When you use a die to cut threads on a rod, the rod has to be more slightly smaller than the nominal size of the threads that you want to create. The nominal size of the threads is just a name for the measurement of the threads. However, the nominal size isnt always the same than the measurement that is required for cutting the threads with a die.
For instance, if you take a quarter inch rod and use it to cut quarter-inch threads with a die, you will find that the rod is too large for the die. Dies work by shearing the metal rod to form the threads. However, if the rod that you use has the same measurement as the threads that you want to create, there is too much metal for the die to be able to cut.
How to Use a Die to Cut Threads
As a result, the die will jam within the rod. Additionally, the die may crack within the metal rod, or the threads may strip as the die forcefully attempt to cut the metal. For these reasons, it is necessary for the rod that is used to have a smaller diameter than the threads that are to be created.
The amount of undersizing that you must perform on the metal rod is related to the diameter of the rod. Additionally, the amount of undersizing is also related to the type of threads that you are creating. For example, if you increase the diameter of the rod, then the amount of metal that must be removed to allow for the dies to effectively cut the threads increase as well.
This is because rods of increased diameters will produce more metal chips than rods with smaller diameters. If you dont properly remove the metal chips created during the cutting of the metal rod with the dies, then those metal chips will begin to clog the dies. As a result, the dies will not be able to properly cut the threads on the metal rod.
The type of metal from which the rods are made will also impact how the dies create the threads on the rods. Metals like mild steel tend to work well with dies when using standard cutting oil. Metals like stainless steel will work harden when rubbed against the dies without cutting the metal.
To cut stainless steel with dies, it is important to slowly cut the metal, as well as use a sulfur based lubricant. Finally, metals like aluminum are soft metals that will produce gummy chips when cut by dies. These gummy metal chips will quickly clog the dies.
For this reason, metal rod made of aluminum will require that you regularly remove the chips from the dies. Before cutting the metal rod with the dies, it is necessary to prepare the end of the rod. It is not necessary to place a raw piece of metal rod into a die to cut its threads.
It is necessary to file a 45-degree chamfer on the end of the rod. If you do not file a 45-degree chamfer on the end of the metal rod prior to cutting with a die, the die may catch on the end of the metal rod. As a result, the die may begin the threads on the rod at an angle.
Angled threads cannot be corrected once the dies have begun the cutting process of the metal rod. When cutting the threads with the dies, it is necessary to turn the dies forward one full rotation, followed by one half turn backward. By turning the dies backward one half-turn, the metal chips created during the cutting process are broken into smaller pieces.
These smaller metal chips will clear the flutes of the dies. By using this method to turn the dies, the person using the dies will cut more metal with less effort. Additionally, it is recommended that if the dies are adjustable, the two-pass system can be used to cut the threads.
The two-pass system involves leaving the dies slightly open to make the first pass in cutting the threads in the metal rod, followed by the final pass through tightening the dies. Prior to beginning to cut the threads in the metal rod, it is important to ensure that the diameter of the rod is the correct size. You can use a micrometer to verify the diameter of the rod.
By using a micrometer to measure the rod, you ensure that the rod is not oversized with respect to the threads that are to be created. Furthermore, if the rods are of the correct undersized diameter, have a clean chamfer filed into their end, and if they are turned with the proper rhythm, the dies will create clean threads in the rods. The quality of the threads will depend upon the fact that the rod is of a slightly smaller diameter than the threads that are to be created.
