Brian Morris, 59, from Llanbadarn Fynnyd, was working at Stagecraft Display Ltd’s factory just outside Llandrindod Wells when the incident happened on 23 February 2012.
Llandrindod Wells Magistrates’ Court was told on 21 January that at the time of the incident Mr Morris had finished sawing for the day and his last task after an 11-hour shift was to clean the saw and saw well.
He stopped the machine and opened the door of the well while the blade was still running down and was on one knee blowing air into the well to clear the dust. At the same time a forklift truck drove into the factory and he turned his head to look.
As he did so the moving blade caught the sleeve of his work jacket and cut his right arm. Although he managed to pull himself free, the arm was almost wholly severed.
Mr Morris was taken to hospital, where he remained for a month, but doctors were unable to successfully reattach his arm and he underwent an amputation below the elbow.
He was unable to return to work because of his injuries and has since died from an unrelated illness.
A Health and Safety Executive (HSE) investigation found that although the machine was fitted with an interlock that stops power to the saw when the door to the saw well is opened, the saw took more than 30 seconds to stop completely.
The court was also told that a self-employed machine maintenance engineer inspected the saw three months before the incident and told one of the company’s managers that it should be taken out of service or fitted with a brake which would stop the blade much sooner.
Stagecraft Display Ltd, of Esgair Draenllwyn, Llaithddu, Llandrindod Wells, Powys, was fined £10,000 and ordered to pay £11,865 in costs after pleading guilty to breaching Section 2(1) of the Health and Safety at Work Act etc 1974.
A Stagecraft representative said: "The safety and well-being of our employees is a priority for our company. Since the accident nearly three years ago we have moved to new and modern premises. As we continue to expand and invest, H&S procedues are integral at each and evry stage and indoctinated into our team.
"We now have one of the most modern manufacturing facilities in the industry where we are designing and developing new retail systems to the highest standards expected by our customers."
The representative added that the company had undertaken a full reveiew of its H&S systems and appointed a dedicated person to implement them.
Speaking after the hearing, HSE inspector Damian Corbett said: "This incident was entirely preventable. Saws cause the most injuries in the woodworking industry and power-operated circular saws are dangerous machines which have caused many serious incidents.
"Employees should not be able to gain access to dangerous parts of the machinery while they are moving and Stagecraft Display had a duty, as do all employers, to ensure that this cannot happen.
"Unfortunately in this case the saw had not finished rotating despite the fact that Mr Morris had switched it off and he then inadvertently came into contact with the moving blade, suffering a horrific injury."