The bolt is a simple washer with a simple square. On my frames i use washer with 1,6mm diameter for the lower timber and 1,4mm diameter for the upper timber. To get it was a mission, a challenge. I did varous test with different techniques but if you need 2000 or 3000 you need a very good method. Finaly i tested this punching tool and it works very good. You have only to punch 2x the rings (outside and the hole) and put the squarebolt inside. Thats all. Its simple, but its cost a lot of time und meine Nerven to find out the correct way.
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