The phrase "iron hand" refers to someone who has strong and strict control over a situation or people. It implies that they are strict, firm, and not easily swayed or influenced. Full definition
A well with a cast iron hand - pump yields fresh, cold water, carried to the cottage in buckets for drinking, cooking and washing up. (moneysense.ca)
Made from cement and brass, it features brass coated iron hands and is finished soft, brushed concrete. (livingetc.com)
The GT8 is a colt that has never before felt saddle and bridle — its equipped with harder springs, stiffer dampers, tauter bushings, more aggressive brakes and almost as much carbon - fiber wing work as a Le Mans car — and is best treated with iron hands in velvet gloves to avoid any unexpected understeer scrubs or snap - oversteer situations. (automobilemag.com)