Abstract: A thread (2) of a fastener (3) such as a screw, a bolt or a nut is checked with respect to damages. Light beams are directed onto the thread (2) in a way that the light beams are directed substantially perpendicular with respect to a flank (17) of the thread (2). Then, the light beams being reflected by the flank (17) of the thread (2) are collected in a direction substantially perpendicular to the flank (17) of the thread (2) with at least one collecting optical system (18). The collecting optical system (18) has an optical axis (12) which is directed substantially perpendicular with respect to the flank (17) of the thread (2). In this way, it is possible.to reliably differentiate damaged surfaces of the thread (2) of the fastener (3) from undamaged surfaces at great inspecting velocities.

Abstract: A fastener (1) includes a screw (2) and a supporting element (3). The screw (2) includes a head (4), a shank (8) and a threaded portion (12). The threaded portion (12) is located on the shank (8). The threaded portion (12) includes a thread having an outer diameter (14). The threaded portion (12) includes a thread runout (25) facing the head (4) of the screw (2). The shank (8) includes a shank portion (10) having a diameter (11) which is smaller than the outer diameter (14) of the thread. The supporting element (3) is captively connected to the screw (2), and it includes at least one narrow location (27). The narrow location (27) has a diameter (28) which is smaller than the outer diameter (14) of the thread. The narrow location (27) includes at least one surface element (30, 35) facing the thread runout (25) and forming an enveloping cone (31) enveloping the thread runout (25) to prevent the supporting element (3) from getting clamped at the thread runout (25) of the screw (2).

Abstract: A fastener (1) includes a screw (2) and a supporting element (3). The screw (2) includes a head (4), a shank (8) and a threaded portion (12). The threaded portion (12) is located on the shank (8). The threaded portion (12) includes a thread having an outer diameter (14). The threaded portion (12) includes a thread runout (25) facing the head (4) of the screw (2). The shank (8) includes a shank portion (10) having a diameter (11) which is smaller than the outer diameter (14) of the thread. The supporting element (3) is captively connected to the screw (2), and it includes at least one narrow location (27). The narrow location (27) has a diameter (28) which is smaller than the outer diameter (14) of the thread. The narrow location (27) includes at least one surface element (30, 35) facing the thread runout (25) and forming an enveloping cone (31) enveloping the thread runout (25) to prevent the supporting element (3) from getting clamped at the thread runout (25) of the screw (2).