hey bharat nice work. we wont be scaling the model up. we keep it the same as before (60*40). So the screw specs also remain the same which would be as follows:
15 cm Diameter
3 cm depth (4.5 inner and 7.5 outer radius)
50-60 cm length( we need to optimise on the length)

do not tell the guy to make the screw just yet. find out which material the mould is. find the cost. find out how much time he will take to make it, the cost, his address and post everything up the blog.