“You can complain because roses have thorns, or you can rejoice because thorns have roses.”Tom Wilson
This tool is a specialty mortise chisel with two blades for cutting twin mortises at the same time. It was developed specifically for cutting mortise joints in wooden stiles and rails for doors, shoji, cabinets and other joinery.
Interestingly, double or twin tenons are not called ” nihon hozo” (hozo means ” tenon”) but “ nimai hozo “ (二枚ほぞ) with “ni “ meaning 2. In this case the number is combined with the counter “mai “ used to count flat things like a sheet of paper or tenons. Japanese is almost as messy as English… I blame those pesky Buddhist priests for the complications involved in reading and writing Japanese, but I’m not sure who to blame for English.
The name is a variation of the name of the standard mortise chisel ” mukomachi nomi” in my previous post, and no, I still don’t know what it has to do with ” waiting over there.” In front of this is added ”nihon” (二本) with ” ni” meaning ”2” and ” hon” being a counter for longish things, like pencils or trees, or in this case, blades. The word is pronounced ” knee hone.”
Allow me to wander off the path a bit and talk about the Japanese language since you might find a few details interesting. If you don’t feel international today, please feel free to jump over the next few paragraphs.
The nation of Japan is called “Nihon” or “Nippon “ in the Japanese language and is written with the two characters “Ni “ 日 and ”Hon” 本 sometimes pronounced “pon.” Yes, the same pronunciation and one of the same characters used in nihon mukomachi nomi. Besides being a counter for pencils and trees and longish things, it also means ” book” and ” source. ” The word for the nation of Japan means “The source of the sun,” a jab by the Japanese at an arrogant Chinese emporer some millenia ago.
Spoken Japanese is not that difficult for English speakers to figure out, but the reading and writing are crazy difficult because of the vast quantity of Kanji, the multiple pronunciations possible for most of them, and the multiple meanings attached to many.
Elementary children are required to learn 1,006 kanji characters along with the various meanings and pronunciations. In total, a minimum of 4,272 characters are used in newspapers and magazines and must be learned before graduating middle school. Most educated people in Japan can read well over 6,000 of the over 13,000 registered kanji in Japan. Universal literacy requires a lot of study and memorization at a young age. This should give you an idea why education is so highly valued in Japan.
When I was a young missionary in Japan in the 1970’s, I spent several months stationed to Ehime prefecture in rural areas of the island of Shikoku, back when many farmhouses in that locale still had thatched roofs, no glass windows, and no electricty. Many of the older residents had spent their entire lives on their little farms and could not read or write, and had never seen a brown-haired blue-eyed foreigner before.
But the children in these mountain villages were always excited to see a foreigner and would swarm around and ask us where we were from. My standard response to this somewhat rude but innocent question was to point down at each of my legs and count them saying ”One leg, two legs. I’m a Nihonjin.” The “nihon” I was was jokingly referring to was the same as the mortise chisel which is the subject of this post, not Japanese Nationality which is pronounced identically.
Now you know a stupid pun in Japanese, so never say you didn’t get your money’s worth at this blog!
The twin-blade mortise chisel is exceptionally difficult to make, and even new ones require the owner to perform a significant amount of tuning to convince them to perform well. They have never been common, and I am not aware of anyone forging them now.
The twin tenons this chisel specializes in cutting are almost twice as strong as a larger single tenon, and are the preferred joint for high-stress wooden connections worldwide, especially joints in doors and windows. If you haven’t tried them before, you should. They look pretty cool as through tenons too.
Twin tenons have three advantages that justify the extra work. First, while they may have the same or even less cross-sectional area, they have more surface area than a single tenon in the same space, creating greater friction when assembled, if properly cut, creating a joint that is much more likely to stay assembled when stressed.
Second, this larger surface area also means a larger glue area, a big advantage with the right glue.
And finally, twin tenons are much more resistant to twisting, an huge advantage for highly stressed joints in operable doors and windows. This is their biggest advantage and is nothing to sneeze at. If you want a door to last, always use twin tenons, at least at the bottom rail.
I purchased one of these chisels many years ago. They are difficult to tune. But even after all that work, the gentleman I learned tategu work from many years ago was not impressed with my clever tool insisting that a regular mortise chisel does a better job. There is an obscure structural reason why this makes sense, which I will not delve into here, but I did not ask Mr. Honda at the time for an explanation because it would have been improper to question a master who had been a professional joiner at his level for 60 years.
I can’t get these chisels made anymore, and know of no blacksmith that makes them nowadays. The time is not far away when handmade tools will not be available except as collectors items.
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