Drilling larger diameter holes in steel can be a challenge without the correct equipment. Normally s up to 13mm diameter can be drilled using a traditional hand drill, but holes larger in diameter are much more difficult to drill. Now using the impacta step cutters from Hole maker technology, it is a much easier and faster task.
https://holemaker-technology.com/collections/new-products/products/versadrive-impactastep-cutter-metric-sizes
HMT products are also now available on eBay-
https://www.ebay.co.uk/itm/265091507495?hash=item3db8af6527:g:yhkAAOSwEHJgUg8b