Re: cnc conversion of jet 9 x 42 knee mill

>
> HELLO TO THE GROUP, I,VE JUST JOINED THIS GROUP. I OWN A JET JTM-2
> KNEE MILL THAT I AM GOING TO CONVERT TO CNC AND WOULD LIKE TO GET A
> GENERAL OPINION FROM THIS GROUP BEFOR I ACTUALLY PUT OUT THE MONEY FOR
> THE PARTS. FOR STEPPER MOTORS 1290 OZ/IN FOR X AND Y AND 600 OZ/IN
> FOR THE Z AXIS "I WILL DRIVE THE QUILL ". X AND Y WILL HAVE 2 TO 1 BELT
> DRIVE, NOT SURE ABOUT THE RATIO FOR THE Z AXIS YET. THE MOTORS ALONG
> WITH GECKO 203V DRIVES WILL COME FROM HOMESHOPCNC, NOT SURE ABOUT
> WHICH BREAKOUT BOARD YET. I WOULD APPRECIATE ANY AND ALL
> OPINIONS
> THANKS

I did a Jet knee mill just a bit smaller than yours, 8x36 table.

I think you might be to big on the X and Y motors- excess torque but may
limit the speed. Id use about 700 oz-in

My strong advice is to move the knee not the quill. Once you have used a
powered knee you will wonder why anyone would ever do a quill. Having
the quill free to do tool changes, or to re-set tool height is very handy.

I used a 1200 oz-in motor with belt drive to the screw. I initially put
the motor on the crank handle, but later removed that shaft and put the
motor under the table- it fits very well with a nice short belt.

I used Geckos, and PMDX breakout boards.

I did have some trouble with lost steps on the knee, but that was solved
by switching to the Smoothstepper instead of par port. I have now runs
several jobs that took hours- one a 3" taper pipe thread, that all came
out perfect.

There are some photos of my conversion on my web site, plsntcov.8m.com
although I have not updated it with the knee motor move.

ron ginger