Hi. I'm allmost done with the CNC machine itself, but I have some questions about it which I hope some of you guys could answer.

First of all I would like to tell about my setup. I'm using 3 500oz-in steppers on all axis. I also have ballscrews with 16mm x 4mm pitch and adjustable backlash (kind of special nuts that you put in a block and tighten up to get rid of all backlash in it). I also have preloaded ball bearings on all axis and I run the steppers with 3 G201's at 36V @3A. I have never tested it above 60ipm, and I dont think I need to. It's fast enough for me.

It's also converted to belt drive just to make it a little more quiet.

Now for the questions. How tight are the gibs on your machine? I tighten them so much that I cant move the table by hand (pushing and pulling.. Not using the screw). This is to ensure that the table doesnt move before all the backlash has been compansated for. This means that I can jog the machine with 0.0004 increasements back and forth with no problem. This does however cause some problems. From time to time I might loose a few steps which is bad. And so my next question will be. Should I make the gibs out of steel with nylon inserts to reduce friction and to get the same pressure over the whole length of the gib? This way I can tighten them as much as I want without any problem. Have anyone else done this? Is it a good idea?

Next question. How much should I preload the ball bearings? I have preloaded them as much as I can, but it gets kind of hard to turn the ballscrews, and i guess I dont need to tighten them that hard. Is it a bit of a overkill?

And for the last question. For those who have the same ballscrews and nuts as me ( http://62.75.219.46/shop_cfg/metall/KG-Mutter.jpg ). How much do you "preload" them? For those with ballscrews with oversize balls, how hard is it to turn the screw? How much backlash does it have?

My X axis has about 0.0015" backlash and the same with my Y axis. The Z axis has 0.007" backlash because of its weight.