I am planning out an envelope table, and I've not seen one disassembled, so I am unfamiliar with the original mechanism used. I don't need ideas on how to do it - I know of several ways I could do it - but I would like to know how it was done back in the day.
The table I'm working on pivots so that when the leaves open, the corners of the frame support the leaves. I know where to get the hinges needed; it's the pivot mechanism I want to identify.
(Furniture Making Forum)
From contributor I:
As far as I can remember the envelope table rotates from the centre, however there is a little button around the inside edge that is powered by a spring. When you rotate the table, the button lifts one of the leaves to allow you to get a finger hold. Another method is to have a slightly beveled inside edge to one of the leaves so that when you lean on the outside of the top, the weight is enough to lift the top up.