- 1). Set up the chuck for holding the rod while it is being threaded. Use chuck jaws that will accommodate the radius of the rod and insert them into the chuck by sliding each one into its slot. Tighten the bolts on each jaw to secure it so that it does not get loose while it is spinning at fast speeds. Line up the jaws so that they spin concentrically in the chuck.
- 2). Set up the outside diameter (O.D.) cutter and threading tool for the job. The O.D. tool will cut the rod to the desired outside diameter for the thread you need and the threading tool will then cut the material to form the thread. Each one will perform a roughing and finishing pass, so make sure the cutting tools are sharp before starting, especially on harder material such as steel.
- 3). Place the rod into the chuck and close it so that the rod is held firmly. This will prevent movement while the thread is being cut. Turn on the chuck and set it to about 1,000 rpm. Look for concentricity and make adjustments to make sure the rod is spinning concentrically. Use a mallet to tap the rod or spin it by hand after you have loosened the chuck jaws to relocate it.
- 4). Set the program for threading. Include a pass for roughing the rod to just above the final dimension and include a finish pass that will create a nice, smooth surface for threading. Add a threading pass. The CNC control will automatically set for roughing and finishing. The thread operation will take several roughing passes as well as a slower finish pass to complete the threading operation.
- 5). Set the Z axis zero point for the program, which is where the machine will start all of the cutting, and run the first part. The X axis is hardwired into the machine, so no reset is necessary. Check the thread after you have finished to make sure that it is correct. Use a thread gauge of the same type as the proposed finished thread size and rerun the program if it does not go on easily. The second pass may fix it, but if not, change the offset for the threading tool to take off a bit more per pass.
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