Understanding Cuts and Sections in Technical Drawing

Posted on Mar 20, 2025 in Mechanical Engineering

Cuts and Sections in Technical Drawing

Court: Is the artifice by which, in the representation of a piece, we remove part of it to clarify and make easier its representation and dimensioning.

Section: Intersection of a cutting plane with a part (the area indicated in red). As seen when rendering a section, unlike a cut, it does not render the rest of the piece that is behind it. Whenever possible, we prefer to represent the section as it is a clearer and simpler representation.

Types of Cuts

  1. Total Cut: Is produced by one or more planes, fully experiencing the piece, leaving only the boundary edges in the exterior view (Figures 21 and 22).
  2. Half Cut (or Cut to a Quarter): Used in parts having an axis of symmetry. It shows half of the part in section and half in external view. In this type of cut, hidden edges are not represented, so that the representation is clearer. Sometimes an edge coincides with the axis of symmetry; in that case, the edge prevails. In this type of cut, whenever possible, narrow the exterior elements of the piece on one hand, and internal elements on the other.
  3. Partial Cut (or Bite): Sometimes we just need to represent small interior details of a piece. In such cases, a full cut or half cut is not needed, and this type of cut will suffice. The partial cut shall be demarcated by a slightly sinuous, thin line.

Sections without displacement: These are represented bounded by a thin line.

Rotated Sections: These are represented bounded by a thick line.

Successive Rotated Sections: Displacement of the section can be made along the axis.

Rules for Hatching in Cuts and Sections

The surfaces of a part affected by a cut are highlighted by parallel hatching lines, whose thickness is the thinnest of the series used. We set the following rules for carrying out the hatching:

  1. The slope of the hatching is 45° to the axis of symmetry or main contour of the part.
  2. The separation between the hatch lines will depend on the size of the piece, but should never be less than 0.7 mm and not more than 3 mm.
  3. In large parts, hatching can be reduced to an area that follows the contour of the surface to be hatched.
  4. In cases of partial cuts or bites, the separation between the sectional area and the rest of the piece is indicated by a thin, freehand line, and should not coincide with any edge or axis of the piece.
  5. The different hatched areas in one piece, belonging to the same cut, shall have the same angle and separation. The same hatching will also remain when it comes to different cuts on the same piece.
  6. In parts affected by a cut by parallel planes, the same hatching will be used and can be moved in the separation line for greater understanding of the drawing.
  7. In sections on representations of sets, the different parts are hatched by modifying the inclination of 45 degrees, and when unavoidable, the separation of the hatching will be varied.
  8. Thin surfaces are not hatched, but are blackened. If there are multiple contiguous surfaces, a small gap would be left between them, not less than 0.7 mm.
  9. Appropriation levels should be avoided on hatched surfaces. If they must be recorded, hatching will stop in the area of the dimension number, but not the arrows and dimension lines.
  10. No hidden edges are drawn on the hatched surfaces of a cut. This is only permissible in exceptional cases, if unavoidable, and if it contributes decisively to the reading and interpretation of the piece.