I am thinking about adding a spindle tachometer with a SFM calculator to my lathe while I have it down for a little refurbishing. I have found two different ones by searching on the net. Here are a couple of links to the different ones I have found.
For some reason I think this one is out of the UK, but I can't find the info back that makes me think that.
I think this is the same unit for a little less money, if the price is current.
LittleMachineShop.com - Tachulator Tachometer & SFM Meter
I am wondering if anyone has any experience with any of these units. Or if you know of similar units please let me know about them.