Quick guide for milling tools
Since I "only" have access to use 3,175mm bits (1/8 ") both due to my choice of a mini CNC cutter, whose flimsy can not hold on to metal for quite a long time. There are many topics about tools that are actually not relevant when we are talking small sizes. End mills are made of, typically carbide or HSS, although there are a few more exotic alternatives such as powder metal. It depends on the material to be cut, as well as on the maximum spindle speed of the machine. If you are not able to reach the recommended speeds, you may well discover HSS end mills make more sense.
The number of inserts depends on the material you want to cut and the options in your machine. Most often it is about having as many inserts as possible as they act as a "spindle multiplier". For a given spindle speed and chip flow, a 4 insert can be fed twice as fast as a 2 insert. The most common options are 2, 3 or 4 inserts.
Depending on which way the spiral goes on a cutter, you get a cutter that either moves shavings up or down. Then an upcut will move the chips up and out of the cut and it will tend to pull up on the workpiece. An upcut is a conventional end mill for all purposes. For wood and materials that can shavings have the disadvantage that they pull shavings along the top edge. A downcut pushes down, leaving a cleaner cut at the top, but can fray the bottom edge. It is an advantage to have the material diverted away. And keep it, tempered. Wood burns black, Plastic melts, metal becomes tarnished.
They look like a wooden rasp. They are good for finishing cuts, but their ability to remove shavings is limited. Since they are gentle on the material, they are often used with composites, PC sheet material, and other layered materials.
Straight Flute Cutters
On a helical insert, cut it all at once as the entire edge slams into the workpiece. It does not work for metal. Although a grooved cutter goes 3x faster, leaving a better finish, they are inexpensive and come with different profiles.
Commonly used for engraving: The simple geometry of the knives prevents them from being useful for quite a lot, but they do a good job of engraving and give nice clear pictures, letters and numbers.
There is not much to say about drills, the small dimensions break easily if pressed lightly, from the X and Y axis, whereas for ordinary holes (Z axis) they are phenomenal, for example in a printed circuit board when drilling out for components.