By using a clamping part with clearance hole, thicker stack-ups with up to four layers can be joined with flow drill fastening. The upper layer can be aluminum or even high-strength steel (HSS). Since no upcoming material needs to be accommodated by the joining element, a cheaper flat head fastener can be used. However, the position of the robot is very important to exactly meet the clearance hole. If used with adhesive, a stitch bead application is recommended to avoid squeeze out.
This joint variant is suitable for body-in-white applications when the design of the car body does not allow direct joining. Also, it is used for applications where serviceability is a priority, for example when joining the cover to the tray in battery assembly for electric vehicles. Due to the clearance hole in the cover sheet, the cover can be easily disassembled and reassembled several times and remain leak tight.