fig3 shows the stitching head which has been used for chain stitching using the dual needles and dual loopers as detailed in fig2 a hemispherical mandrel 1 is attached to the machine in such a way that it holds the hemispherical leather segment 2 firmly against the hemispherical cup fixed to the indexer shaft the hemispherical mandrel 1 is freely mounted on a ball bearing support 3 which helps the indexing movements of the leather segment the gear box 6 is suitably designed along with a pair of timer pulleys 7 to provide suitable speed to the needles the clutch motor 9 drives the gear box through v belt 11 also see fig4 the indexer assembly see fig5 consisting of a worm 19 and worm wheel 20 is used to hold and provide indexing motions to the hemispherical leather segment 2 with respect to the reciprocating needle movements a stepper motor 17 has been used to drive the indexer shaft locking mechanism 16 is provided for locking the indexer assembly 12 while stitching an electronic control unit is provided to maintain a fixed number of stitches over the circumference of the leather segment an encoder 14 mounted on the rear end of the indexer shaft is used to obtain accurate indexing and thereby uniformity in the spacing of the chain stitches an optical sensor fixed on the upper part of the body of the stitching machine is used to sense the position of the needle with respect to the leather segment as soon as the needle moves out of the leather.