FILENAMES: milspeed.jpg DESCRIPTION: This is a picture showing a DC motor drive installed on a mill-drill. Posted by John Stevenson . John provided the following description: ================================================================= On Thu, 06 Jul 2000 23:43:07 -0700, appsman wrote: >On my Grizzly g1008 mill, it seems the motor mount does not have >enough swing to allow the lowest speed belt position. The motor >bumps up against the frame and so won't get any closer to the >idler. The motor-idler pulley spacing has to be shorter so I can >get the belt on. I finally forced it there, but I bet the >bearings are not happy. It's tight! Does anyone know if I am >doing something wrong? It doesn't seem right that the motor is >bottoming out against the frame. > >After this much sweat just to get 200RPM, I'm ready to spend $ >to make this go away with a 3-ph motor and VFD. What's the >cheapest way to get this done with reliable hardware? Any >guidance would be appreciated. Thanks. > I had exactly the same problem with one of the early Mill/Drills My problem was I needed heavy cuts at low speed and the wrap round on the belts in the low ratio was that small that I had to have the motor far too tight. I resolved this by switching onto tooth belt drive to prevent slip and changing the motor to a 240v DC unit. I used a three speed tooth belt setup and a DC speed control to adjust speed between the ratios. This was about 17 years ago before VFD's became popular and cheap. The DC motor was the only cheap way to go. In retrospect if I now had to do this again I would only use a two speed belt reduction and go with 3~ and a VFD. Having said this I still have the machine and it's still in everyday use.I have posted a picture on the drop box at www.metalworking.com under the name Milspeed.jpg and this file as Milspeed.txt Also visible in the photo but not too clear is the setup to provide power feed to the quill. If any more details are required I can supply them.