Yamamoto Rock Machine (Former Yamamoto Iron Works) Finishing Factory

Yamamoto Rock Machine Finishing Factory: Arched Windows for a Fitters' Shop

The Yamamoto Rock Machine (Former Yamamoto Iron Works) Finishing Factory (ヤマモトロックマシン（旧山本鉄工所）仕上げ工場) is a single-story timber workshop built around 1937 for a rock drill maker in Tojo-cho, Shobara City, Hiroshima Prefecture, and it was registered as a Registered Tangible Cultural Property on 25 February 2016. It runs parallel to the east side of the First Factory, 38 meters long with a building area of 417 square meters, under a sheet-metal roof crowned by a raised ridge vent, or clerestory monitor.

In Japanese machine shops, "finishing" usually means the stage after machining, when parts are trued up by hand and fitted together. If the name holds, this was where Yamamoto's drills took final shape as products. Fitting is close work, and it needs good light. The design of the finishing factory puts its effort into exactly that.

Why the Finishing Factory Was Registered

It was registered for contributing to the historic landscape. The Agency for Cultural Affairs describes it as an example of a prewar provincial factory that used Western-style design to bring in daylight. Two things are being recognized: the Western shapes and rhythm of the windows, and the fact that they were put to work lighting the shop floor instead of serving as ornament.

Comparing it with its neighbors on the Yamamoto Rock Machine site makes its place clear. The First Factory of 1934 split its span into three bays and raised the middle one, lighting the floor through clerestory windows and a ridge monitor. The Second Factory of 1937 spanned its width in one go with a king post truss. The finishing factory uses a queen post truss, with two vertical posts instead of one, and gives its gable-end windows segmental arched heads. Built within a few years of each other, the three workshops solve the same problem, getting light deep into a wide floor, in three different ways. Of the three, the finishing factory makes the clearest statement in Western-style design.

Early Showa factory buildings have tended to disappear, rebuilt in steel or concrete as production changed. A provincial workshop with a timber roof frame and Western window pattern, still in use by the company that built it, has real value as a record.

What to Look For at the Finishing Factory

The queen post truss sets two posts symmetrically on the tie beam and links their tops with a horizontal member, with diagonals carrying the roof. With no post directly under the ridge, the center stays open. Put a monitor on top, as here, and light comes in at the peak while trapped heat has a way out.

On the outside, look for the south gable. The windows there are topped with shallow segmental arches, softening the triangle of the gable wall. Along the east and west sides runs a row of vertically sliding sash windows, giving the long walls a steady rhythm. For a factory, the window pattern looks surprisingly like a school or an office.

Monitor, arched gable windows and side sashes bring light onto the workbenches from above, from the end and from the sides. If you get inside on an open day, notice how the light shifts over the course of the visit.

Visiting the Finishing Factory

The Yamamoto Rock Machine finishing factory stands inside the company's working Tojo plant and is not open to visitors. Because it sits within the factory block, the public road gives you glimpses of the roof and monitor at most, and how much of the south gable you can see depends on where you stand.

The interior has been shown only during tours held with the company's cooperation. It is a working shop with machinery in use, so follow your guide and ask whether photography is allowed. Do not enter the grounds without permission.