Hi Mahmood,

I thought I remembered posting a picture of one of my old prototypes. In particular, I posted a photo showing the CP2102 land pattern I milled. As I said, it's the smallest one I can do reliably with my standard tool. Here's a link to the old post.

http://www.8052.com/forum/read/162836

My first suggestion, to learn the limits of your machine, would be to do some tests to measure the precision and repeatability of your machine. If you send the bit to coordinates (x, y), how close to (x, y) do you actually get? How repeatable is your machine? Knowing this will let you know how fine a feature you can expect to machine. If you're milling a 0.004" trace, but when you go back to that coordinate your machine is off by 0.004", your trace gets obliterated.

Another problem might be, as Per pointed out, dull bits. If your bit isn't cutting efficiently enough for your feed rate you could be just pushing fine traces out of place. Of course, one you do that there's nothing holding the trace in place and the bit will chew it right up.

But in any case, the first thing you need to know is how precise and repeatable is your machine.

Good luck,

Joe