Hand Tools Archive

Re: One step back (with the Lingerie Chest)

Sgian Dubh
Clint, I think people sometimes get the wrong end of stick regarding sprung joints, which I'm not saying is necessarily what you are doing. It's just convenient to reply your post.

I think Derek reasonably deduced he had 'oversprung' the failed joint. It's hard for me to tell from the photographs provided, but I take his word for it. Creating too great a hollow between the edges is a real cause of likely failure. The ideal spring is one that requires no more than light pressure to bring the two edges together at the centre. Light pressure I define as only that needed to hold something like a large old fashioned telephone directory spine upwards and pages down between a finger and thumb.

Whilst it's true that wide thick boards have more strength (beam theory) than narrow thin boards, the spring gap generally can be adjusted to account for this when executing this type of joint, whatever the width and/or thickness of the boards. In any case, whatever type of boards are being joined (wide and thicker, or narrow and thinner) I generally prefer a sprung joint at assembly time because I know if extra pressure is needed to pull the ends of a panel together to close a gap, these are likely places for failure later when the item is in service. I prefer pulling up the centre a tiny bit tighter, if required, than sucking up the ends tight to close gaps. Slainte.

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