February 12, 2008
So, what does a woodpecker do? It pecks, and the pecking is to bore a hole. It would be very difficult for a woodpecker to bore a hole in a tree with just one thrust into the tree. The same goes with machining various materials. I previously mentioned pecking in a previous page, but I think it's important to mention it with an example.
In the video, you will see the CNC machine in action, using a method called pecking. Simply, pecking is the process of inserting the bit into the material and pulling out to release the material from the bit. At high bit speeds, this is especially important. The chips of the material being cut will lodge into the bit and expand. I have had bit completely break off during my early learning of machining. Even with pecking, you will still notice the odd "pop" from the material being released at high velocities. In fact, if you watch closely, you will see this happen in the video. Another result of not pecking will slowly move the bit out of the collet. The material will build up in the bit, expanding the material until the upcut bit will force itself down into the bore. Upcut bit is a bit that forces the chips in the upwards direction. This is done by the direction that the flutes of the bit are arranged.