On Sat, 19 Oct 2013 18:44:23 -0500, Ignoramus23452
wrote:

I have a 3/4" thick steel plate that is 3/4" thick.

Amazing! Simply amazing, Ig. How did you determine that? thud


It is bowed in the
middle along its length. The worst un-straightness is in the middle
and it is appx. 1/4". I would like to straighten it. How can I
realistically do it, if at all.

Is there any curvature across the 5' direction?

What is your reason for wanting it precisely flat? You -might- get
the bend out by placing 1/2" strips on each end, with the bow up, and
let the thing sag, perhaps with a bit of weight on top in the area
it's bowed. The reason it's there is probably a 3 degree Centigrade
difference between the top and bottom during rollout. (SWAG)

It would probably pull out during welding if attached to a perimeter
frame.

1/4" in ten feet (of a whole lotta metal) ain't a whole lotta
bow...unless it's for a surface plate. Does it flatten if you walk on
it? Heat or brute force might give you ripples while trying to take
out the bow.

--
It takes as much energy to wish as to plan.
--Eleanor Roosevelt