Spindle load indicator

I`m used to having a load indicator on the mills and lathes I work with, so I decided to assemble one for the Proxxon IBS/E, Dremel 3000 or other 100-200W spindles that I plan to use with my Stepcraft machine. It is connected between a wall socket and the tool. Maybe it would be better to mount it between the controller and the motor, but the first option is easier to do and more convenient when changing spindles. Besides I plan to use full revs most of the time.

The parts are available at electronics shops and regular sellers of construction materials. The most expensive component is the AC ammeter. I got the biggest one available at the time, because bigger is usually cheaper when it comes to electronics at least. Chose the dial indicator because digital ones are sometimes difficult to read in case of alternating loads. I haven`t checked the accuracy of the indicator and I`m more interested in relative indications. On my first part milling the highest load was achieved when cutting a groove into birch plywood at 600mm/min feed, 2,15mm cutting depth with a 2 flute fishtail carbide milling bit. The indicator showed about 0,3A that translates into 66W or 66% of max power in case of IBS/E. Don`t take this as a recommended setting.