The HSE said a suitable and sufficient assessment of the work equipment provided would have shown that the skates used were unsuitable for the work.
The company pleaded guilty to breaching regulation 2(1) of the Health and Safety at Work etc Act 1974.
It was fined £80,000 and ordered to pay £6,713 in costs at a hearing at Preston Magistrates’ Court.
HSE Inspector Anthony Banks said: “This company’s failures resulted in the death of a much-loved young man.
“Those in control of work activities, including the movement of heavy machinery from one part of a site to another, need to assess the risks of that work, and plan a safe way to undertake it.
“This tragic incident could have easily been avoided with the right controls in place”.
A spokeswoman for Partwell Special Steels Limited said their thoughts and prayers were with Mr Borthwick’s family and the firm was “devastated by his loss”.
She said nothing like this had ever happened before and the firm had “made improvements” and was “committed to ensuring it does not happen again”.
“Connor was a much-loved and respected member of our team and is greatly missed,” she said.
“His sense of humour and hilarious anecdotes always brought a smile to our faces.
“As a small family business, we care deeply about the health and safety of all our staff and continue to feel his absence.”
Staff would “continue to celebrate his life by raising money for the charities he has chosen”, she added.
