all points on a feature surface to lie within a tolerance zone defined by two offset boundaries around the true profile.

Question 2

A feature control frame reads: ⌀0.005 M A B. What does the 'M' modifier mean in this context?

Accepted Answer

Maximum Material Condition — tolerance may increase as feature departs from MMC

Answer

The M (circle M) modifier stands for Maximum Material Condition, allowing a bonus tolerance as the feature departs from its MMC size.

Question 3

Which GD&T symbol is used to specify that a hole's axis must lie within a cylindrical tolerance zone relative to a datum axis?

Accepted Answer

True position ⊕

Answer

True position (⊕) locates a feature's axis within a cylindrical (or two-parallel-plane) tolerance zone relative to specified datums.

Question 4

What does a flatness callout of 0.002 mean on a machined surface?

Accepted Answer

All surface points must lie between two parallel planes 0.002 apart

Answer

Flatness requires all points on the surface to fall within a tolerance zone formed by two parallel planes separated by the stated tolerance value.

Question 5

A drawing calls out perpendicularity of ⌀0.003 A on a pin. What shape is the tolerance zone?

Accepted Answer

A cylinder of diameter 0.003 perpendicular to datum A

Answer

When a diameter symbol precedes the tolerance value in a perpendicularity callout, the tolerance zone is a cylinder whose axis is perpendicular to the referenced datum.

(CNC) Computer Numerical Control Machinist Technical Practice Test

(CNC) Computer Numerical Control Machinist Technical Practice Test

CNC GD&T Symbol Interpretation 2