regarding clarification in leather job work

Dear sir, I am doing leather job work for shoe factories. They gave me the wet blue hides for processing. I will buy chemicals for job work at the gst rate 18% & 28% and used it in the above job work process. I used machinery process also and it is comes under 5% gst.
usage ratio is chemicals70%, machinery 30% Pls advice what will be gst for us? and hsn/ sac code also