Do I need to compensate for the 1/8th inch or 1/4 inch bit when creating my own project?
The short answer is yes. When taking a shape into a gcode creating program, one of the values you need to provide is the bit diameter. The program then takes the radius of the bit into account when planning the tool paths.
Your bit has a width or Kerf you need to account for the distance from edges and 1/2 the kerf to get a proper distance between edges or cut. If I’m using a 1/4 inch bit to cut. If I have a 2 inch square and I want a 1/4 inch wide cut, 1/4 inch in I need to center the bit by drawing a line in a 2D CAD 3/8 of an inch in from the edge, that is 1/4 or 2/8 + 1/8 half the width of my bit . At least this is how it was explained to me.
If you are trying to cut out a circle with a 3-inch radius, you could draw a circle with a 3-inch radius in your CAD/CAM software and then instruct the software to generate gcode using an “outside profile” cut. You provide the software the diameter of the bit and the software will perform the necessary compensation to generate a toolpath, for say a 1/4-inch bit, equal to 3.125 inch radius. (3-inch circle radius + (1/4-inch bit diameter / 2) ).
“Inside profile” cuts are used when you want to cut a hole in something. Say, you want a 3-inch radius hole. You repeat the same from above but instead of selecting an “outside profile” cut, you select the “inside profile” cut. This will produce gcode to cut a circle with a diameter equal to 2.825 inch radius (3-inch circle - (1/4-inch bit diameter/2) ).
The “follow path” cut does just that, follows the path with no offset for the diameter of the bit. You can do both above using “follow path” but you have to draw the circle to be 3.125-inch or 2.825 inch depending upon what you want to accomplish. I use “follow path” a lot when I do carvings/engravings.