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Old 01-04-2014, 22:31   #1
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polishing stainless steel

Can anyone advise me please?
After welding and pickling, I grind with a flexible disc, then with a 240 grit emery flap wheel (the finest). Then I try to polish with stainless cutting compound on a calico wheel. I get a nice shine, but the grinding marks are still there. Obviously there is some step between the 240 grit and the calico wheel. What would it be?
Thanks.
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Old 01-04-2014, 22:49   #2
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Re: polishing stainless steel

Just about every grit you can get up to about 600. You have to go way beyond 240. You can't even really skip 1 grit, you need to go one step at a time. If you have a serious buffer set-up you can skip grades but otherwise you need to put in the time. I would not do any pickling or acid cleaning until after the buffing.
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Old 01-04-2014, 23:15   #3
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Re: polishing stainless steel

Wow! 600grit.
Sounds like specialist gear and not the sort of abrasive I will find at my local hardware store.
Thanks for your reply.
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Old 01-04-2014, 23:23   #4
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Re: polishing stainless steel

How about a buffer and jewelers rouge. Would they work on SS?

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Old 01-04-2014, 23:55   #5
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Re: polishing stainless steel

If your using a rollock disk then you can get some fine and very fine scotchbrite pads. The course pads will cut like 125 grit. Once you get the best you can with the finest then you have to polish with the right compound. Here's an excellent web site for instructions. How To Buff And Polish - Caswell Inc
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Old 02-04-2014, 00:53   #6
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Re: polishing stainless steel

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Originally Posted by Chrisc View Post
Wow! 600grit.
Sounds like specialist gear and not the sort of abrasive I will find at my local hardware store.
Thanks for your reply.
You might be pleasantly suprised. I picked up some paper just this morning from my local paint supplies place, 400, 800, 1500 and 2000 wet and dry (respraying my wife's car). There were even some grades between those (1200 was one I think), but I have found I can jump them if I am careful. I've seen most of those grades at the mainstream hardware places too.

I too would not pickle till the end of the job, at least, that was the way I was taught by the local SS fabricator.

Matt
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Old 02-04-2014, 06:06   #7
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Re: polishing stainless steel

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You might be pleasantly suprised. I picked up some paper just this morning from my local paint supplies place, 400, 800, 1500 and 2000 wet and dry (respraying my wife's car). There were even some grades between those (1200 was one I think), but I have found I can jump them if I am careful. I've seen most of those grades at the mainstream hardware places too.

I too would not pickle till the end of the job, at least, that was the way I was taught by the local SS fabricator.

Matt
There are some headlight kits for sale in the auto part stores here in the states made by 3M and others that have 4 different sanding grades. Nicely cut round disks and a soft applicator holder. Ive used them to get that yellow UV discoloration off of the lenses. Great for any clear plastic you may want to sharpen up I can say that. It gives it a brand new look. I was done and it looked like I just bought them. I believe the grades are 80, 300, then 1000 (wet) and 2000 (wet). For plastic it has a buffering polish protective coating to add as well.

The finishing 2 disk grits seem pretty tough to last a while. Almost foam like. Not paper thin like sand paper.

3M Headlight Restoration Kit part #39084. Nice little package under 20 bucks if you have a small amount to polish up.

I don't know if the steps in between grits is to steep. That's my question using paper to metal. How big of a jump in between grades is to much.

There a kit just something with it all together with a nice foam applicator pad to hold the paper. Instead of a bench grinder/buffer and the rouges.
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Old 02-04-2014, 15:57   #8
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Re: polishing stainless steel

I should have explained, I pickle my stainless work after welding and again after final finishing. Probably not necessary but I guess ignorance is one of the perils of being self-taught. My rationale for this is that I have grinding discs, flap wheels etc exclusively for stainless and another set for mild steel. My understanding is that after welding stainless the composition of the steel in the heat affected zone changes and you get surface 'rusty bits.' Sorry, don't know the correct terminology. These 'rusty bits' are neutralized or removed by acid pickling. I was thinking that if I clean up the welds without pickling first then my abrasives are going to get contaminated with 'rusty bits', which will render them unsuitable for future stainless steel work. I know that engineering firms are very hot on cross contamination between their steel and stainless workshops.
This is probably only of academic interest, but I would still be interested to know your views on this.
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Old 02-04-2014, 16:10   #9
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Re: polishing stainless steel

There might be something to that. I have made quite a bit of stainless stuff and only treated the surface after polishing. There is often a bit corrosion that shows up somewhere BUT finished welds with no grinding on them show no corrosion most of the time. So I don't know about "cross contamination" from a welded area.
I have always thought the corrosion I see on my stuff is from a poor cleaning job.
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Old 02-04-2014, 17:45   #10
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Re: polishing stainless steel

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Originally Posted by Guy View Post
Just about every grit you can get up to about 600. You have to go way beyond 240. You can't even really skip 1 grit, you need to go one step at a time. If you have a serious buffer set-up you can skip grades but otherwise you need to put in the time. I would not do any pickling or acid cleaning until after the buffing.
Guy nailed it on your first reply. You must sand all the scratches out before buffing.
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Old 02-04-2014, 18:03   #11
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Re: polishing stainless steel

I assume you are talking about just the welds and heat effected zone. Just keep in mind... everything that abrades makes scratches, the rougher stuff you start with the more you have to grind away to get rid of what you just put there. Nothing wrong with polished welds that aren't smoothed out either... if they arent messy looking anyway!
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Old 02-04-2014, 18:51   #12
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Re: polishing stainless steel

It is important to use compounds especially for stainless. Yes you have to sand to finer grits but with the correct compound I have polished 320 scratches. Sewn wheels work best with stick style compounds. Both are available from Estwood Products
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