On Apr 3, 5:30 pm, "paulfoel" wrote:
Sorry for being dull but whats the difference?

Does this apply to fitting dado rails ???? Please explain.....:-)

There are three occasions for scribing or mitring a joint in a board.
It depends on whether the joint occurs on a straight run, an outside
angle or an internal one. You mitre a straight run and an external
corner.

When you mitre a dado or skirting board you are creating a butting
joint that depends on the wall being perfectly square and so firm that
it will not give the slightest as the boarding is fitted.

When you mitre an outside corner the two pieces to be joined are going
to be banged together during fixing.

Doing that to an internal angle, the joint will open -it will be
forced open. Also, over time the joint will open as the material
expands and contracts. You will be very disappointed with the effect
that that produces.

With a scribed joint the two boards are again abutted but through the
complete thickness of the scribed board. Any shrinkage will seem
minimised and any gaps in the joint that appears will fill very easily
with paint or filler.

You mitre straight runs in boards because with such a mitre, any
movement will be minimal. The surfaces mitred are large and can be
nailed fairly easily.

You glue and nail them having cut the join over a stud. Since you can
fix them to the stud, movement will be almost zero.

The alternative there is to chop the board straight through at 90
degrees. If you do that, any movement in the boards will show up as a
gap in each joint.