Taig Lathe Threading Attachment

thingiverse

Demo video: https://youtu.be/VILK6h7MCjQ I wanted to cut threads on my Taig lathe without using a tap and die. I have seen different attachments that people have devised for thread cutting. I wanted to make one that doesn’t require any modifications to the lathe components and be relatively simple to install and remove. I also wanted the hardware components to be something that you can easily find at a hardware store. This unit is not designed to be a power feed. As is, it is designed to be turned by hand. The spindle gear is a friction fit onto the headstock pulley. I have added holes to it for set screws, but so far I have found that the friction fitment holds it solidly enough. The bushings in the lead screw carrier are 3/8”x1/4”. You will need 2 of those. The nuts used are ¼-20. The threaded rod used is ¼-20. The washers are ¼”. The lock collar is ¼”. The gears have a 14.5 degree pressure angle. The spindle gear, gear A, gear B, and the leadscrew drive are the gears that determine the screw pitch being cut. The other two gears are simply idler gears. I haven’t tried cutting left handed threads but you should be able to do so by adding another idler gear or removing one. I have found that the 80 tooth gear works best for driving the leadscrew. I have used smaller ones but it tends to skip teeth. I guess it is more difficult to transfer the 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 do not change the TPI. They only transfer force. It would probably be easy to make an M6 leadscrew for cutting metric threads. I haven’t tried that yet. Or you could just print the correct tooth gears to cut metric threads using a ¼-20 leadscrew. The parts were designed using Fusion360 and FreeCAD. I found that making gears is a lot easier in FreeCAD using a gear plugin. The gears have a 12mm bore. You will need to print 2 of the 80 tooth gears. You will need to print 2 of the GearBushing.stl. You will need to print 1 of the StackedGearBushing.stl. I currently working on an indexing attachment so that you can make multi-lead threads. I may also work on creating a handwheel to use when turning the spindle.