router bit for birds mouth spar

[Charles Neuman]

To make a hollow birdsmouth spar, you could use a table saw.

Or you could do it on a router table using a router bit like this one:

http://www.eagle-america.com/images/products/fullSize/v190-2865.jpg

( click for product description (http://www.eagle-america.com/html/catalog/productGroup.asp/314158) )

For an 8-sided spar, you need the 45/45 bit. For that case, why not just use a 90-degree V-grooving bit, like this one?

http://woodworker.com/images/ss/20-100.jpg

( click for product description (http://woodworker.com/cgi-bin/FULLPRES.exe?PARTNUM=129-191) )

I suppose a disadvantage of this bit is that you are cutting the surface that goes against the table surface. With the top bit, you are cutting the surface that goes against the fence, so you could adjust your outfeed fence so that you always maintain contact with the fences.

Anybody have any experience with either one?

Thanks,

Charles

[ 04-01-2005, 05:12 PM: Message edited by: Charles Neuman ]

[batory]

More birds-mouth bits
read the instructions at the bottom of the page

http://www.leevalley.com/wood/page.aspx?c=2&p=45160&cat=1,46168

[Keith Wilson]

I made my last mast (8-sided birdsmouth) using a 90-degree V-grooving bit exactly like the one you show. I made a little wooden guide that bolts to the face plate of the router to hold the bit in the center of the piece. No router table, just run it along the staves. Easy, cheap, and simple.

[ 04-01-2005, 05:53 PM: Message edited by: Keith Wilson ]

[StevenBauer]

I think the tablesaw is easier. You do have to make two passes but setup time is quicker.

Steven

[Venchka]

Based on just looking at the illustration above and Carlson's Mast program, it appears that the table saw 90^ cuts with extra material outside the joints yields a more uniform and thicker wall. Could be an optical dillusion. It needs to be checked out.

Wayne
In the Swamp. :D

[Frank Wentzel]

I've used the Lee Valley bits and I am quite satisfied. Be sure you download their instruction booklet. There is a lot more to the birdsmouth system than you might think. Note: Lee Valley bits are also $10 less expensive and of excellent quality - AND THEY ARE NOT MADE IN CHINA!!!!

/// Frank ///

[Bill Perkins]

That's an interesting point Jeff; hadn't thought of that . I'm downloading the instructions .

[landlocked sailor]

I have used a tablesaw with the blade tilted, a tablesaw with a moulding cutter and a router with a v-cutting bit. I think the tablesaw with the tilted blade was the easiest. Make sure you use featherboards to hold the stave to the table & fence. Rick

[Dave Gray]

Call me dense (many people have), but I do not understand the Lee Valley instructions:

-----------------------------------------
Bird's-Mouth Joinery Bits™
.......
Cylinders: Calculating the Width of the Staves

Once the number of sides and diameter have been determined, the width of the staves can be calculated. You can use one of the formulae below to determine this dimension.


6-sided object: Width = Diameter 1.7
8-sided object: Width = Diameter 2.4
..
---------------------------------------
Is there supposed to be a multiplication symbol there?

Dave

[Bill Perkins]

The division symbols ( must be a better word )have been left out of the whole document .

[Dave Gray]

Thanks Bill, division would make more sense than multiplication. I guess Lee Valley should revise the document. If you look through it, you see things like:

Chest Lids; Calculating the Number of Staves
6-side cutter: Number of Staves = 6 Height Depth + 0.2
....

Chest Lids: Example
Diameter = Depth Depth 4 Height + Height

It's enough to implode my poor mind on a Saturday morning.

[Joel Herzel]

The easiest way I found was to put a molding head with a v cutter on the table saw. High feed rate and hands nowhere near the action. Use a feather board on the side and above the workpiece. The workpiece is vertical.