[ChrisH]

There are circular saws that can do this. I've cut 6061 plate in excess of 1" thick with one.

BUT....

1) It was at work and the circular saw was the biggest monster i've ever seen. It was very heavy too.

2) Since I got it from the tool crib, it was already set up with a blade and I have no idea what we used.

3) It was loud enough that regular ear protection was insufficient. We used earmufs over ear plugs and that was marginal.

4) It seemed to take forever. The cutting speed was quite slow

A 1/4" sheet won't be as bad but still ... I'd be looking for a really big shear. A local metal supply place might have one that can do the job. They will probably charge a cutting fee but it will be cheaper than a saw.