Re: ON topic- Flycutting ALuminium

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".

--
BottleBob
http://home.earthlink.net/~bottlbob

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Relevant Pages

  • Re: Seans "methodology"
    ... The tolerance on the 200mm cube is 2.8 microns. ... with respect to flatness and parallelism: ...
    (talk.origins)
  • Re: Seans methodology again.
    ... If the tolerance on the flatness of the block is 3 of 4 microns, ... If the tolerance on the parallelism of the block is 5 microns, ... as measured from the center is a fraction of the *total* distance - ... So these blocks do *NOT* meet your criteria. ...
    (talk.origins)