Friday, January 18, 2013

What is the Correct Wall Thickness of Extrusions When Tapping?

What is the Correct Wall Thickness of Extrusions When Tapping?


We are often asked what is the correct hole size for roll form taps.  This information is readily available through a variety of outlets including our website, tap manufacturer catalogs, wall charts, etc.   In addition to the correct hole size it is also important to have the correct wall thickness so the threads do not break through the extrusion walls.  So what is the correct wall thickness when tapping extruded holes?

The general rule of thumb is to have a wall thickness that is two times the pitch of the tap.  For example if a ¼-20 tap is required, each thread/pitch of a 20 thread per inch tap is .050.  If we multiply the .050 by 2 we arrive at a wall thickness of .100.  Determining wall thickness with metric taps is even more straight forward.  Just multiply the pitch of the tap by 2 and you will determine the wall thickness.  For example, an M6 x 1.0 tap would require a 2mm thick wall(1.0 x 2).