Mill RPM Display

Andrew Carruthers fi ts a speed readout to his Tom Senior mill

As a newcomer to our hobby and with little practical engineering experience I was filled with both trepidation and eagerness in equal measure to jump in and get started. One of the challenges to setting up a workshop is identifying suitable machinery and I soon found myself hankering after a milling machine. Without wishing to spend a fortune, my options are limited to the pre-owned market which brings its own challenges.

I had the good fortune to find a Tom Senior M1 in well cared for condition and as far as I can tell, light previous use. As is the case with older machinery, some of the “bells and whistles” we rely upon are not available. Unfortunately, experience is acquired over time and having broken several cutters, it was suggested by a retired toolmaker friend that I may be running the mill too slowly. Hence this project was born, to set correct rotation speed according to size of cutter and material being machined

Photograph 1 shows the finished display clip mounted on the Digital Readout (DRO). I also wanted the end result to be aesthetically pleasing and in-keeping with the DRO I am installing (which may be the subject of another article) but at the same time be easily differentiated so I chose the Blue display to contrast with the Red DRO display.

This modification is inexpensive, is a quick project to build and delivers valuable information to the operator. Only basic soldering skills and a few readily available parts from either your spares bin or online are required, the display case can be made from offcuts, or if available, 3D printed which is the route I took.

The project can be re-purposed to any other machinery where rotation speed needs to be determined.