A metal lathe can't really be called complete if it cannot cut threads. Cutting threads requires that the carriage and thread cutting tool move at many different rates in relation to the turning spindle. Traditionally this is done by changing gears in a train of gears. Below is a very old picture that shows the number of gears that might be needed. Today, any one of these change gears would cost more than our entire lathe should cost.
change_gears.jpg Change gears are not practical a for a large,low cost lathe but there is a another choice, a device called a thread follower. Thread followers use an existing sample of a thread and "follow" it to move the carriage at the proper speed. Followers are used to cut very accurate threads used in watch maker's tools and scientific instruments. Our follower was inspired by this 101 year old Scientific American article and uses blocks of hardwood to "follow" the existing thread and thus allows the threading tool to cut a duplicate. Our new thread may even be more accurate since the blocks of wood might average out imperfections in the sampled original thread.


A bit obsolete but the idea of following the thread with pieces of wood is wonderful because it would let us use a thread follower threading device without having to have a nut of the correct thread that would be used to "follow" the sample thread. The "follower" is driven from the rear of the spindle by 2 bike sprockets with the same number of teeth. The shaft of the follower fits into a cartri