Step 9: Z-Axis Lead Screw and X-Axis Aluminum Angles
This tutorial is dated, if you are considering a CNC for your personal use, we would highly recommend purchasing a kit that is very stable from our wide range of machines available. Instead of using allthread for the lead screw and a standard nut, consider using a 5 start lead screw and anti-backlash nut. It will keep you from pulling out your hair by running much smoother and faster. Lead screws... hmmm... ok, let's talk concepts. The lead screw is the main component for the transmission of power in a linear form. Yes, a little like the transmission in the car, but much simpler. The screw yields a ratio of force to the linear motion, but conversely affects the speed and resolution of linear motion. To explain in more simpler terms, take a regular screw, and a nut. Hold the nut in one hand but don't turn it. Hold the screw in the other hand and screw it in the nut. Your hand is applying a force to the screw in a circular motion, hence the motor turning the shaft, and if the screw is turning at a stationary point in space, it will pull the nut toward the hand turning the screw. If the turning motion of the screw is reversed, the nut is pushed away from the hand turning the screw.

Step 2 - The Cheapo Connection
Check here for our cross dowel nuts that are used in this tutorial. These are a great way to create joints in wood. If you are looking for some great CNC machine kits, look here. Making corners, connecting two pieces of MDF can be a challenge. I am going to run through a technique, and a vital element in the CNC machine of this tutorial. This step is not as glorious as building an actual working component of one of the CNC axes; however, this type of connection is used on almost every part of the machine. The idea is very simple: with two large holes to receive nuts, and two transversal holes to receive screws (long enough to reach the nuts), a tight and strong connection can be achieved. Not only is this connection strong, it also helps to create the tension desired to tighten an axis assembly around the rods/angles for snug no-play sliding. Other types of connections that I have tried are weak and prone to splitting. I have had no splitting or failures with this method.

John S.C.'s CNC Machine and Suggestions
John S.C. did something that I have not yet seen. He applied a ball-screw to the DIY version of the CNC Machine found on the step by step and the book "Build Your Own CNC Machine". Yes, you heard me right! A ball-screw. Why do I sound excited? Read on.