The Shinwa brand was formed in 1971, after three competing Sanjo-based makers of traditional sashigane squares merged to form a single company.
Before continuing, it is important to mention the importance of the sashigane to Japanese woodworking, and especially to Japanese carpentry. It so foundational that it is referred to as "the spine of the carpenter", and has become a symbol of the craft, along with the sumitsubo (ink pot).
With hundreds of years of experience, Shinwa has grown to produce countless accurate measuring tools and many related products, of which it's sashigane range is the jewel in the crown. It is the only company making traditional Sashigane in Japan.
I had the privilege of getting a tour of the Sashigane and ruler factory in Sanjo. It was absolutely amazing to see a coil of stainless steel transformed into a precision tool.
Every single tool produced in this Sanjo factory is individuly quality controlled and, beyond that, a further 7% of everything that comes off the line is taken out of the batch and measured for squareness, flatness, length, and scale against a master reference in a controlled environment.
Shinwa told us JTA is the number one international importer of Sashigane. They may be blowing our trumpet, but they told me the genius and usefulness of this tool are not normally realized outside Japan.
I was not allowed to film any of the processes on how Shinwa applies the surface coating and more importantly how Shinwa applies the scale with extreme accuracy.
My basic understanding: the rulers and squares are coated with a UV reactive layer, then placed over a template with the scale marked on it. The template and square is then placed in a UV light box and the marks transfer onto the surface. The rulers and squares go through several other surface coatings for scratch-resistant, durable, and anti-reflective. Some of this I was able to film.
If you are looking to add a sashigane to your workshop, we are always adding to our range of beautiful squares. While traditional sashigane carry calculation-based measurements using pythagoras' theorem or pi-based units, we have also added a number of Shinwa's simpler metric-only sashigane to our range, not to mention a couple that measure in the traditional sun and bu based increments.
