New user to CNC router. Recently use a ball nose bit with the default settings on some Home Depot pre-sanded plywood. My results looked like the attached picture-
For what I was doing it worked fine - I just knocked the chatter off with some fine sandpaper. So questions are-
Was it feed speed?
Would an endmill downcut been a better option?
Just cheap plywood?
Dull bit?
Thank you in advance for your feedback.
Tim
I’m not an expert, but from my experience, that is easily fixed with a downcut. Bit sharpness, feeds/speeds, and material all affect it but in general I haven’t found any settings to be as effective for this as a downcut bit.
EDIT
If you want to continue with the same bit and just remove the edges, I find a smooth cut file to be most effective instead of sandpaper. Just make sure to file down to cut the fraying edge off rather than pulling up which can splinter the edge finish.
I havent used our ballnose bits… but that photo tells me they’re upcut. For clearing I would recommend using a conventional square upcut endmill and finishing with a downcut. If you’re set on the rounded bottom edge, I would say buy a downcut ballnose for the finishing pass.
Wood species has some affect. Baltic birch is a bit “stringy”. Oak, not so much.
Just don’t do what I did when I was still super new to CNC. I didn’t really understand how the bits worked, so I told the spindle to go the opposite direction to turn an upcut into a downcut. I almost set the wood on fire the moment it started cutting. 
Then it also dulled the hell out the bit (i.e. ruined it).
Yeah, it was an old bit I tested it on. It completely blackened the tip. I didn’t even try to cut with it after that.
So now you guys got me thinking about an entirely new general thread- “Things we have screwed up at the Makerspace and the lessons I learned.” Might actually be informative and humorous. As far as the bits go, I like the rounded edges but I am going to try a v-bit. If will almost get the rounded slope I am looking for. Thanks for the advice. While I am asking dumb questions is there a bit set some one can recommend. I know they recommended Onsrud, but I did not know if someone can recommend a set that has all the ones I would need. I can hunt around, just thought I would ask first.
Tim
That would be awesome!!! :dms:
There aren’t any sets that I’ve seen for CNC router bits. It is an extremely specialized tool that uses equally specialized tooling.
If you finish with the vbit for the chamfered edge, make sure you clear with a tool better suited for clearing: an upcut, square end mill.
I think a lot of people take for granted that we have a machine this specialized.
No dumb questions, it’s great that you/others ask them. You and we all learn something - I truly believe most of our learning at the Space comes outside of formal classes. Help, advice, mentoring offered and received is very much in line with our educational mission. I think it doesn’t get the credit it deserves not the all the folks that so willingly do it.
It’s our greatest strength and asset, IMO.
I really like this set, personally. The price is a bit hefty though. I don’t think you really need a full set of carbide bits unless you’re using the router all the time. https://www.amanatool.com/ams-cnc-52-master-cnc-router-bit-collection-52-pcs.html?ff=1&fp=10881
