Gerry to note, I snapped a 3/8" bit, which was carbide body with PCD tips!
There are a few thoughts on this. It really depends on what you're doing.
For harder materials, pocketing may be the way to go. Especially if it's a long run with many holes. You might think that you're wearing the bit more but it may not be necessarily true. If you pocket and use a large enough bit, you can take deeper cuts, even through cuts, and take more aggressive rough cuts. You'll generate less heat since you're cuting more on the edge of the tool which is way more efficient than the bottom. The finish pass would then be the full depth profile. You'll actually get better tolerances this way, and it's the way they do it in metals. Some CAM (even Cut2D) have rest machining for pocket clearance as well. If you profile cut the holes, you'd normally have lower doc since you have full width bit engagement. You're climb cutting on one side and conventional on the other, so the bit wants to move toward the conventional side. If your machine is not super-ridgid, you'll have tolerance issues. I understand m machine is not the stiffest, therefore to achieve a certain tolerance, I run finish pass on 'mission critical' features.
For larger holes, it may be beneficial to do a drill op on the center of the holes and fix the soon-to-be slugs down with screws, before cutting the profiles out. Another way would be to onion skin with a larger bit, then come back with a smaller bit to profile cut the rest out. The smaller bit won't grab as much, and the onion skin will prevent the slug form binding the bit. Yet another way, and probably only worthwile if you had to do a large run, or have many holes, is either to raise the workpiece, or create a fixture with pockets or holes, this way the slugs fall down and out of the way. Yet another way would be to tack the slugs down with a 23ga pinner.
I had to cut out some letters out of thin gauge (1/16") brass sheet. The best way I found was to glue the sheet down with CA glue, let it cure, profile cut the letters, then remove them with acetone. I tried spray adhesive but there is always a little 'creep' and the glue gums up the bits. Plus if you spray a tiny bit of lubricant it will work under the letters and pop them out and ruin them. I got the tip from Ron Reed at precisebits.com.
But yes, when cutting out holes, you'll have to assess the situation and consider the tools you need when deciding whether to pocket or profile.
You might want to use tabs on a 3D relief, like an ornamental, where there are intricate details that may get lost or not be as crisp by sanding the onion skin off.
I did that the other day it don't happen to often but it was cool I lifted it right out all that stayed was the film..
Louie I am subscribed to your you tube channel I really enjoy the videos what did you use to carve the aluminum Harley Davidson logo? Some great work I was showing my wife and Daughter they really like the videos as well.
I really like this Amana spoilboard cutter. The inserts are 2 bucks a piece and they have 4 edges.
My main machine: Multicam MG series (MG101) with original Extratech H971 controller, Minarik servo motors, Electro-Craft BRU-series drives, 4KW Colombo. Let's talk Multicam!
Louie thanks for the information I forgot to ask you what spindle speed and feed rate?
My wife and Daughter have a embroidery machine and are in to basically the same thing but the use fabric so this is up there alley