Re: ON topic- Flycutting ALuminium


"BottleBob" <bottlbob@xxxxxxxxxxxxx> wrote in message
news:13pqjaag3v398a1@xxxxxxxxxxxxxxxxxxxxx
Jerry wrote:

Funny topic.
Tomorrow I will be working on aluminium plate 30" X 16" X 0.625" thick
with
tolerance of 0.001" flatness an parallelism and I think I will end up
using
a fly cutter as from my experience nothing else will take a finish cut
without vibrating.

Jerry:

I think you'll frustratingly disappointed.

If it were me (and with that flatness tolerance), I'd not touch the
flat surfaces, but I'd rough out your perimeter, all your features &
large holes, then send it out to be blanchard ground - then when you get
it back, finish your perimeter, features, and holes.

The thing about 6061 is it has a "skin" under stress. When you relieve
that stress by removing material on one side, the part bows. Sometimes
you can removed a similar amount of material off the other side and get
lucky and have it bow back to being relatively flat. But a flatness of
.001, unrestrained? Even a blanchard grinder is going to have trouble
with that one across 30".


Bob back in the day we ran 30in and up flycutters made in house aluminum
body with lightening holes at Certified Aerospace...prepping for wing tank,
bulkhead fittings etc on the converted planers, vacuum hold downs...and
routinely held +/- 002 on 7075 pieces appx 30in x 6ft long and 1in thick
with no problem.

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