Shinwa was established in 1971 when three competing manufacturers of traditional sashigane squares in Sanjo, Niigata joined together to form a single company.
To understand why that matters, it helps to understand just how important the sashigane is to Japanese woodworking — and particularly to traditional carpentry.
The sashigane is far more than a simple right-angle square. It has long been one of the fundamental layout tools of the Japanese carpenter, used for measuring, marking, calculating angles and laying out complex timber work.
Its importance is reflected in an old description of the tool as “the spine of the carpenter”. Alongside the sumitsubo, or ink line, it has become one of the enduring symbols of Japanese carpentry.
Shinwa and the Sashigane
Today, Shinwa produces an enormous range of precision measuring equipment, but for us the sashigane remains the jewel in the crown.
The company grew out of specialist Sanjo manufacturers already deeply involved in making these traditional squares, and that heritage remains visible in the extraordinary range Shinwa produces today.
Some sashigane are beautifully simple metric measuring tools. Others retain traditional Japanese scales and specialised markings that allow an experienced carpenter to perform calculations directly from the tool.
Whatever the format, the basic requirement remains the same: it has to be accurate.
Visiting the Shinwa Factory in Sanjo
I had the privilege of touring Shinwa's sashigane and ruler factory in Sanjo, and it was one of those visits that gives you a completely different appreciation for an apparently simple tool.
At one end of the process is a coil of stainless steel.
At the other is an accurate measuring instrument with precisely formed edges, carefully applied scales and a surface designed to remain readable through years of workshop use.
Watching that transformation happen was fascinating.
What stood out immediately was the combination of cleanliness, precision and ingenuity throughout the factory. Some of the machinery had been in service for more than 50 years, yet it remained part of an extremely controlled modern manufacturing process.
Accuracy Is Checked, Not Assumed
A measuring tool is only useful if you can trust it, so quality control sits at the heart of the process.
Every tool produced at the Sanjo factory is individually inspected.
Beyond that, Shinwa explained to us that a further sample of approximately 7% of production is removed from the line and subjected to additional measurement against master references in a controlled environment.
Those checks can include:
- Squareness
- Flatness
- Overall length
- Accuracy of the measuring scale
It is an impressive level of attention for a tool that many of us might otherwise take for granted.
How Do They Put the Scale on So Accurately?
This was one of the parts of the factory we were most curious about.
Unfortunately, it was also one of the parts we were not allowed to film in detail.
The exact process Shinwa uses to apply its surface treatments and measuring scales is understandably something the company keeps close to its chest.
Our basic understanding from the visit is that the rulers and squares receive a UV-reactive coating before being aligned with a master scale template.
The assembly is then exposed to ultraviolet light, allowing the scale to be transferred with a very high degree of precision.
From there, the tools go through additional surface-treatment stages designed to improve durability, scratch resistance and readability while reducing unwanted reflections.
We were able to film parts of that process, but some of the cleverest bits remained firmly off-camera.
A Surprisingly Sophisticated Tool
At first glance, a sashigane can look like nothing more than a thin stainless-steel square.
Spend some time with one and you begin to understand why Japanese carpenters have relied on them for generations.
A traditional sashigane can carry far more information than a straightforward metric scale. Depending on the model, its markings can be used for proportional calculations, diagonal measurements and traditional layout methods connected with circles, roof work and timber framing.
Some of these functions rely on relationships derived from geometry, including square-root and circumference calculations, allowing the carpenter to solve practical layout problems directly from the tool.
That depth of information is part of what makes a traditional sashigane so fascinating — but it also means that not everybody needs the most complicated version.
Metric, Traditional, or Both?
For Australian woodworkers, we have deliberately built our Shinwa range to include several different approaches.
If you simply want an exceptionally useful workshop square, a metric-only sashigane is a wonderfully straightforward option. You get the thin, flexible form and accuracy of the Japanese tool without needing to interpret traditional calculation scales.
For woodworkers interested in traditional Japanese carpentry, we also carry sashigane marked in sun and bu, along with models that retain more of the traditional layout scales.
Neither approach is inherently better. It simply depends on whether you want a highly accurate everyday square, a traditional layout tool, or something that lets you explore the deeper measuring systems used by Japanese carpenters.
Why We Like Shinwa
Shinwa makes the sort of tools that can easily disappear into the background of a workshop.
There is no dramatic cutting edge, no beautiful forged lamination and no shower of shavings when you use one.
You simply put the tool against your work, make a mark and trust that the mark is where it is supposed to be.
And that, of course, is exactly the point.
Good measuring tools remove uncertainty. They become quiet reference points that everything else in the project is built from.
After seeing the amount of thought, machinery and quality control involved in making Shinwa's sashigane and rulers, we have an even greater appreciation for the apparently simple stainless-steel squares sitting on our shelves.
Explore the Shinwa Range
Whether you are looking for a simple metric square, a traditional Japanese sashigane or an accurate ruler for everyday workshop use, there is a Shinwa measuring tool to suit the job.
