「河合継手」は木材の先端を複雑な形状に削ることによってパズルのように組重なり結合します。

「河合継手」は他の接ぎ方と違う最大の特徴は、3方向から木材を繋げられる点です。

工学院大学建築学科の河合直人教授が東京大学の学生時代に課題として提出したもので、建築材としての実用性を重視して考え出されたわけでは無いようです。

シノブ・コバヤシさんが、「河合継手」に挑戦してみた画像がインスタグラムにアップされ、海外で話題になっています。

instagramより

I need more practice but…I think I have done enough joinery for now. #capellagården #woodworking #joint #joinery #japanesejoinery

Shinobu Kobayashiさん(@shino_bunny)が投稿した写真 – 2014 9月 19 12:14午前 PDT

And this is the inside of joinery and done by all hand work…Takes time, but great woodworking practice. #capellagården #joint #joinery #japanesejoinery #woodworking

Shinobu Kobayashiさん(@shino_bunny)が投稿した写真 – 2014 9月 19 12:33午前 PDT

This Japanese joint called "Kawai tsugite" invented by Japanese professor when he was in Tokyo university. It is not popular Japanese joint and wanted to share to woodworker all over the world by Instagram. Me and Tais he is master cabinet maker from Denmark found the way of this joint so we tried while we have joinery workshop at Capellagarden. #capellagården #joint #joinery #japanesejoinery #woodworking

Shinobu Kobayashiさん(@shino_bunny)が投稿した写真 – 2014 9月 19 12:48午前 PDT

Since many people interested in this "Kawai tsugite", I would like to share how I have done with some photos. This is the lines you need to marked out on meterial. Black part is needed to be remove. #joint #joinery #japanesejoinery #woodworking #capellagården #cabinetmaker #継手 #木工 #技

Shinobu Kobayashiさん(@shino_bunny)が投稿した写真 – 2014 9月 22 1:41午後 PDT

Once you marked out, you will be able to see that you can cut the whole of corner. I think you can use machine for this, but I used only hand saw and hand plane to make perfect triangle. Then you need to marked out three triangles like photo shows. It needs to be absolutely same three perfect triangles. #joint #joinery #japanesejoinery #woodworking #cabinetmaker #capellagården #木工 #継手

Shinobu Kobayashiさん(@shino_bunny)が投稿した写真 – 2014 9月 22 1:49午後 PDT

Then you need to take middle part of waste. Same as others but bit harder. Once you have done, all of three positive triangles and three negative triangles, total six of them HAVE TO BE EXACT SAME. #joint #joinery #japanesejoinery #capellagården #cabinetmaker #木工 #技 #継手

Shinobu Kobayashiさん(@shino_bunny)が投稿した写真 – 2014 9月 22 2:19午後 PDT

I could just record 15 seconds of movie so I have to move as quick as I can, but you might get some ideas from his video. If you are succeeded with perfect shape, then it should be fitted in three ways; 1. Straight joint 2. Corner joint 3. Other side of comer joint. I have fitted and unfitted many times for recording 15 seconds movie and joint become bit loose now, but it should be bit tighter if you did perfect joinery. And there are some tips to do it. 1. Need to be absolutely accurate with lines. 2. Need super sharp chisels. 3. Need to do practice a lot. 4 Need to be PATIENT. I spent almost 12 hours to do one set of joints at first time. In the end, I still spend around 6 hours to finish this. Good luck guys😉#capellagården #cabinetmaker #joint #joinery #japanesejoinery #木工 #技 #継手

Shinobu Kobayashiさん(@shino_bunny)が投稿した動画 – 2014 9月 22 3:11午後 PDT

From the other angle. Maybe much clear to see the joint. I hope the photos and videos I uploaded helps to get more skills, knowledges, ideas, and challenging spirits to woodworkers and cabinetmakers all over the world🇯🇵🇰🇷🇩🇪🇨🇳🇺🇸🇫🇷🇪🇸🇮🇹🇷🇺🇬🇧#joint #joinery #japanesejoinery #cabinetmaker #capellagården #木工 #継手 #技

Shinobu Kobayashiさん(@shino_bunny)が投稿した動画 – 2014 9月 22 3:59午後 PDT

宮大工などの世界には色々な特殊な組み方が存在し、パズルの様な中にも強度や芸術性が高いモノが多数あります。
新国立競技場で選ばれた建築家・隈研吾さんは地獄組みという、木材を多数組み合わせ、張り巡らせる技法が好きで多用しています。

おまけ・河合継手が色々な工具を使っても作るのが難しい事が良く分かる外人の荒々しい解説動画ｗ

YouTubeで一番人気があると思われる継手動画

金輪継（かなわつぎ）・伝統的継手の動画②_【小林建工_018】