Rule Joint

[Chris Padilla]

Am I correct in assuming that this can be cut with a typical roundover bit and it's associated "inverted/opposite" cousin cove bit? For example, a 3/8" roundover bit and 3/8" cove bit.

For those that aren't aware, a rule joint is typically used for a table leaf/extension that folds down.

I have a need for something like this although not for a table top....

[Jerome Hanby]

I think that's how Norm made the joint. I assume the cove and roundover are the same radius, but I don't recall that exactly.

[Jim Rimmer]

All of the bit suppliers sell table leaf bit sets but may be too many $ for a one time shot.

[Mike Henderson]

Yep, when I made one, I just used a roundover and a matching cove bit. No problems.

Just make a test cut first on scrap.

Mike

[David Winer]

Am I correct in assuming that this can be cut with a typical roundover bit and it's associated "inverted/opposite" cousin cove bit? For example, a 3/8" roundover bit and 3/8" cove bit.

For those that aren't aware, a rule joint is typically used for a table leaf/extension that folds down.

I have a need for something like this although not for a table top....
I used a rule joint for my dining room table about 35 years ago. The only tool I had for shaping the boards was a 12" radial arm saw and a molding head cutter set. This scheme worked (the table is still in daily use) but as I recall it was rather difficult. If I had to do it again I would probably use a router.

Also, as I recall, this type of drop-leaf requires a special hinge. (Butler table hinge?)

[Dino Drosas]

Not a butler table hinge. The rule joint uses a hinge with one arm longer than the other so that the center of the hinge is placed at the center of the round over section of the joint. This allows the leaf of the table to be able to roll up over the rounded section of the table edge to create a flat top.

[Dan Bowman]

The previous issue of Woodsmith had a piece on rule joints. The discussion of the hinge layout was quite helpful.

[John McClanahan]

Norm did it that way on last weeks new Yankee Workshop web cast. He used the type of hinged that Dino mentioned. I don't recall if he called it a rule joint, but he didn't always use proper names back then. He called the miter gauge a Tee Square.

John

[David Winer]

Not a butler table hinge. The rule joint uses a hinge with one arm longer than the other so that the center of the hinge is placed at the center of the round over section of the joint. This allows the leaf of the table to be able to roll up over the rounded section of the table edge to create a flat top.
Well put. Re-thinking why I had difficulty with the joint all those years ago, it was the hinge that gave the most trouble. I didn't have instructions for the special hinges and ended up installing by trial and error. Trials and errors to be more precise. With mortised-in hinges--arrgh.

[mike holden]

Center point of the hinge should be at the center of the arc of the roundover.
To be geometrically correct, the cove should be larger by the clearance between the panels, but, in practice; using matching radii works fine.
Note also that the fillet above the roundover needs to be larger than the fillet above the cove to avoid interference when leaf is in the upright position.

Mike