Lance,
I don't need .0001 but probably a total tolerance between the two pieces of zero to .0005 or slightly more would be nice. I just used the turning tool as an example of the fine adjustment that can be gained with a cam type device.
If I were to deal with minimums I could actually work with one inch of travel on the vertical axis and two inches on the y axis(across the table). I want ten to twelve inches of accurate cut the length of the table and at that I would have to manually move the table back and forth and lock it down to position it. That should work pretty well with some good stops and a DRO. I actually need to be able to position pieces up to 32" long but my cuts will be much shorter.
Mike,
Sorry for any confusion. I was running out the door as soon as I finished typing this morning and may have been less than clear. The last thing I want to do is prove that we could put ID numbers on brass or bullets!! The turner just happened to be the tool that gave me the idea since it uses an offset like a cam to get super precise positioning. The necks on my brass turned to an interference fit over the base of my bullets was one component used to put together a string of sub-eighth inch five shot groups at 100 yards with my 6PPC. That is under the world record but of course was not shot in competition.
I don't know if a ballscrew or rack can actually work in ten-thousandths. Everything I have found says accuracy to .0002 I believe but then repeatability to .001, a far cry different! I assume the shorter the more accurate and it may come down to the usual. Will it cost me hundreds of dollars each to get the super accurate conventional short linear motion device? If so a simple circle offset one inch from center will give me two inches of total travel. Seems real feasible when I read I can divide a circle into 2000 parts. Of course I would have to calculate and then calibrate the cams but that should be fairly easy as the plain circles should have linear travel increments.
Of course none of this may be feasible, that is the reason for my original post! I have that itch we all get to start cutting metal and I need to layout the basic design of my machine first.
Hu  |