What reverse engineering services involve in practice
Reverse engineering is more than copying a shape. We find out how the part works, which faces it bears against and which dimensions really matter. Only then do we measure and model. A part modelled without understanding its function looks right but rarely fits.
It also helps to know how the part was originally made. Draft angles and parting lines reveal injection moulding, tool marks show milling or turning, and a uniform wall with bend radii points to sheet metal. That knowledge decides how the new model is built and which dimensions were intentional.
The work follows a fixed sequence. The part is cleaned and photographed, datum faces are chosen, dimensions are taken and recorded, and the model is built and checked against the sample. Every dimension gets a source: measured, calculated or assumed. Both you and the workshop then know which dimensions are reliable and which should be checked on the first manufacture.
Measuring tools and methods
Most mechanical parts are best measured with hand tools. A digital calliper has a resolution of 0.01 mm and a practical accuracy of around ±0.02–0.05 mm. Shafts, thicknesses and bearing seats are checked with an outside micrometer that reads to thousandths. Gaps and play are measured with feeler gauges, and the thread pitch is found with a pitch gauge for metric and imperial threads. Before measuring, the part is cleaned of oil, dirt and paint flakes, because a tenth of dirt gives a tenth of error. Each dimension is taken several times and in several places. If the values differ by more than the tool's accuracy, the part is worn or distorted, and that goes in the measurement record.
Radii and fillets are taken with radius gauges. Freeform outlines, such as a curved lever or a handle, we photograph straight from above against a grid with a ruler in the same plane. The image is calibrated in CAD, and the outline is traced with splines and checked against measured points. The photo method typically gives a few tenths to a millimetre, so it is used for shape and not for fits. We describe how to measure and photograph a part yourself in the guide to measuring a part.
3D scanning of complex shapes
A 3D scan captures the shape quickly, especially for cast and organic parts. Accuracy depends on the scanner and is typically between a few hundredths and a couple of tenths of a millimetre. If you already have scan data, we can start straight from it.
The scan itself, though, is only a mesh. It contains noise, holes where the scanner could not reach and reflections from shiny surfaces. We use the mesh as a reference and build a clean model with real planes, cylinders and freeform surfaces on top, just as when we convert STL to STEP. Critical dimensions are still checked against physical measurements if you can take them or send the part.
You get the best result if all important faces are visible in the scan and the file is exported at high resolution. Feel free to send both the raw and the processed mesh, plus photos of the part. That way we can tell real features from scan noise. If you only need a part that fits against the object, such as a holder or bracket, we do not remodel the whole object. The scan serves as a reference and we rebuild only the surfaces the new part has to fit against. You only pay for the area that is actually needed.
Functional dimensions or worn dimensions?
A used part is never exactly as drawn. Shafts wear, holes go oval and plastic shrinks or creeps over the years. If we copy the wear, the new part will be as bad as the old one. So we determine the original nominal size and choose a tolerance that suits the function.
An example: a shaft measures 19.97 mm and sits in a ball bearing. The sensible choice is Ø20 with a tolerance class for a bearing seat, not 19.97 mm. In the same way we work out a hole pattern from measured hole spacings. We also decide whether a thread is metric or imperial, for example M10 with a 1.5 mm pitch or 3/8 inch UNC. If it is unclear, we propose a dimension and flag it, so it can be checked against the mating part.
Plastic parts need extra thought. Moulded plastic shrinks unevenly, and a snap hook may have deformed after years under stress. We therefore compare the part with its mating part and design to what must fit, not to the current shape of the individual part.
From model to new manufacture
The result is a parametric model and a technical drawing with measured and proposed tolerances. With it, the part can be milled, turned, cut from sheet or made by 3D printing. If the original failed because of a weak point, we reinforce exactly that area with radii, thicker walls or a better material. The drawing shows which dimensions are measured, calculated or assumed, so the workshop knows what to check especially carefully on the first manufacture.
Before a batch is ordered, we can print a plastic test part to check the fit against the existing equipment. It is cheap and reveals mistakes in time. You are responsible for having the right to manufacture the part. A spare part for your own equipment, or for a machine whose original part is no longer sold, is normally fine.
Measuring methods and typical accuracy
| Method | Guide value and use |
|---|---|
| Digital calliper | Resolution 0.01 mm, practically ±0.02–0.05 mm – external dimensions, holes and depths |
| Outside micrometer | Resolution 0.001 mm – shafts, thicknesses and bearing seats |
| Feeler gauges | Gaps and play, sets typically 0.05–1 mm |
| Thread pitch gauge | Determines pitch, e.g. 1.25 mm or 13 threads per inch |
| Radius gauges | Inside and outside radii, sets typically 1–25 mm |
| Photo against a grid | Freeform outlines, guide value ±0.3–1 mm depending on size and camera |
| 3D scanning | Shape of cast and organic parts, typically 0.02–0.2 mm depending on scanner |
| Hole pattern | Calculated from measured spacings and diameters, checked against the mating part |
Guide values – accuracy depends on tool quality, calibration and the surface of the part.
What we need from you
- The physical part, or several pieces if it has broken
- Photos from all sides and of how the part is fitted
- Dimensions of mating parts – shafts, holes and screws the part must fit
- Scan data (STL, OBJ or PLY) if you have it
- Any old drawings, even incomplete ones
- How the part is loaded and why the original failed
- Preferred manufacturing method and material, if you know
Typical projects
- Pinion for a machine without documentation
- Cast bracket to be machined instead
- Plastic lid for an older appliance
- Adapter piece between two existing components
- Scanned shape to become clean CAD
- Worn plain bearing to be drawn with the correct fit
- Classic vehicle part where only a broken piece remains
- Paper drawing to be checked against the real part
- Lever or handle with a freeform shape
What affects price and lead time
- Number of faces and how complex the shape is
- How much is worn or missing
- Tolerance and fit requirements
- Whether a toleranced drawing is included
- Whether a test print and adjustment are needed
- Whether the part is sent to us or measured from photos
- Whether the whole object is modelled or only the surfaces a new part must fit against
What you get
- Parametric CAD model with documented dimensions
- Drawing with measured and proposed tolerances
- List of assumed dimensions to check
- STEP, STL and DXF as needed
- Test print for fit (optional)
Frequently asked questions
Do I have to send you the part?
Not always. Simple parts can often be modelled from photos with a ruler in the picture and a few dimensions you take yourself. For fits, threads and complex shapes, the result is more reliable if we have the part.
Do I get the original part back?
Yes. The part is handled with care and returned once the model has been checked. We never take apart or cut parts without asking first.
Do you copy the wear as well?
No. We determine the original nominal size and set a tolerance based on the function. Worn and uncertain dimensions are flagged so you can see what has been assumed.
What can be done when a part has broken into several pieces?
The pieces are often enough. We measure each piece, fit the shape together in CAD and complete what is missing from the mating parts. The fracture also shows where the design needs reinforcing.
Can any part be copied?
You are responsible for having the right to manufacture the part. Spare parts for your own equipment are normally not a problem, but protected designs made for sale may be.