John Flynn's grandfather, also called John, was a joiner who worked on the original staircase.
It was one of the most spectacular sights on board the most famous ship to sail from Belfast. However, Mr Flynn did not talk about the staircase often.
His grandson said: "I think at that time the workers would have felt deflated and let down to see their craftsmanship at the bottom of the sea."
Nonetheless, Mr Flynn worked on at Harland and Wolff throughout the 1920s. He died in 1941. His grandson John Flynn lived with his grandfather in Portrush for the last two years of his relative's life.
He keeps the joiner's tools at his home in east Belfast. His saw is engraved with the initials JF.
An inscription on the blade gives a sense of the pride which Mr Flynn took in his craft. It says "the beauty and finish of this saw is in excellence".
John has done some research on the saw. Judging by the crest, he thinks the tool dates from between 1906 and 1914. So it's possible this is the very saw which carved out the elegant ornaments and sweeping banisters on the Titanic's grand staircase.
The other tools in the box offer a glimpse into Mr Flynn's painstakingly detailed work - a two-foot ruler, a hammer, a brace. They may have been used not only on the Titanic, but also on its sister ship the Olympic - whose staircase Mr Flynn worked on too.
As Belfast prepares to mark the 100th anniversary of the Titanic's sinking, John and his wife Joan often think of John's grandfather and his colleagues who worked on the ship.
"Whenever we see the staircase, we feel nostalgia - to think he worked on that," John said.
"People always relate everything to the grand staircase - it's one of the most talked-about parts of the Titanic. We feel very proud, really, about this."