Reverse-engineering a caliper in Creo
Parametric reconstruction from the disassembled tool
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Rendered CAD view of the reconstructed vernier caliper
- Context
- Mechanical CAD, DTU
- Year
- 2025
- Role
- Modelling
- Team size
- 2
- Tools
- PTC Creo · Parametric modelling · Datum planes · Axis patterns · Assembly constraints
- Contribution
- Team of 2, we each modelled the complete caliper independently
A full parametric reconstruction of a vernier caliper, modelled in PTC Creo from the disassembled physical tool, four parts, assembled and rendered.
The build
Shaft, slider, screw and thumb knob, each from sketch and extrude, with extrude-cuts for the depth rail and the screw holes. The caliper's characteristic angles had to agree across parts, so features were mirrored on the right and front planes to keep them consistent; datum planes carried the angled gripping tips, and an axis pattern produced the grooves on the knob. Assembly was done by constraining the screw cylinder to its hole and mating the faces.
The irony of the brief
The caliper had to be taken apart to be measured, which meant measuring a precision instrument with an ordinary ruler. Getting the numbers exact was the hardest part of the whole job, and having a second, digital caliper on the bench is the first thing I would change.
What went wrong
Partway through, several parts silently switched from millimetres to inches. One of them could not be converted back without breaking its downstream features, so the final drawing is annotated correctly but wrong on scaling, material and weight. Creo constrains far more strictly than Fusion, sketch mode demands closed profiles with no stray lines, and cancelling an extrude drops you out of the sketch entirely instead of back into it. Learning to work with that, rather than against it, is what I carried into the next CAD project.
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Creo extrude and revolve features on the thumb screw, with the knurled pattern highlighted
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Creo geometry pattern editor showing the slider part patterned in two directions
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Fully dimensioned Creo sketch for the second caliper part