On Sep 21, 2:07 pm, whit3rd wrote:
45 degrees is always described (by careful persons) as 45 +/-
something-or-other.

Very true! The words "dead on" are somewhat of a misnomer.
Everything has some error if you look closely enough.

So the typical way to get a full circle out of 45 degree wedges is to
join
four wedges for the left half, join four wedges for the right half,
and joint both
halves to make the final joints fit.

I've heard of this. It's a popular technique among those who do
segmented turnings. The joints will all be tight but the circle
becomes a bit less circular. The lathe guys end up having to make the
walls of their turnings a bit thicker so that they can then turn them
round.

Another way is to temporary-
mount the items
side-to-side with the crack, run it through the table saw to open that
crack to
a straight 1/8" void, then close the joint. Kerfing was what Roy
Underhill
called it, though his technique used a handsaw...

In other words, cut both pieces at the same time. Yes, I've used this
technique (long, long ago). You pretty much want to assemble the
whole thing first. For something like a frame, where you have to
maintain equal lengths on opposite sides, you'll end up cutting
through all of the joints - gap or no.

There's a third option that you didn't mention. That is, cut the
pieces accurately enough to avoid the gap in the first place. Then
you don't have to use these or any other methods to rework the
joint(s). It takes a bit more skill and knowledge but it's much
faster and cleaner in the end. The other techniques are good for
those who are not interested in developing their machinery skills.

Ed Bennett


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