SHEET METAL THREAD
Sheet metal thread. The thread is a special mechanical working that can be performed on a cylinder (screw) or on a hole (female thread) and it consists in creating a groove with a helical shape to allow the mechanical coupling of two bodies. In order for the union to be possible it is necessary that both bodies have the same thread characteristics.
Practical and economic reasons have prompted international governmental bodies to issue norms on thread world standardization. Despite this, nowadays many types coexist:
1) The ISO metric screw thread – international standard recognized since 1947: it consists in a type of thread with triangular profile with an angle of 60° – non-sealing.
2) The Withworth screw thread – similar to the ISO metric screw thread, but with an angle of 55°: it plans mechanical contact between the two bodies both on the sides of the threads and on the edges – which instead is sealing.
3) The unified thread (in inches) with smoothed edge and connected bottom.
4) The BA screw thread with triangular edge and connected bottom to large radiuses – walls at 47°30’
5) The American Standard screw thread with bevelled edge and bottom – walls at 60°
OUR WORKING OF SHEET METAL THREAD
Our working. The thread working can be realized through many procedures. The most common are:
– by fusion;
– by pressing;
– by removing shavings.
The thread working is normally performed by forcing the screwing of threaded tools (specially shaped and hardened) on the cylindrical surface of the body to be worked. Promid realizes metric threads on holes through two different working methods depending on the morphology of the piece:
• thread made by removing the shaving, with the aid of a column electric thread machine.
• thread made by rolling, through the punching machine TRUPUNCH 3000. In both of the aforementioned cases a pre-hole is made with the diameter established by the relevant provided tables.