If you build chairs, staked furniture or anything that uses round tenons, this entry is for you. One of the greatest joinery tricks I know of is to cut your tenons slightly oversized – .010” or a bit more and compress them slightly before assembly.
This trick ensures tight fits, which are essential for tenons that don’t have a shoulder, or when building chairs where the joinery is going to be abused.
I used to do this by wrapping blue tape around the metal jaws of my locking pliers. Then a reader took pity on my goofy wheeze and sent me a pair of Tamiya non-scratch pliers. These $32 pliers are just like regular pliers but they have nylon jaws that refuse to chew up the tenon when you compress it. You squeeze the pliers and rotate the tenon, which is smoothly compressed.
So, what about square tenons? You can compress those as well, though the pliers aren’t the best method. Instead I’ll clamp the tenon cheeks in a metalworker’s vise. That will do the same job without too much fuss.
So, what happens to the compressed tenons during assembly? The water in the glue wicks into the joint, swelling it and locking things up. I have found that the reaction is even faster if I use hot hide glue – the water and heat swell up the wood quickly – much like when you steam out a dent on the corner of a piece of dented wood.
— Christopher Schwarz
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For compressing rectangular tenons away from a bench with a vise, you might try Knipex Pliers-Wrenches. As the name implies, they are are like a marriage between an adjustable wrench and a pair of pliers. The jaws are smooth, and remain parallel as you close them on the work piece (or a hex head fastener). They have astounding leverage, and are extremely well built.