Hi! I’ve a home made CNC and it uses a dremel as a splindle.
I want to route pcbs on my CNC and I was thinking what kind of bit should I get for that job.
I’ve used a 60° V shaped bit for that job before, but I don’t have any of those.
What do you recomend?
Thanks!
I saw a guy use a tiny end mill and it looked like it worked great to me. I used a 20 degree V bit, and it was so so. Very sensitive as far as depth went. The end mill demo I saw looked like it was better to me. I didn’t even know those tiny end mills existed. I think it was one thirty second of an inch? It was small.
I’ve used a small glass cutting bit before. They give good results, are inexpensive and you can buy them locally in almost any hardware store. And they’re carbide!
Tangentially. Watch your run-out on your dremel. The bearings in those aren’t meant to deal with repeated side loads.
I have seen bits that just amount to a pointed shaft with half of it milled away to make for a single flute 30 degree? bit.
@Citrus_CNC
You mean a diamond coated bit? I’d think they would load up.
No matter what you use the fiberglass will chew up your bits.
@Paul_Frederick
Something like this http://www.homedepot.com/p/Bosch-Glass-and-Tile-Drill-Bit-Set-4-Piece-GT2000/202242753
They have a brazed carbide insert, and come in various shank sizes.
Thanks!
@Citrus_CNC
Ah OK thanks. I thought you might have meant something like these https://www.walmart.com/ip/Rotary-Tools-Diamond-Grinding-Bits-Set-20-In-1-w-Organizer-Case/105532789?wmlspartner=wlpa&selectedSellerId=571&adid=22222222227044267050&wl0&wl1=g&wl2=c&wl3=108201558917&wl4=pla-302653004957&wl5=9007515&wl6&wl7&wl8&wl9=pla&wl10=111838760&wl11=online&wl12=105532789&wl13&veh=sem
I do not know what bit to use, but I have advise for when you do not use it for PCB. When cutting anything else with a dremel, be carefull to keep your cut depth shallow or you will have your dremel tool’s shaft bend.
Be careful to make sure that your dremel tool’s shaft is perpendicular to the work area in both X and Y dimensions or you might have odd results.
@Citrus_CNC those bits are pretty nice. Thanks for posting.
@Chaotic_Logic
Glad you found the post useful! 
60° bit is probably good for starting. You can play with my Calculator (http://woodworkerb.com/home/pcb-isolation-routing/tool-width-calculator/) to see that even minor changes in depth have a pretty substantial impact on the width of the cut. Leveling your board as precisely as possible is it good starting point. Depending on the complexity of your board: an auto leveling routine would probably be indicated.
Also, I’ve been very pleased with bits from this company: http://www.precisebits.com/applications/m/pcbtools.htm
@HobbyCNC thanks!
60 deg V bit. Very shallow cuts and a auto leveller program
http://www.autoleveller.co.uk/.
More info here. http://woodworkerb.com/home/pcb-isolation-routing/tool-width-calculator/
Use the stub end mills from http://precisebits.com and then use ChiliPeppr to drag in your eagle board, auto level, then mill.
In a pinch I used a bit that had a small ball end that I have gotten in every Dremel bit kit I’ve ever gotten. I used it just because I had a few of them kicking around but it worked fairly well. I only made two simple boards with it before I switched back to photo resist/etching so I can’t comment on the longevity.
@Andrew_Rousseau
Those Dremel bits are made for working with balsa wood. So I doubt one would hold up cutting fiberglass boards for very long.
I wonder if those glass cutting bits will last longer in the FR4… it’s FiberGLASS after all. Wondering why I never thought of trying that. Thanks for the suggestion.