The two drawings want different things

An engineering drawing exists so that a part can be manufactured. It is precise, dimensioned and complete, and its reader is expected to know the machinery already. A teaching cutaway exists so that a reader can understand how the thing works. It is approximate, undimensioned and partial, and its reader is assumed to know nothing.

Because the purposes differ, you do not shrink an engineering drawing to reuse it. You mine it for geometry and structure, then rebuild a different drawing around the same machine.

Four moves, in order 1. Engineering drawing dense, dimensioned 2. Pick the section one clean cut 3. Trace the backbone key parts only 4. Teach it part label clear, labelled
Figure 1 — The pipeline. Each stage removes something; the last stage adds back nothing but clarity.

1. Pick the section that teaches

Engineering drawings often already show a section — a place where the part is cut so the inside is visible. Use that as a starting point, but choose the cut for the reader, not for the machinist. A good teaching section passes through the working chamber and the main moving parts, and leaves enough of the object's silhouette that it is still recognisable.

2. Trace the backbone, not the outline

You are not redrawing every bolt. Trace the one route that matters — through the housing, past the piston, out through the port — and simplify the surrounding walls to whatever keeps the shape readable. If two internal features are close together in the real drawing, it is legitimate to shift them apart so the reader can see the gap.

3. Drop the measurement layer

This is where most of the work happens, and it is pure deletion. Remove dimensions, tolerances, surface finish marks, part numbers and section arrows that point at nothing. None of them help a reader understand the principle, and together they are what makes a technical drawing feel hostile.

Keep

  • The cutting plane
  • Working chambers and gaps
  • Moving parts on the main route
  • The overall silhouette

Drop

  • Dimensions and tolerances
  • Fasteners and threads
  • Part numbers and callouts
  • Multiple redundant views

4. Rebuild for teaching

Now you are drawing a new picture, using the cleaned-up geometry as a guide. Apply the site's cutaway conventions — hatched cut faces, three line weights, a faded shell — then add the only layer that was missing: plain-language labels placed where the reader's eye already is. Give each part one name and reuse it in the caption and the parts list.

5. Check it by teaching back

The workflow ends where every diagram ends: hand it to someone who does not know the machine and ask them to describe how it works. Any pause they take is a place where the original drawing's density crept back in. Fix that spot and the cutaway is ready.

Bottom line: mine the drawing for one good section, trace the backbone, delete the measurement layer, and rebuild with labels. The teaching value comes from what you remove, not what you add.