4 9 such irregularities can make it easier for the thread removal head to make direct contact with the thread ends and also give the thread removal head a larger total surface area and thus larger working surface for the material in the thread removal head in the case when it is made from a material that u201c grips u201d as above for example the surface can be configured as a bumpy surface see fig2 and 7 or as a grooved surface see fig4 5 6 8 and 9 the bumps 5 the space between them the grooves or slots 7 and the space between them can have adapted characteristic dimensions typically being in the range of 1 5 mm the grooves or slots as shown in fig4 and 5 can lie in the circumferential direction about the common lengthwise axis of the shaft 1 and thread removal head 3 i e each groove or slot will lie in a plan perpendicular to the lengthwise axis the grooves can also have a different orientation such as in the lengthwise direction of the shaft 1 i e strictly speaking lying in a plane passing through the lengthwise axis of the shaft see fig8 or they can also extend in helical manner over the thread removal head 39 s surface with a suitable pitch angle e g in the range between 45 u00b0 and 60 u00b0 in relation to the lengthwise axis of the shaft see fig6 the grooves.