Hi I am new here and am slowly learning how to build a cnc engraving/router machine.
I have come across a couple of questions as I try to figure things out.
All the projects that use linear rails of some knid do not seem to locate them by any accurate means like dowel pins. They all seem to be located by the threaded bolts that hold them down to the table. Knowing that a bolt shank is not accurate at all, how are people managing to stop the tables binding up all over the place by just aligning the rails on bolt shanks. If all the bolts were loose the rail would be able to move quite considerably. Why are people spending big bucks on rails with accuracy of 5micron for them only to bolt them to a board with no accurate location? How is this working?
I tried to build a machine based on bronze bushes running on silver steel. my thoughts were top let everything move and just slide the table to one end to get the spacing correct on that end then slide the table to the other end of the rails to get their spacing also correct whilst I tightened them up.
Total failure, when the bolts were finally tightened down they always jammed no matter what I did sliding the table. But its runs beautifully when the bolts holding the rails and blocks are loose.
So I tried again using pinned blocks and using a milling machine to drill/bore all the mounting holes to ensure accuracy, and this time it was much better.
But some of the guys withe the ball slides put the rail flapping about on bolts, so how do they go about aligning the rails for alignment and spacing without binding.
This is currently something of a mistery.
Many thanks for any replies.
Dom