Sectioning threaded holes — which line type to include In a section view of a mechanical part that shows the cylindrical view of a threaded hole, which line type should be drawn to indicate the hole axis and properly reference dimensions?

Introduction / Context:
Threaded holes are common features requiring precise location and orientation. In section views, the hole's axis must remain explicit so that dimensions, callouts, and fits are unambiguous.

Given Data / Assumptions:

• The view is a section exposing the cylindrical bore of a threaded hole.
• Standard mechanical drafting conventions apply.
• Dimensions reference the axis for position and depth.

Concept / Approach:
A center line (long-short-long) marks axes of symmetry and cylindrical features, including drilled and tapped holes. Even when material is hatched, the center line clarifies concentricity, helps dimension to the axis, and supports thread note placement (e.g., M10 × 1.5).

Step-by-Step Solution:
Create the section view to expose the bore.Add uniform hatch to cut material, but leave holes unhatched.Draw a center line through the cylinder axis.Attach thread callouts and hole notes referencing the axis.

Verification / Alternative check:
Standards (ASME Y14) consistently show centerlines through holes in both standard and sectioned views; removing the centerline risks misinterpretation of eccentricity or axis alignment.

Why Other Options Are Wrong:

• Hatch line: indicates cut material, not axes.
• Poly line: CAD object type, not a drafting convention for axes.
• Dimension line: conveys sizes/locations but does not replace axis indication.

Common Pitfalls:
Hatching the hole interior, omitting center marks at hole ends, or misaligning the centerline with the true axis.

Final Answer:
Center line