The tachometer suggested by Stan does not need a magnet. I fitted one to my milling machine and also thought that it needed a magnet. After much messing about I was informed that it would read off just the hole that I had drilled for the magnet. It has been working fine for two years now.
Edit.
I have just read the description and it states that it needs a magnet (whoops!) The one that I bought looked the same but did not need a magnet.
Edit.
I have just read the description and it states that it needs a magnet (whoops!) The one that I bought looked the same but did not need a magnet.
NormanV, proud to be a member of MetalworkingFun Forum since Jul 2014.