Tool making and the production of components for machinery is a complex industry. There are lots of technical terms used to describe the parts of the machinery and the techniques. Here, we focus on the production of threads and how that is achieved.
What is thread turning?
Thread turning is a technique used to make screw-like grooves in cylindrical objects. It can also be used inside holes. The grooves are called threads. A machine called a lathe is usually needed. The rod (cylindrical object) is spun whilst the cutting tool moves along it and carves out the grooves.
Uses of thread turning
Thread turning can be used to produce components for many machines such as Roscamat electric tapping machines. The range of taps available for the machines is detailed here: https://www.cotswold-machinery-sales.co.uk/roscamat-tapping-machines/electric-tapping-machines/roscamat-tiger-electric-tapping-machine. They include drills and sinking tools.
Alternative thread-turning methods
According to a report in the trade journal, Machinery, the usual method of producing a thread is cutting the rod with a thread-cutting tap or die. However, some people prefer to use a cold forming or roll taping method. This is where threading is carried out with a fluteless tap. The thread is created by forming the material, rather than cutting it.
Challenges of thread cutting
Thread turning places significant demands on machines. The cutting forces are high and there is a smaller cutting nose radius. It is crucial to match the feed rate with the pitch of the thread. For example, if you are aiming for 8 threads per inch (tpi) you will need a feed rate of 8 revolutions per inch.
Depth of cut
The depth of the cut (also known as the infeed) of each pass also has importance. A little more of the cutting edge of the insert is engaged on every pass. For example, if you are producing a thread of 60 degrees with an infeed of 0.010 inches, the second pass will cut out three times as much metal as the previous one. To prevent this, the cut needs to be a little less deep on each pass.
