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DIY Milling Machine Rev Counter for Under £5

As I have a variable speed millling machine without a digital readout (its an Axminster SIEG X2) and wanted a bit more control at the hundreds-of-RPM level than I could get by listening to the pitch of the machine or watching the chuck, some technology was required…

Cycle Computer Rev Counter on an X2 Milling Machine
Cycle Computer Rev Counter on an X2 Milling Machine

The answer was simple and cheap: use a cheap cycle computer that can read RPM (I got a new one for under a fiver off ebay). I carefully dismantled the sensor to expose the reed switch inside, which I taped to the outside of the cover for the top end of the spindle on the X2. I attached the magnet that normally fixes to the cycle wheel to the top of the spindle with a blob of blue-tack so that it ran close to the cover. Thats it! I suppose a better attachment could be achieved than blue-tack but it works fine at the relatively low spindle speeds I am interested in and I just remove the magnet afterwards.