PCB milling with V tips - which one works best for fine tracks

[suspension]

Hi all,

I have tried milling a PCB (smallest track/space around 0.2mm) with 0.2mm, V shape, 30 degree bit but results are extremely poor. The copper seem to melt (even if I setup coolant during milling), edges are rough and finer tracks are narrower than the design. I have tried this with different feed rates, different depths, different bits, but results are same.

Then I switched to 0.1mm, 10 degree, V shaped bits and results are amazing in the first run it self. Only issue with this is they break easily. On top of that I have run out of such bits now and will have to wait for 3 weeks to get new ones from aliexpress. (This is not available locally). But I seriously want to finish a PCB which I started to work on soon.

My question is, does any one here had any luck using 0.2mm, 30degree, V shape bits to mill a pcb which has 0.2mm tracks nicely? I am talking about the quality similar to what you see in all wegster CNC channel in you tube. With 0.1mm, 10 degree V shape bits, the quality was similar.

Cheers

[IconicPCB]

I have no problems with 0.0071" tools.
In fact the smallest tool I use is 0.004" under protest.
Yes they are a bit more sensitive than the 0.010" tool but such is life.
What spindle speed, linear feed rate, Z axis depth control do you work with?
What is the run out of Your spindle?

[thm_w]

I don't think you want coolant, you want a vacuum to get rid of that nasty dust.
But yeah, same question as iconic, what is the RPM.

[IconicPCB]

There is a coolant product out there specifically formulated for copper on FR4 but then who wants to see that on a freshly milled board?

And Yes a lot goes into machining... much more than some who got stung by a well known brand thought when going into this game.

[MR]

I have milled quite a few PCBs so far and never had any issues once I figured out how it works (so my only reason for breaking those small endmills was lack of knowledge or inappropriate handling of those tools)

I'm using various TMD endmills (from Taiwan Microdrill Ltd.) and I'm absolutely satisfied with them.

[PlainName]

I think your mistake is to go for a narrow angle on the basis that the track width won't be affected much by depth of cut. I did that a lot and wound up with pukka LPKF 100890 PCB bits which have a 60 degree angle (also got 90 degree ones). They are €180 direct from LPKF  but I picked them up for a LOT less on Ebay. The bigger angle makes them more robust and less prone to wander. Or breaking.

The trick is to have perfectly flat boards. Many setups have a system for detecting surface imperfections and making allowances for them, but I found just using carpet tape to stick the things down was good enough.

Dry cutting will lead to poor copper edges. Not immediately, but once the tool starts to go blunt it will. So the trick there is to just put a film of 3in1 or similar oil across the board as lubricant. Doesn't need flowing coolant, just a mm or so across the board.