It must all be in the bits. In a fit of naive foolishness about twenty
years ago, I placed a router, its bit spinning at 25K RPM against some
..062 aluminum sheet, I only needed to shave off a few thou -- BAM!

The bit was trashed, the aluminum was trashed, and by the grace of God
no blood flowed. I vowed then and there to never try anything involving
hand-held routers and aluminum again.


Ed Huntress wrote:

I don't advocate this, and don't tell anyone I recommended it in any way,
shape, or form, but...

I had a similar problem about 20 years ago, about ten times deeper than
yours, and I got away with using a single-edge carbide bit (1/2") in my
router. The aluminum was 2024-T4. I set up a very solid and unnecessarily
complicated jig, made of birch plywood and with lots of C-clamps, to make
sure it was all rigid and wouldn't slip. Through trial-and-error I got to
within a couple of thou and then finished it off with a homemade scraper.

Disclaimer: But I think it's all a bad idea. I advise against it...

--
Ed Huntress