If it is possible to specify particular HSN code, rates can be provided.
However I did a search for Tower Bolt and its falling under chapter 8302, even other items you mentioned are covered under same heading.
Tax for list of item you specified are taxed at 28%.
Extract from rate list issued:
8302 Base metal mountings, fittings and similar articles suitable for furniture, doors, staircases, windows, blinds, coachwork, saddlery,trunks, chests, caskets or the like; base metal hat-racks, hat-pegs, brackets and similar fixtures; castors with mountings of base metal; automatic door closers of base metal are taxed at 28%.