Milling a plate to be flat

Dynahoe Dave

Dynahoe Dave

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I have a piece of aluminum plate, about 8.5" square, .250" thick. It's not flat- is it possible to mill the face / faces to get it flat?
How would this best be done? I have a J-head Bridgeport mill.

The main thing I'm trying to get is how to clamp it - but the common way, obviously, the clamps get in the way...
 
What about putting it in a vise? You can usually put the jaw of the moving side on the 'back', which increases your clamping area, and gives you the top of the vise as a spot to put it on.

From there, a flycutter or a face mill, depending on how many passes you want to take.
 
Hopefully this 'toe clamp' search on YouTube will pre-populate. Otherwise just type it in.

toe clamps - YouTube

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benmychree said:
There may be so many stresses in a piece like that that you never will be able to get it truly flat.
Click to expand...

Agree with that . I would think a vacuum chuck and shims would be the way to go , but you'll also be introducing more stress into the plate when cutting . Stress relieving would help , but truly flat would probably be impossible .
 
I don't know how flat it needs to be, but your best bet is to lap it on a flat surface.
 
This is a tuff nut but standoffs on the back of the piece will help when clamping it. If the back side is not flat the piece will bend when you clamp it then obviously the front side won't be flat when you machine it.
 
Something like these go directly in t slots on table. They work great.
C807A20D-E2D2-4020-BDB6-D4D0DE4DD07B.png
 
How you clamp it has a large effect on your ability to get it flat. Edge clamps that touch above the neutral axis will tend to bow the metal down. Those that touch the work below the neutral axis will tend to bow it up. Any locked in stress, as from rolling, will cause the metal to move whenever you cut it. If you need flat plate buy Mic6
 
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