Coupling of a head set

A head set comprising a steerer tube including an outer thread formed in an upper and outer portion thereof and a groove longitudinally formed in said upper and outer portion thereof, a sleeve threadedly engaged on said steerer tube, a ratchet gear engaged on said steerer tube and including a key extended radially inwards for engagement with said groove of said steerer tube, and a compression nut threadedly engaged on said steerer tube and engaged on said ratchet gear in order to compress said ratchet gear in place when said compression nut is rotated in an active direction, said compression nut including an annular shoulder formed in an inner and lower portion thereof for accommodating said ratchet gear, and a screw hole formed therein and communicated with said annular shoulder, and a screw threaded in said screw hole of said compression nut for engagement with said ratchet gear received in said annular shoulder, whereby, said compression nut is prevented from rotating in a reverse direction relative to the steerer tube.