Team 303 has had a shop bot for 2 years now and we are starting to get comfortable with it. We have the larger buddy and bought the 8' power stick.
1) Tolerance: Center to center tolerance is quite good. We have made a few gearboxes in 1/4 inch plate, in addition to a lot of c-c chain runs and gear-driven mechanisms which require good tolerance. +-0.001? Probably not. Id say the tolerance for c-c is 0.003. Most of our gearboxes have come out perfect but we have had some super tight chain runs along with a few which are a little loose. But IMHO, 0.003 is enough for most any FRC application. The sb desktop page boasts a resolution of 0.00025”. I would be surprised if that was true. One thing to mention is that because of bit flex and I think the buddy's tolerances, the diameter of a pocketed hole always comes in about 0.005 undersized. To compensate we oversize a tad in cad then ream holes for bearings.
2) Box: We have machined tons of wood for prototyping, 1/8" sheet aluminum, 1/4" aluminum, 1x1 box, 2x1 box (both dimensions) and 2.5 x 3 box. The wood is amazing, with just a few screws into the wasteboard the buddy will fly through wood. The sheet aluminum is just as easy. We screw down the sheet in the corners, drill any holes and put more screws in them, then we profile it. As for box, originally we tried holding the box to the wasteboard with wood screws and washers but it was not nearly solid enough and a dangerous and bad idea. Next we tried screwing two vices down to the washboard and that was okay. It took a while to get the vices perfectly square but we eventually got the hang of it. In this offseason we built a more elaborate setup with a wasteboard and two vices off to the side just to keep the vices out of the way of the board. We are really liking this setup.
I am now just realizing the desktop doesn't come with a wasteboard, but rather an aluminum deck and that you plan to get the spindle when we have the router. I cant speak for the spindle but I highly recommend permanently attaching a vice or two to your aluminum bed along with a wasteboard as it will make sheet and box much easier. Once you spend a while getting them perfectly aligned, it becomes a breeze to machine box. I highly recommend the 3 axis zeroing plate:
https://store.shopbottools.com/colle...ant=7825832513
It makes finding the edge of box super easy, plus it tells you if your piece isnt aligned with the machine.
Just a few final notes: 18x24 is pretty small. If you plan on doing primarily gearboxes then you will be fine but we have made drive rails and longer box cuts with great success with the longer bed. Just keep the desktop max in mind. Be prepared to break a bit or two when learning. We use these bits:
http://www.amanatool.com/products/cn...uter-bits.html
Mostly with ¼ cutting diameter. We also have a 1/8th which we use to drill 10-32 holes in gearboxes. In comparing it to a mill, it will be easier to do box on a mill but it is certainly possible to do it on a shopbot. Another good tool to have is this:
https://www.amazon.com/Fowler-54-575...ds=edge+finder
It helps when trying to manually find zeros or if you need to shift a long piece of box and zero with a cut in the middle
Wow I didn't expect to write this much. If you have any questions feel free to ask here or PM me.