There was some discussion earlier about just what caused my machine to cut wide. So I reseated the tool in my router, and did a test cut on a piece of scrap. Here it is compared to my first cut. Like I said, the bit was set in the collet poorly.
I was in such a hurry I didn’t even cut the reversed pattern. But you should get the idea.
This also means you are using a tapered bit though. Why? I have end mills of 0.2mm that route PCBs beautifully regardless of cut depth.
As I am a Chilipeppr user my biggest issue is flipping the board and getting the position current again. Of course this is user error but I’ve wasted a lot of FR4 in bad placement.
@Ritchie_Wilson
I use a tapered bit because it is robust. Although like you say setting the depth is a bit touchy. I use a rolling paper. That gets me within a thousandth. As far as your board placing woes go FlatCAM supports alignment pins. So you might want to give that a shot?
@Paul_Frederick Thanks i shall have a butchers. http://cutwel.co.uk is where i get my bits and they are technically for aluminium so PCBs like butter 
the only issue then is the FR4 being flat but I use Autolevel to cope with that.
