[Dylwad]

Very nice!

You could have also used a phase tach sensor to get your rpm signal, they cost $3 and are very reliable.

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[Mad Welder]

Love the progress very innovative.....looking forward to the finish and an engraving video....and again thanks for sharing

[abfa9358]

The project is finished! Here are some pictures. The tacho uses a pic to time between rotations of the motor body, seems to work well, but took at lot of fiddling to get the interrupt routine working well (mainly due to my inexperience).
Here's link to the video

[abfa9358]

This is a bit of a sad follow up to this thread. The high speed spindle has been used in anger to create a memorial for our old cat who passed away recently. I ran a carbide engraving bit at 11krpm DOC 0.004 Feed 20ipm, the plate took around an hour to cut.