If any one wants to flare a plate of copper i found this easy and made it out of what i had lying around.
This was for 1/2 inch pc tubes but up scale for your requirements.
I drilled a 8mm hole in annealed copper plate.
Install a m8 threaded rod ( or a long bolt)
I found a nitto air fitting and the second step on it was 1/2 inch. That on one side.
A 3/8 15mm socket on the other side a washer and a couple of nuts.
Wind away untill the second step is well in the copper and remove.
Walla.
P.s try and hold the socket square while doing the nut up. To stop distorting the plate to much.
Worked for me . Give it a go on a peice of scrap :handgestures-thumbupleft: