Hope I’m allowed 2 question in one day. 
In Eagle BRD Import, it appears it only allows a single operation for all the isolation routes. i.e. 1 cut. But sometimes I’m left with sort of hanging chads. Bits of copper that get missed but are too thin to really stay stuck. This results in having to go back and tediously scrape them out with a blade. Is it possible to have a second route to widen the gap a bit? Not sure if I’m just doing it wrong or making a feature request.
Thanks!
For what it’s worth, I use an LPKF board milling machine at work, with a completely different software flow, and it does the same thing, even if I set it to double-mill.
This is why you can play with inflate/deflate of paths to try to eliminate stuff like that. There’s a checkbox you can do to see a light blue path cut to see where you may have areas you don’t like. You could inflate your path to remove hanging chads. Typically though I deflate paths because I want the thinnest traces I can get. You can also individually inflate/deflate traces vs pads vs vias so play with advanced settings, which I think is super unique and haven’t seen elsewhere.
Thanks for the tips. I was playing with inflation earlier and although I really like the ability to adjust the size of my traces post-Eagle, my isolation routes will always be the width of my v-bit based on depth. I could go deeper but I don’t want the grand canyon. heh. I just went back to playing with PCB-GCODE ULP for Eagle and managed to get a rather sweet board from it. I just really loved the idea of using ChiliPeppr as a one stop shop for my flow. It’s just that PCB-GCODE is old and the options to cut out the finished board are terrible. So I just used Eagle BRD Import to open my BRD file and skipped ahead in the Gcode to the part where it cuts out the board and used it to do just that part. LOL. What a messed up flow I have now. Maybe we can have an option in Eagle BRD Import to generate Gcode only for board cutout or only drilling or only traces?
Inflating/deflating traces does not matter what bit / end mill you use. It’s simply a matter of making traces wider or narrower, not deeper. I have found best results from PreciseBits.com rather than v-bits because v-bits require you to sand afterwards and they’re not ideal. http://www.precisebits.com/products/carbidebits/tapered_stub_125.asp is the way to go for real accuracy although you also need ballscrews rather than timing belts to get real accuracy.
Great recommendation. I’ve visited http://precisebits.com before of course but never purchased anything because honestly it made my head spin and when you consider how expensive they are, I was afraid to pull the trigger for fear I’d spend 50 bucks on the wrong thing. V bits are really cheap and seemed popular for PCB milling. But I think I’ll order a 0.254mm or something along those lines from them and see if that helps clean things up when using Eagle BRD Import. Thanks.
As far as accuracy, my rig is a Shapeoko 2 with belts. Maybe some day I’ll build a mill with ballscrews, but for now I’ll make do. 
I have this thing rather well tuned mechanically I feel.
If you want a great finish for delicate PCBs you need two things:
- Run Autolevel
- Decent end mill bit (0.2mm is readily available)
I use a company called cutwel (http://www.cutwel.co.uk) I’ve bought most of the surviving kit for my CNC from them so its good stuff. It is however for “proper” CNC so made to high standards and can be a bit pricey.
I’ve broken many things from other suppliers hoping for it not be a false economy and am yet to be rewarded 
I am currently attempting to get double sided PCBs to be viable on my machine but have had alignment issues after the flip. I won’t jack your post with my woes though
Years back, I was very active in the Test Engineering/In-circuit area. We built large oin count bed-of-nails tests for probing circuit boards. We used pins at that time from 0.1" to 0.05". We probed top and bottom, using tooling pins in the diagonal corners of the PWA’s. I would think adding tooling pins on the corners would allow an easy flip for the second side to align very well. I have seen videos where guys are taping the boards down and just do not see that working for anything with fine pitch traces and small vias or large PCA panels. Our tooling pins were generally 0.25 - 0.125" drill stock. Some times, we woulds grind them to a “D” profile or a triangle, to make it easier to mount/dismount the boards in the test fixtures. BTW, this is a great way to make a test rig to test multiple boards if you need to. Adding spring probes to a base with tooling pins and a clamp is a good way. We used vacuum to pull the board down onto the probes.
i drop my cnc’d pcbs in some ferric chloride for a few minutes after milling, it cleans up the edges and these burrs