Sanding 304 Stainless

[erikmannie]

I am working on this project where the customer wants the stainless to be sanded to 600 grit. The material is 304 stainless.

When I bought the material, I didn’t think to buy stainless that was already polished. I just asked the steelyard for stainless, & it would appear that they provided structural SS.

It came with a mill scale on it. Here are 2 pictures of that.

 

[erikmannie]

I have some 42 grit poly strip discs, & to my horror this is what I saw after I stripped off the scale:



The first thing that I tried was a 40 grit *flap disc* on a 4-1/2” angle grinder, but that left deep scratches. I went to Harbor Freight and got some clearance 120 grit flap discs. *I was happy with that result*, but that leaves me with the problem of getting rid of the 120 grit scratches.

I tried using an orbital sander with 60 grit, 5” 8 hole sanding discs, but that didn’t do too much. One gets the impression that the stainless is *too hard to be sanded by an orbital sander*.

Adding to this, we are reminded that the stainless is being work hardened with the elevated temperatures resulting from the sanding work.

 

[rabler]

I suggest trying a woodworking belt sander, starting with 80 grit.

 

[erikmannie]

It needs to be pointed out that the 120 grit flap disk work does not produce a perfectly flat surface. I succeed in removing all of the pits and uneven surfaces on the material, but I am a human, not a surface grinder!

Since the orbital sander was practically useless, I went back to the 42 grit poly strip disc. Here is a picture of one of those after it has been loaded up with SS dust:



After using the poly strip disc (being very careful to keep it flat), I almost bring the material back to flat. Here is a picture of that result:



My only ideas at this point are to either:

(1) use 40 grit, 5” sanding discs on the orbital sander, or

(2) use 60 grit (purple) poly strip discs, but when they get loaded up with dust they become counterproductive.

Here is my weak sauce orbital sander. It is no match for the hard SS.



Any ideas? I will be offline for the next 12 hours because I have to go to work.

 

[erikmannie]

I suggest trying a woodworking belt sander, starting with 80 grit.

That is a great idea. My Dad has one of those that I can use, but at the moment I’m too broke to buy belts for it.

 

[Aukai]

Can you get it chucked up, and solid no overhang, or supported well on the mill, and face mill it? Take a minimum DOC for the inserts to work well, and ask about RPM, and feed.

 

[erikmannie]

Can you get it chucked up, and solid no overhang, or supported well on the mill, and face mill it? Take a minimum DOC for the inserts to work well, and ask about RPM, and feed.

I was thinking about that. The pieces, however, are almost 5 feet long.

 

[Lo-Fi]

Belt sander gets my vote. It'll make short work of that.

 

[Flyinfool]

I was thinking a hand held belt sander to get close.

The other thing that may work well is a flap drum sander.

 

[Liljoebrshooter]

Your using woodworking tools on metal.
Joe