Reasonable Flatness Tolerance on 235x135x2.5mm Stainless Plate

Zibraz · Jul 28, 2021

I am doing a project where I need the a stainless plate. There are runners fix to the plate where a block slides over the runners.

We have been getting plates in which aren't flat which are causing issues with our runners and alignment. I was going to put a flatness tolerance of 0.5 but i'm not sure if this is practical (I suspect it is, but I can't find any sources to confirm this).

Is a 0.5 flatness tolerance over the length and width reasonable for fabrication shops to hold the plate to?

Scruffy887 · Jul 28, 2021

I would expect a bit of twist if this is a sheared plate. Is there twist or bow? Laser cut or water jet should produce a flatter piece. If you can learn how to flatten them yourself you will be much happier.

Zibraz · Jul 28, 2021

The part is laser cut. Apparently there is a bow in the centre of 1.5mm. I don't think the bow is an issue because the panel is bolted into place, but someone else is worried about alignment of certain parts.

Conrad Hoffman · Jul 28, 2021

One could grind it or fly cut it, but being thin it will still likely have a bit of warp. Can you just shim the runners to put them in the same plane?

memphisjed · Jul 28, 2021

Stainless warps when you look at it. If you have thermal holes cut in it I can see that much warp with a laser. If it is just a blank rectangle 1 mm sounds a little rough. I do not know if it is common size but can you get 235 / 135 x 2.5 flat bar that you can have saw cut? Flat bar will bow but not dish- easy to straighten.

Bondo · Jul 29, 2021

Due to the pandemic, I have been getting more sheets of stainless with more stress inside them. So the are perfectly flat at 4' x 10' but when I shear it to 3' x 7' it has a large bow to it.

If your issue is heat related from the laser cutting, then you can find a water jet to stop that, but it's a good chance it is from general stress inside the material itself.

Sent from my SM-G960U using Tapatalk

rcoope · Aug 2, 2021

+1 on waterjet rather than laser for minimizing stress. We once made 100mm wide "combs" with eight tines going down around 15mm where the other side of the comb was flat. Laser cutting made the 16Ga stainless "smile" i.e. warp upwards to make the flat edge concave, presumably due to the differing lengths of the two sides. Anyway, the stresses in your situation here are a bit different but if you start with flat stock the waterjet should give you a flat piece.

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Reasonable Flatness Tolerance on 235x135x2.5mm Stainless Plate

Zibraz

Plastic

Scruffy887

Titanium

Zibraz

Plastic

Conrad Hoffman

Diamond

memphisjed

Titanium

Bondo

Hot Rolled

rcoope

Stainless

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