next split nuts 3 divided in two are fitted so as to envelope the outer circumference of threaded shaft 1 and the nut setting ring 2 the nut setting ring 2 is fitted into a locking groove 32 fig1 provided at the inner circumference of the split nuts 3 and the inner screw 31 of the split nuts 3 is fitted to the thread of threaded screw shaft 1 thus the split nuts 3 divided in two are held in the assembled state in one body at a desired position of the outer circumferential part of threaded shaft 1 by the fitting of the locking groove 32 at the inside and the nut setting ring 2 next a lock nut 4 is put around the threaded shaft 1 and also threadedly engaged with the outer thread 3b on the outer circumferential part of the split nuts 3 and both split nuts 3 are tightened by turning the lock nut 4 then a gap 6 exists at a joining portion between the two split nuts 3 and further because the outer screw 3b on the outer circumference of the split nuts 3 is formed in a taper surface and the inner screw 4a of the lock nut 4 corresponding to the shape of the outer screw 3b the split nuts 3 are tightened and fixed strongly on the screw shaft 1 by turning the lock nut 4 in order to release the lock of the lock nut device the lock nut 4 is turned in the.