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Best Practices in Mirror Polishing Stainless

cls3277

Plastic
Joined
Jan 10, 2012
Location
Bohemia, NY
I would love to get everyone's thoughts on tips & tricks for mirror polishing stainless steel flats. Its so darn time consuming that we figured we'd love to hear what other shops do in the hopes of cutting out steps or getting a better final finish.

We do a lot of polishing on 304 Alloy Hot Rolled True Bar and flats. It seems to us that the quality has declined over the past 10 years and that we find more and more pitting as each year passes.
1) We start by grinding in a wide belt sander (timesaver) in grits from 36, 60, 120, 180, 220, 320, 400, 500 & 600. I know 36 sounds too rough, but it seems to be the only way to get the pitting out at times.
2) We then wipe down the bars and then move to a scotchbrite wheel to smooth out any lines from the abrasive.
3) Next we move to a sisal wheel with a cutting buff in a polishing lathe. Wipe part to remove excess compound.
4) Next we move to a green compound (Matchless) on a spiral bound buffing wheel. Wipe part to remove compound.
5) We finish with a loose fleece wheel (soft) with green compound (matchless). We generally get a mirror polish out of the green, without needing to move to the white/gray finish compound. Wipe part to remove compound and clean with soap and water.

Questions we have:
1) We generally use aluminum oxide abrasives. Do you think we'd see better performance with silicon carbide? 3M Trizact?
2) We've seen in some videos on youtube that some people go straight from 220 or 320 to the cut buff. What is your opinion on where you should end up grit wise before you jump to buffing?
3) How much pressure do you typically apply when buffing? Would you agree that as long as you don't feel the piece getting too hot that you are OK?
4) Is it worth paying for the 303 Cold Formed True Bar or 316 Hot Rolled True Bar as a starting point vs the 304 True Bar (that is worth the extra cost!)
5) Would anyone recommend a particularly manufacturer of wheels and compounds?
6) What are peoples thoughts on the best hand held polishing equipment - Metabo?
7) Any other tips / tricks / recommendations?

Thanks!
Chris
 
Yeah, the ceramic grit which is the same stuff as in blue seeded gel surface grinding wheels is awesome stuff, whilst still only aluminium oxide, it cuts a lot faster and really does last - self sharpen a lot better. Have never ran a time saver belt sander but it might be possible to jump a few of those grits especially as you get finer. Going to a buff too soon though and it normally shows in the finish, the reflection will have a waviness that a finer sanded finish does not. But to a degree it depends on the customers expectations.

Metabo is my go to source for power tools these days, there some of the best quality - value for money going. Yep there’s more expensive, and oftern cheaper versions but i have not had a metabo let me down yet.

Key thing about any polishing is to allow for the time it takes in the qoute. Its never ever going to be a fast process.

As to heat, i find it seams to help speed up the process.

As to true bar, we generaly tend to work a lot more from sheet to get around that problem. of-tern going laser cut parts, even when flat is a option. Some of the stainless flat is truly horrible crap. Which IMHO is pretty poor when you consider what it costs. Even with sheet, theres a noticable ugly skin unless you get prepolished sheet, whcih can sometimes still offer a good saving even at 10mm thickness’s. So long as your laser cutter grasps its to be handled as the expensive bloody delicate stuff it is.
 
Check with Klingspor for belt prices. Sandpaper for Woodworking, Metalworking, Boat, Wind, Rail, Autobody, Glass, Belts, Discs, Sheets, Rolls, Hook and Loop sanding Our company - KLINGSPOR Abrasives, Inc German company with manufacturing facilities in the US as well. I can buy their alumina zirconia (blue) belts for less than 3M's standard aluminum oxide belts, and the Klingspor belts will outlast the AlOx by 3 to 1 or more.

Klingspor's US headquarters is here in NC due to the concentration of the US furniture industry here at the time that they came to the US. Once they were on the scene, they wiped out the dominance of 3M and Norton for abrasives in that industry pretty fast because of both price and performance. Telephone #, etc on the front page of their website.
 
I am not an expert or do massive quanities of things but have a fair amount of hands on experience polishing stainless. From my experience, The slower RPM buffers are better. I used an old motor with an erbor for years with good results. It ran 1750 RPM and decided to "upgrade" to a Pedestal Baldor buffer. Bought a new one and can't get a mirror out of it without a LOT more work. It runs 3600 RPM. I basically do not use the Baldor anymore for buffing. After wearing out my original old motor I located another that runs 1750 RPM's. Great finish and same results.

Rounds are cake to polish and if the pits are gone I do go to buffer after 320 grit. If nothing else, it shows up the flaws. Flats? that's a different story. Sometimes go up to 2500 grit and use diamond compound if needed. It all depends on how picky you are. I use standard wet dry sandpaper, dry.

I'm different than most as I use only tight woven/sewn wheels for buffing. No sisal or flap wheels. I've tried just about all the compounds out there and the one that works the best for me is Eastwoods Stainless compound with normally nothing else. Yes, Eastwood, the old car tool place. Try a tube and see. Diamond compound is great as well but the cost is WAY higher.

Again, Not a claimed pro or know everything but I know what has worked well for me and the results speak for themselves.

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Wow, nice job!

By "diamond compound", do you mean White Diamond rouge, or actual diamond paste? I'm assuming the former?
 
Wow, nice job!

By "diamond compound", do you mean White Diamond rouge, or actual diamond paste? I'm assuming the former?

I mean diamond paste that comes in a syringe. I use the yellow #3 for final polish. It works really well on large flat surfaces to get rid of the hazing. If you buy from the US manufacturer I think a 5 gram tube goes for over $20.00. There is cheaper stuff online but have no experience with them. I got a big box at an auction and lucked out as no one new it was in there.
 
If your after diamond compound, don't discredit the indian sources of it on ebay. Due to the amount of stone working done out there there prices and quality are both bloody good!

As for flat surfaces, a DA or orbital sander works a treat, but is slower than a belt for stock removal - pit removal. I also find it helpful if after a truly flat polished surface to use the half sheet orbital sander with a pice of high cotton content card - artist paper and polishing compound. Leaves a very flat surface and if using a heavy card on a hard foam backing no chance of rounding any corners.
 








 
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