If you can live with it, I would take Karl's solution. I say live with it
as you will need to square up the fence every session that you use it. May
be not a big deal. Back in the bad old days, my first "powered" miter box
had a cast iron fence with milled face. When it worked itself out of squar
e, I took the fence off and filed out the inside of the mounting hole (with
a rat tail file) on the fence enough to bring the fence back into square.
If I recall, the machine bolt holding the fence in place about 1/4". I dri
lled out the holes to a larger size and put large washers with split lock w
ashers on both sides and tightened it up. It worked well.
Now, I would probably go online and look for a fence.
In no way, ever, would cut down a piece of METAL on my jointer. You can cu
t aluminum on your miter saw as you have a large fence and a relatively sma
ll cut surface that is mechanically pushed against a backstop. Hand holdin
g a piece of metal by hand, making a 4" wide cut on a metal of >>unknown ha
rdness<< is just nuts. Or worse. Extra sharp blades could easily grab the
metal ruin the fence or rip it out of your hands. Duller blades could pro
bably cause enough chatter to ruin the face of the fence.
A 4" wide grab from a sharp bladed fast moving machinery sure sounds exciti
ng to me. There is no way you can "carefully" cut metal using "small cuts"
and all that other business. Dangerous isn't mitigated very much by spend
ing more time doing a dumb thing more slowly.
Anyone actually try cutting the aluminum fence this on their own jointer?
Love to see a pic...