Thomas Dudley is celebrating its centenary in 2020 but had already been forced to put celebrations on hold as a result of the pandemic.
Chairman Martin Dudley said the group, which includes its main foundry in Birmingham New Road and Masefield-Beta, McDonald Diecasting, Waterfit, Rugby Plastics, Ecosan and ZJP Plumbing Supplies, was consulting over 31 compulsory redundancies out of its 500-strong workforce.
On top of that it has invited voluntary redundancies and early retirement.
Mr Dudley said that combined it would see a reduction of about 20 per cent in the number employed across the group.
"Unfortunately all businesses are now having to look at what the structure of their business is going to look like going forward.
"It is incredibly hard for a family business like ours to make redundancies when we have so many people who have given many loyal years of service.
"Our sales dropped by 70 per cent in April and we had to furlough 70 per cent of our workforce. Although order books are now coming back it is now starting to cost us and we can't continue with the current level of people and the current level or orders," explained Mr Dudley.
He said the job losses were affecting all group companies and all departments.
"We are trying to maintain skills in the workforce as much as we can and we aim to keep all six of our apprentices," he added.
Mr Dudley said that senior management had taken significant salary cuts to help the group through the crisis and had had to make difficult decisions for the longer term.
"No one knows what the future will hold and if there is another round of the virus that could hit order levels again coming up to Christmas and Brexit," he added.
Most 100th anniversary events have had to be cancelled including a planned "away" day for employees which will not take place next year
"It is a very austere time within the business and everything has had go be put on hold," he explained.
The company did hold a Hawaiian Day on Thursday because of the high temperatures with some staff able to come in in Hawaiian-style shirts.
"It was to try and get a bit of good feeling going through the business. We don't want people to feel they have to be wearing sackcloth and ashes," added Mr Dudley.
Sales fell to 30 per cent of normal in April and have since recovered to 90 per cent in some parts of the group but only 50 per cent in others. They are currently at about 75 to 80 per cent across the group.
Thomas Dudley, which makes plumbing products, made protective face shields for the NHS during the height of the Covid-19 pandemic.