Don't use this kind of vise. It's garbage, doesn't hold things well, you will break it, and it's very hard to get things to settle in flat because when you tighten it one side lifts up. I expirimented with using ATF for machine fluid. It was better than nothing, but also not the right answer.
Friday, March 4, 2011
The next weak spot was that we were relying on the motor's bearings to take thrust forces being transferred back down the ballscrew. This works up to a point (although it puts some stresses on them that will shorten their life), but once you exceed a certain amount they will push back and forth about 1/8". Most solve this by having a mounting block with thrust bearings holding the ballscrew end, and then using a spider coupler between the motor and the ballscew to sort for misalignment.
And that would probably be prefereable, but I didn't design for it and had to get creative. So above you can see one end of my motor (fortunately it has shafts on both ends) with a stop I lathed out holding a thrust bearing against the motor casing. There is another one on the other side doing the same thing, trapping the shaft in place. This was actually completely effective, and likely how I will do things in the future too. It saves on parts so long as you have some alignment adjust-ability in your motor and/or ballnut mounts.
And other reasons I adore the English language. I am going to try to catch up on the progress the machine has made, because a lot has happened lately. The results are that we have a darn good working machine (as you can see in the previous video) and it's only getting better as we learn.
First, once we put the spindle on some new flaws became apparent. We were getting a lot of chatter, the source of which we determined by means of high speed film (thank you modern DSLRs). The rails on Z were flexing, the whole frame was flexing, and all of that was leading to problems. This wasn't apparent with the router tool because it was taking off so little at a time (and creating a ton of heat, and taking forever).
So I replaced the Z rails with the next size up and triangulated the frame, adding a truss to the back of one mounting beaml: