Joe AutoDrill wrote:
I need to glue two large pieces of granite together at the edge.

I will not need to see the bottom of either part so I want to make a
large overlapping "plate" to span the "crack" and hold the two pieces
together.
The edge is about 30" in length and I figured an 18" square "patch" or
"plate" below glued to both sides would work. The material isn't thick
enough to use lag bolts and a plate.

...Thinking either construction adhesive or Gorilla Glue.

I'll put the plate on from below and press it up using bracing. I'll
have a lot of weight on top to keep the pressure constant overnight
or longer.
I'm thinking of using an aluminum plate simply because it's easy for
me to get and easier to move around.

Any suggestions or thoughts?

how much flexing does it have to prevent? if you just want it to stay
together when it's laying on something, some ge silicone 2 would work well.
put zigzags of silicone (since it's air cured, you don't want to prevent air
movement into the middle) on the Al, press together, and leave sit without
movement for 24 hours. it's pretty good for sheer resistance, and very good
for pull apart resistance.

i use it for gluing glass to metal all the time, and the bond can be
stronger than the glass.

regards,
charlie
http://glassartists.org/ChaniArts