I tested double sided board milling with the smallest tools I have,

I tested double sided board milling with the smallest tools I have, 0.3mm drill bit, 0.3mm end mill, I used 2 registration holes 0.7mm diameter and two pins with same diameter to fix the FR4 board in place. Clearance & width of traces are both 0.3mm.
I milled top layer first, flipped the board, milled bottom layer, drilled the holes, flipped the board again and cut the dimensions, flipping the board the second time was not necessary.

The holes are a bit off by 0.1mm or less … not that bad.

That looks really good. What kind of machine are you using? 2 of your vias look good in the left side, so is it possibly a missed step or was it the registration holes?

3040 with ball screws, it’s pretty accurate, the pins fit very tightly in the registration holes in both board and base.
I just put the board back in the machine, I see it can wobble just a hair with only to pins, next test I’ll use 4 pins and see if that improves accuracy.

Your board look great and is fully workable. Awesome job.

The machine X and Y axis must be perfectly perpendicular for two-sided milling operations. It took me a while to partially dismount and fix that on my 3040, which was initially far off on X axis and a bit less off on Y axis full length.
Possibly adding an option to define X and/or Y axis skew value and recalculating gcode coordinates would help to avoid this problem.

In real world with such a small machine like 3040 it’s almost impossible to get 100% perpendicular axis.

That looks really great. Looking forward making a few double sided boards some time. Are the vias 0.3mm? Are you using a V bit or end mill for the traces

Yes, vias are 0.3mm, I’m milling traces with end mill, much better than V bit.
BTW, I fixed the issue you raised earlier, I made a pull request few minutes ago.

Great thanks a lot for that. I will give it a go later on. Was also wondering as i am still just starting what are the settings you use for the net class in eagle ( thace thicknes and clerance). From your image above thay look quite small.

I try to match my designs with the tools I have, for this board I set clearance to 0.3mm which is the diameter of my end mill, in this case inflate value in the widget should be set to 0.15mm.
Trace width of this board is also 0.3mm.
If I want wider clearance, I mill traces twice with different inflate value.

What are you going to do with the vias? Solder a strand of wire through?

@ameen.nihad Thats realy great, i’m curios if it possible to send us a Picture with the complete board and they registration holes?

@Frank_Herrmann here is the complete board, I only used the top and bottom holes in my test, next time I’ll try the 4 holes.
missing/deleted image from Google+

I did this around 6 months ago (before my house fire) and my registration holes were the same style but I failed (miserably) to attain alignment for the rear paths.
Please do a picture guide for this (even if it is rough) because it would be wonderful

@Ritchie_Wilson 6 months ago Eagle BRD widget was missing the functionality to mirror board layers, I wonder how did you mange to mirror the back side? I will do another test next week, I’ll try to document the steps.

It was at least before 31st August (exact date of my house fire) I attempted two sided. I clicked the checkbox and it did cut into the board but massively out of alignment. Maybe it did the top cut but I was so angry I’d screwed up i didn’t notice.
Documentation would be amazing