Birdsmouth joinery

[Bill Sutherland]

Thinking about doing a 8 sided box using Birdsmouth joinery. Lee Valley has the bits for a router but I want to build mine with hand tools. Anyone know how to do this??

[Jim Koepke]

If you do edge grain to edge grain it shouldn't be too difficult to do it like this > https://sawmillcreek.org/showthread.php?157217

This became a birdhouse and has been out in the weather a few years.

Just looked up birdsmouth joinery. That joint could be cut with a rabbet plane. You might need to make a custom angle add on for the fence.

A Stanley #55 has fences that can be angled for this kind of work. Kind of an expensive investment for one project.

It likely wouldn't be difficult to use an wood body rabbet plane with a set up for the board to be moved over the plane instead of moving the plane over the board. That was one way coopers used planes when making barrels.

jtk

-Oops! Just realized you are not a contributor. You won't be able to see the images of my 22-1/2º shooting board for making an octagon.

[Scott Winners]

If you aren't tapering over the length, like the mast for a sail boat, just a box with a consistent width or profile, I agree with Jim you can do it with a rabbet plane. If you are going to taper over the length, say 10" wide at the base and 6" wide at the top with four inches of height you are going to need one keg of Guiness for design and layout, a second keg for execution and a third keg for glue up and clamping- because that math will hurt your head.

Without a Stanley #55 in stock I would lean towards a modern rabbet plane with an angled fence attached to the factory square fence. If you are going to taper it from base to top, one option is to build it big and then plane off the excess from the exterior- it has been done that way many times for sail boats.

If it is going to be same diameter top to bottom, do the math, use a square fence on your rabbet plane, and praise Jesus that you dodged a bullet.

[Bill Sutherland]

I was hoping to make a 8 sided box. Sounds like it’s going to be difficult to get consistent matching angles.

[steven c newman]

On the older Mitre Boxes...the Quadrant Scale does not have degrees( a later invention)....the numbers stand for how many sides to a box that you want to make...0 being a square ...there are some boxes out there that count up to 24 sides....I think there is indeed an "8" mark on that scale...

[Mel Fulks]

Steven, when I was in early grade school I asked several adults what those numbers were. They didn’t know ,or possibly didn’t want to try
to explain it to a kid. Now I know, Thanks Steven !

[Jim Koepke]

I was hoping to make a 8 sided box. Sounds like it’s going to be difficult to get consistent matching angles.

That is what a shooting board is for. A shooting board with an angled bed is often referred to as a 'donkey ear.' The link in my first post is to a post on how a 'donkey ear' shooting board was made to make an octagonal birdhouse, basically an 8 sided box.

If you want to do it wit a birdsmouth joint you could make the cut in a long piece of wood (at least 8 times as long as you want to make the box tall).

If taller than a foot you will have to use more than one piece.

It might be easier using a fixed plane with a shop made fence to guide the work over the plane.

This is all based on wanting an 8 sided box with all sides being equal. The birdsmouth would then be at 45º.

If you want to do some fancy sizing, then more planning is needed.

jtk

[James Pallas]

I guess I may be a little thick here. I saw articles a few years ago about this joinery. I thought about it a bit and never came to an answer of “why”. I could not and still can’t answer that. Could someone enlighten me or is it like the impossible dovetail? Just something to do, more glue surface, stronger than splines.?
Jim

[Thomas Wilson]

If you did actual birdsmouth joints using narrow stock to make rings with a bit of overhang on each joint and made a stack of them in decreasing size alternating the orientation of each ring, the result would look a pine cone. In my head this looks really cool.

[Jim Koepke]

I guess I may be a little thick here. I saw articles a few years ago about this joinery. I thought about it a bit and never came to an answer of “why”. I could not and still can’t answer that. Could someone enlighten me or is it like the impossible dovetail? Just something to do, more glue surface, stronger than splines.?
Jim

It is a router table joint, easy to make with a router table and a specific bit for the number of sides desired.

It does have more glue surface compared to an angled edge joint.

Only one edge has to be cut to for a birds mouth where coopered or angled edge joinery requires both edges to be cut.

jtk

[James Pallas]

It is a router table joint, easy to make with a router table and a specific bit for the number of sides desired.

It does have more glue surface compared to an angled edge joint.

Only one edge has to be cut to for a birds mouth where coopered or angled edge joinery requires both edges to be cut.

jtk

Thanks Jim. Kind of what I thought. Don’t have a router table and not interested in having one. Don’t find it too difficult to make coopered things with hand tools. I really think it could be set up and cut with a 78 if one wished to. Cant think of how I would use it. May find a use for it sometime. Keep it stored in the backlogs of memory for now.
Jim

[Scott Winners]

My understanding of a birds mouth joint is having a step on each piece makes clamping it up correctly a bit easier while the glue is wet. Gluing edge grain to edge grain is good, cutting 22.5 degrees on all the end grain would be the weaker glue joint. On a smaller piece like in Jim’s link clamping during glue up might be challenging but should be manageable.

On something like a 30 foot spar for a racing sail boat that is maybe six inches at the base and two and five eighths at the tip birdsmouth all the way.

for a small piece like the OP described I think it could be done as a birdsmouth with a 45 degree fence on a rabbet plane. I would be obsessing over making sure my depth stop didn’t flinch, and would put the rabbets on the longest possible stock. Cut pieces to length after the rabbet is cut.

[Scott Winners]

I have noticed different trades don't always use the same name for a joint, and often there are multiple correct names for one joint. The birdsmouth joint I have been babbling about in this thread looks like this one:

https://www.timbecon.com.au/torquata-birdsmouth-jointing-bit

A homebuilder of course thinks of a birdsmouth as a thing to cut in the underside of a rafter for a roof.

[steven c newman]

Imagine doing 8 sides using this joint..
469268
when done...looks like you somply folded a board into a box shape, using a hinge at each corner...
469269

469270
"Hinge"