Start with the part in your hand
A part breaks, or a customer brings in an old component with no paperwork, and you have to remake it. You do not need the original drawings to do that. Everything you need is in the part itself: the shape is visible, and the real sizes come off a pair of calipers.
Take the key measurements first. Overall length, width and thickness, the diameter and position of any holes, and any feature that has to fit something else. Write them down. These are the numbers no photo and no AI can guess for you, and they are what make the difference between a sketch and a part that actually fits.
The shortcut: photo first, measurements second
Modelling a part from scratch in CAD is slow. The faster path is to let AI read the geometry from a photo and lay out the drawing, then feed in your caliper readings:
- Photograph the part straight on. Fill the frame, keep the camera square to the face, and use even light so the outline is crisp.
- Let the AI lay out the views. It reads the outline and proposes front, top and side views with dimension lines already placed.
- Enter one real measurement. One known caliper reading sets the scale for the whole drawing, and the rest of the dimensions follow from it.
- Confirm the features that matter. Check the holes and mating faces against the part, add tolerances where it has to fit, and export to DXF, DWG or PDF.
What to watch for
Worn or damaged parts lie. A bushing that has worn oval, or an edge that has chipped, will give you a measurement of the broken part, not the part as designed. Measure across unworn surfaces where you can, and use round design intent (a shaft that mics at 11.97 mm was almost certainly meant to be 12 mm) to recover the original numbers.
For the longer walkthrough see our blog post on reverse engineering a part from a photo, and getting dimensions from a photo covers how accurate that scaling step is. Once the drawing is done, making it ready for CNC machining is the last step before you send it out.