Many replacement and custom parts are ordered without any engineering drawings — because reverse engineering from a sample or photo works well. Here's how the process works and how to make it accurate.
What reverse engineering means
Reverse engineering is recreating a manufacturable part from an existing object rather than from original design files. For metal parts like exhaust pipes, hoses, brackets, or housings, the manufacturer measures the sample, captures its geometry, and produces a new part that matches.
What to provide — best to workable
- Best — the physical sample or the old part; the most accurate input
- Good — clear photos from several angles with a ruler or caliper for scale, plus key dimensions
- Workable — a hand sketch with critical measurements (length, diameter, bend angles, connector type)
The measurements that matter most
For piping: overall length, outer diameter, wall thickness, bend angles and radii, and connector or flange type and size. Note the material if you know it. Telling the manufacturer which dimensions are critical (must match) versus reference helps them prioritise.
How the process works
- Measure and capture the geometry (calipers, gauges, sometimes 3D scanning or CMM)
- Confirm the material and tolerances
- Produce a sample for your approval
- Adjust if needed, then move to mass production
Tips for an accurate result
- Send the actual part whenever possible
- Photograph against a plain background with a scale reference
- State the operating environment so the right material is chosen
- Approve a sample before bulk production
Frequently asked questions
Can a worn or damaged part still be reverse-engineered?
Usually yes, although heavy wear may require some engineering judgement to restore the original dimensions.
Is reverse engineering less accurate than working from drawings?
With a good sample and a sample-approval step, it is very accurate.
Who owns the resulting part?
A reverse-engineered replacement of your own part is yours. Avoid copying a third party's patented design.
Related reading
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