I have a 1953 Northfield 12HD jointer. It has been a great machine with one exception. I got it with a 5 hp three phase motor. I swapped it out with a new 3 hp Baldor single phase motor and Furnace starter. It works fine except on shut down. Something happens to the motor that causes a brief shutter that throws the belts. The folks at Northfield suggested that this is characteristic of single phase motors. They also recommended I use double 3/8" belts when I did the motor swap. Once running the belts work fine. I asked them if I could switch to 5/8" belts and pulleys in order to stop the belts being thrown at shut down. They are suggesting against it. I don't remember why. They are now suggesting I put the original 5 hp/3 phase motor back on with a vfd. I wouldn't mind doing this, but I don't know the condition of the 68 year old motor, a proper name brand vfd will cost close to $1,000.00 with tax and shipping, and the vfd will require a 50 amp/220 volt circuit, which I am capable of providing, but it's a big job. This seems to be a very expensive and labor intensive way of preventing the belts from being thrown. The current 3 hp motor works great and I have yet in all the years I have owned the jointer, been able to bog it down. I've adjusted the belt tension and checked the pulley alignment. The distance between the motor shaft and the cutterhead shaft is 37 1/2 " OC, making for long belts. Any suggestions? What about idler pulleys to reduce the flex on the long stretch of belts?