Doug Miller wrote:
In article m, "John" wrote:
I built an adjustable fixture that allows me to make very accurate loose
mortise and tenon joints. I have been using tenons fabricated from hardwood,
either Oak or Poplar.

Very different physical characteristics there. Much better IMHO to make the
tenons from the same wood they will be used to join, so that the tenon expands
and contracts at the same rate as the mortises.

snip

I think it would depend on what you are building. If you are building
heavy furniture or something similar, listen to all of the other
posters. If you are making something light like picture frames, then
try the hardboard. I have been using the Lee Valley hardboard biscuits
for years to make picture frames and have never had a failure.

I also have a very quick system for cutting tenon slots. I use a router
with a slot cutting blade, a router table and two fences. The main
fence is positioned so the blade is correctly positioned for the joint.
The second fence is positioned loosely on the other side of the piece
to be cut (this prevents kickback). ie so the piece being cut is
sandwiched between the two fence. The left end slot goes into the blade
from the right, the right end goes into the blade from the left. Using
this system you can accurately cut the eight slots for a picture frame
in about a minute.