I could see where theoretically the 4 edge could be better with chip clearing, for me being only a one man shop with a 3HP dust collector on my CNC machine that I rarely run faster than 300 ipm(usually never faster than 175 ipm) I find the collector clears the chips faster then the bit can produce chips at the rate I cut anyhow.I would assume there is some issue with chick clearance? or maybe the ones with multiple cutters are easier to sharpen?
That works, but for a CNC Spoil board I do not recommend using that type bit for the sole purpose of stopping ridges.. Those bits cut flat, they don't leave ridges. It is not the bits that cause those ridges and if they did who would buy them and what purpose would they serve. I suspect as long as the bit is not defecteive for the msot part the ridges come from jigs, fixtures or CNC machine that are not set up perfectly, trammed or otherwise. Or from a the routers themselves that simply do not have balanced enough collets or have slop in the plunge mechanism or jig or fixture mechanism, I am talking very small tolerances. The wider the bit the tighter the tolerances need be.For planing I prefer to use a dish cutter as it's more tolerant to slight tilt of the router, whereas bottom cleaning bits that I used to use can cause lines where the corner digs in.
For hand use, yes. For CNC, no. If you're not able to use a flat bottom bit because it leaves ridges then going to a bit that doesn't produce ridges just hides a poor setup on the CNC; you haven't 'fixed' anything but have simply masked the problem. That needs to be corrected such that you can successfully use a flat bit or a rounded dish cutting bit.in my opinion the dish cutter is more tolerant.
Mine did last for 2 and a half years, and I had to replace it with a new one. Use spiral compression router bits to cut the plywood cleanly on both edges without pulling it out. The sharpness of the upcut and downcut flutes of compression router bits. As a result, the flutes compress the plywood as they cut it in both directions. The only thing that I don't like to do, is to clean after I do the work. You need some special solutions to clean that dirt, therefore I prefer calling a professional service from Commercial Cleaning Services in Portland, Oregon — Cleansolution, to clean it for me.I've been using my flat bottom bit for the past 4 years to surface the spoilboard and occasionally flatten a rough piece. It's still cutting plenty good 'nuff for me.