Well, I just finished upgrading my PRT Alpha with the 7.2 motors. Many thanks to Frank Leinbach for his instructions, Brady Watson for his recommendations on ramp speeds, slow corner speeds, etc., and Frank at ShopBot Support for getting me over a few glitches with the 3.5.5 Software.

All I can say is that I am more than impressed. Yesterday I did a bunch of test cuts to see how accurately I was cutting. I used a new Centurion .25 in. down spiral in MDF. I cut a number of 1, 2, and 4 inch squares .125 in deep. Feed rate was 240 in/min and RPM was 14,000 for all cuts. I cut some in one pass, both climb and conventional. Others I cut with an initial roughing cut offset .02, followed by a finish pass. The most any of the squares were off was .007 - .008 on one 4" square using a climb cut in a single pass.

With a rough and finish cut the squares were off .001-.003 in each axis.

I did measure the bit prior to starting, and it was actually .245 in., so I used this as the actual cutting diameter of the tool.

I think if I tweaked the feed rate and RPM's I might even do a little better.

Needless to say, I'm impressed, not to mention overjoyed not only with the accuracy, but with the speed and smoothness. Were it not for this forum, and the Camp ShopBot I attended in Kitty Hawk, it's doubtful that I would have done this upgrade. Many thanks again to everyone who posts here.