How to Cut Threads on a Lathe
Turning wood or metal on a lathe is both a science and an art form. The feel that the turner has for the responsiveness of the material being turned and the delicate changes in angles and pressure when using lathe cutting tools determines success when executing fine cutting detail such as threads.
Things You'll Need
- A turning lathe with chuck and a longitudinal advance feature
- A metal or wood blank
- A 60-degree angle cutter
Instructions
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Mount the Blank
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1
Determine the threads per inch that are desired for the turning project. Engage the lathe and using a blunt cutting tool round the blank off to a cylinder form of desired widest outer diameter when the piece is finished.
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2
Align the 60-degree angle point cutter with the TPI (threads per inch) gauge holding the point straight and perpendicular to the blank mounted on the lathe. Now shift the tool point slightly to line up with with the matching 60-degree angle mark on the gauge. If the lathe has a tool holder, clamp the cutting tool into this position. Otherwise note the position that you will hold the tool with your hands.
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3
Advance the cutting tool towards the cylinder to be threaded until it just touches. As threads tend to be right handed and are milled on a lathe cutting in the threads right to left or bottom to top crank the lathe in reverse until the cutting tool clears the bottom of the cylinder.
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4
Push in the cutting point towards the cylinder approximately .0025 inch while engaging the lathe motor. Look to make sure the cutting tool is touching and cutting the cylinder. Once once pass is completed, repeat the process from the bottom and advancing the cutting point another .0025 inch and engage the lathe motor. Repeat this process until the thread reaches the desired depth.
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5
Test the thread in the accepting object to confirm its fit and smooth insertion and removal. If the threads fit too snugly, put the thread back on the lathe and cut off a few thousandths of an inch more until a proper fit is achieved.
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