I’m getting tooled up for a huge entry door project and I need a bit that will produce a very clean edge cut. I typically make cabinets using a 1/4” compression bit and it leaves a small raised line at the point where the two directions meet. I’m guessing a 3/8 bit of some configuration would be best but I’m not sure which. Any suggestions that would help me get a clean, sharp edge?
that's typical of a Cnc machine. if the bit is long enough to cut in a single pass then use climb cuts and the last pass a full depth regular direction cut. thats the best way to get accuracy and eliminate tool marks. if it is a deeper cut then the 1" or so that the 1/4" then use a bigger bit.
What thickness lumber are you cutting?
Similar concerns compelled me to try 3/8 and 1/2" bits for the thicker lumber I assume you must be cutting, considering entry doors.
If you're in the 5/4 - 7/4 range, ditch the 1/4", ditch the compression configuration. I've found 3/8" for hardwoods of this scale to be best. Getting rid of the compression bit gets rid of that transition line. I'd use a 3/8" up-spiral with cut length that slightly exceeds material thickness. 1/2" is an excessive kerf for cutouts, but for light edge dressing (tenon cutting) it's divine.
Chip breaker bits are worth noting - they'll rough out a cut with less splintering, but introduce multiple transition lines, due to the "siped" cutting edge. You would need to then switch to a clean standard upcut for that final cleanup pass, but you've now introduced another tool change...
At the end of the day, sanding is inevitable if perfection is the goal. Proper bit selection will simply reduce duration and intensity of sanding process.
I'll be cutting 12/4 Sapele for this job. I had not thought about using a climb cut, but I did figure I needed at least a 3/8 bit for the main cutting operation. My main concern is that I will need to machine 8 delicate arches, 9" X 4 1/2" half circles actually, moldings with a 45 degree miter on each end for the Glass panels. I would post a drawing but I've never been able to figure exactly how to do that on this forum, lol. Basically, it's a rectangle with a half circle at the top, but the half circle does not extend to the edge of the rectangle. The parts I would like to machine will be the ones that hold the glass in at the top, a piece of widow stop essentially. My experience tells me that there's no way to do that without blowing out the tiny tips of the miter. Do y'all know of a way to do that? Is there a particular tool path strategy that would make those cuts without blowing them out?