Taig Lathe Threading Attachment

thingiverse

Demo video: https://youtu.be/VILK6h7MCjQ I set out to create a thread cutting attachment for my Taig lathe without using a tap and die, which I had seen others accomplish with various attachments. My goal was to design one that wouldn't require any modifications to the lathe's components and would be relatively simple to install and remove. Additionally, I wanted the hardware components to be easily accessible at a typical hardware store. This unit is not intended as a power feed; it's designed for manual operation. The spindle gear fits securely onto the headstock pulley via friction, with holes added for set screws, but so far, the friction fit has proven sufficient. The bushings in the lead screw carrier measure 3/8" x 1/4", requiring two of them. You'll also need: * ¼-20 nuts * ¼-20 threaded rod * ¼" washers * ¼" lock collars The gears feature a 14.5-degree pressure angle, with the spindle gear, gear A, gear B, and leadscrew drive determining the screw pitch being cut. The remaining two gears are idlers. To cut left-handed threads, you can add an idler gear or remove one. I haven't tried this myself but believe it should be possible. For driving the leadscrew, an 80-tooth gear works best; smaller ones tend to skip teeth due to difficulty transferring force through the system. The formula for determining the TPI to cut is: TPI to be cut = Leadscrew TPI / (Spindle Gear/Gear A)*(Gear B/Leadscrew Gear) Example: 16TPI = 20TPI LS / (80/32) X (40/80) The idler gears don't affect the TPI; they only transfer force. It's likely easy to create an M6 leadscrew for cutting metric threads, but I haven't tried it yet. Alternatively, you could print the correct tooth gears using a ¼-20 leadscrew for metric threads. I designed the parts using Fusion360 and FreeCAD, finding gear creation much easier in FreeCAD with its gear plugin. The gears have a 12mm bore. You'll need to print: * Two 80-tooth gears * Two GearBushing.stl * One StackedGearBushing.stl I'm currently working on an indexing attachment for making multi-lead threads, as well as a handwheel for manual spindle operation.