A metalworking lathe, like a woodworking lathe, is a device that is used to shape and mold metal to unusual shapes that are not possible when working by hand or with basic tools. Many people find a variety of uses for a lathe in their home studio or garage. One of these uses is to create threads in a screw or a portion of a metal object. By threading an object, you help to provide security for that object when it is put to use. Threads help to hold a piece of metal in place, and give it stability. Read on for a brief guide on how to cut threads on a piece of metal with a metalworking lathe at home.
Step 1 -- Prepare the Metal
Begin by considering how many threads you'll need on the metal piece per inch. This will determine how the piece can fit into the item that you'll be inserting it into. If you're working with a solid piece of metal, begin by turning on the lathe, and using a blunt cutting edge to trim down the piece of metal, so that it's the appropriate size and shape. You should have a cylindrical piece of metal that has a diameter as wide as what you'd like the widest point of the final product to be.
Step 2 -- Set Up the Cutter
Set up the 60 degree angle cutter, aligned with the threads per inch (or TPI) gauge on the lathe. It should be straight and perpendicular to the metal piece. Shift the tool point on the lathe, to match up with the line of the 60 degree angle cutter. Clamp the cutting tool in place in this position, if the lathe has such a clamp to do so.
Step 3 -- Cut the Threads
Push the cutting tool in toward the metal piece, until it just barely touches it. Crank the lathe in reverse as you do so, and cut from the bottom of the metal piece up to the top, in order to ensure that the threads will be oriented in the right direction. If you get this backwards, you'll have to turn the metal piece in the opposite direction in order to tighten it in place.
Step 4 -- Work Slowly and Carefully
Check to make sure that the cutting device has reached the desired depth for the metal thread. When it has, remove the cutting device and move it carefully up the metal piece, so that it will be in the appropriate location for the next thread. Cut into the next thread gently, and be sure that you don't cut any deeper or shallower than the first thread. Continue up the metal piece. Be sure to test out the threads after you're done, to ensure that they are the appropriate size.