ROUGHING BITS

A roughing bit clears the bulk of the material on a deep carve before a finishing pass adds the detail. Its job is fast material removal rather than a clean surface, which cuts down the total time your machine spends running. Roughing bits earn their place on 3D carving, deep relief work, and any CNC woodworking project that starts from a thick piece of stock.

The roughing pass goes first and clears waste material quickly, leaving a rough surface behind. The finishing pass follows as the finishing tool for the job, cutting the final dimensions and the fine detail, often with a ball nose bit for a smooth surface finish on 3D work. Running both is faster than making a single bit do the whole job and gives you a cleaner finished product. 

Match the shank to the collet in your machine. Compact routers usually take a 1/8" shank, most desktop machines take 1/4", and large or industrial routers take 3/8" or 1/2". A bit with more flute length reaches deeper in a single pass, but reaching for the largest size only helps if your machine has the power and rigidity to drive it.

You set up a roughing cut in your CAM software, the program that turns your design into cutting instructions. Choose a roughing or pocketing toolpath, select your roughing endmill bit, and set a stepdown that leaves a little material behind for the finish pass. The software exports a gcode file that your machine reads to run the cuts. Vectric, Carbide Create, Fusion 360, and Carveco all handle this, and our database downloads load the bit settings straight into Vectric. 

Start with the numbers we publish for each bit, then adjust for your material and your machine. Our chipload calculator gives you a starting point based on bit diameter, spindle speed, and feed rate. Solid carbide holds its edge at high speed and has the heat resistance to handle harder or more abrasive stock, though you should slow your feed rate on those materials so the cutting edge does not overheat. Running the right feeds and speeds does more for tool life than anything else you can control.