These workshops are almost a paean of praise to the self-sufficiency of Gilfach Ddu: the variety and size of the machinery on display also gives some idea of the technical abilities of the staff employed here. In the repair workshops you can see many unique items from the Museum's collection. Among them there is a riveted boiler for a narrow gauge engine. This boiler was built in the company's boiler workshops at Port Dinorwic, and it gives you some idea of the high standard of craftsmanship needed to make a boiler out of riveted plates — one which could withstand a pressure of over 25kg to the square cm. On one of the other benches you will see a number of cans and tins, including the small round tins which were used to pay the quarrymen. These were made by the quarry's tinsmith, and were mainly used to store paraffin or oil of different sorts. Here too you can see a pump used to drive water up to the quarry hospital, some 500 metres away.

In the machine shop there is a lathe dating from 1900, used for turning all sorts of things — from the incline drum's wheels to turntables. There is also another lathe, 6.4 metres long, used to turnthe transmission and propeller shafts for the company's fleet of steam ships. The slotting machine, on the other hand, was used to cut keyways in gear and pinion wheels, sprockets and drive pulleys. There is also a rope-weighing scale. The quarrymen themselves paid for their ropes and were responsible for caring for them (as well as their explosives, their chisels and other tools). So it paid them to take great care of ropes which would be bearing their whole weight — sometimes on a rock face hundreds of metres high.

Most of the machines to be seen in these workshops could still do a good day's work, and indeed some of them are still used from time to time.