Andy Dingley wrote:
On Tue, 19 Jul 2005 16:29:57 +0100, "flash"
wrote:

I do have some thick timbers but they
are all three foot long, so what I want to do is join them together
somewho to make six foot posts.

Personally I'd find some new timber, long enough. The joints are too
much trouble.

Obviously you're hard-pressed to get six foot from two three footers,
unless you use a butt. That's not a bad way to do it, if you use steel
plates bolted on from either side.

A scarf is inappropriate for a vertical post. it will also lose the
most length. If you must, it needs to be a more symmetrical
birdsmouth (either halved or cornered) scarf, rather than a simple
scarfed lap. You could also use some form of stubbed scarf. None of
these are easy to cut.

Perhaps the best joint is another Japanese joint - jyuji mechigai
tsugi - the cross-shaped mortice and tenon. This is good from locating
verticals and it's also easy to cut. One face has a cross cut into it
by removing the four corners to leave a cross with arms about 1" wide
and 1" deep. The other is cut to leave four castellated areas with two
grooves between them.

Damn.

I saw a picture a while back on rec.woodworking of a Japanese temple pillar
done with a totally impossible dovetail butt joint cut in 16"+ timbers...

can't find it now :-(

I suspect it wouldn't be the sort of thing the OP was looking to do anyway
though ;-)