Reverse Engineering a Part with a Digital Microscope

Every once in a while you need to make a mating part or a holder for something that already exists. The part in the photo above is a flange from a hammer drill that we are converting into a custom tool, reusing the drill as a motor and gearbox donor. The mating part is the outer wall of the gearbox, so it needs a cover with holes positioned precisely over the gear axes.

Accurately measuring those hole centers the traditional way would take a set of machinist buttons and a good amount of patience. You fit a button to each hole, indicate it, write down the coordinate, and repeat. It works, and it has worked for a century, but it is slow and every transcription is a chance to introduce an error.

In TouchDRO Plus you can use a touch probe and the "Indicate Workpiece" function instead. Besides setting an origin, the indicated points can be added to the sub-datum list, so the coordinates are captured as you go rather than written on a scrap of paper. That is a large improvement over buttons, but finding the center of each hole still means a lot of cranking and careful touching off.

There is an easier way. An inexpensive digital microscope, the kind sold for inspecting coins and circuit boards, can locate part features very precisely, and it costs a fraction of a decent hobby-grade touch probe. The "Recommended Microscopes and Cameras for Milling Machines" page covers the models we have tested and how to choose one.