bad polishing job?

schaubster

schaubster

Been Around the Block
I recently had some parts polished by a gentleman i found on craigslist. My parts were dull and a bit scratched but not horrible. When i got them back they didnt look that good to me. Unfortunately i do not have much experience with polishing so i dont know what i should expect.

They looked shiny but i could see lots of light scratch marks in them. Should i expect them to be completely smooth?

I'll post some pictures later...
 
You have to establish ahead of time what kind of polish you are going to get for what you pay. I'll show you a couple examples. This first one is fork sliders showing one before polishing, and the other after. It's not what I would call "show polish." You can still see some scratches from sanding the surface prior to polishing and some surface texture from pitting and the mediocre factory polishing.

nighthawkforks.jpg



These pictures are before/after of a GS450 stator cover. It was in rough condition. The recess for the badge was removed by grinding with 120 grit Rolllock disks in an air tool, then sanded with a palm sander. Then it was wet sanded by hand with 220, 320, 400, 600, 800 grit paper. Finally, it was polished on a 3,600 RPM buffer using an emery bar followed by a rouge bar, (different buffing wheel with different polish.)

This is what I would call a "show polish."

StatorCover1.jpg


StatorCover2.jpg


I spent quite a few hours achieving this polish. It was pretty much worse case scenario given the poor condition of the piece when I started, and the fact that I was reshaping it somewhat, so had to start with some fairly course grit to remove material.
 
Hey AlphaDog-

I decided to take on some of the polishing myself but am having trouble getting that really nice mirror shine. My process has been sanding 320, 600, and 1200 by hand. Then using an emery bar on a spiral sown cotton wheel and finally using a loose cotton wheel with a white bar.

The parts look okay but I can still see really subtle scratches. Should I be raking my loose cotton wheel?

Any suggestions are greatly appreciated!
 
I know the post isn't directed to me, but I'm bored so I'll chime in anyway...

First, 320 may be too fine of a grit as a starting point. If you have any visible scratches to start with, you may want to start lower. I usually start at 220 grit for aluminum or 120 grit for steel.

Next, the jump from 600 to 1200 is WAY too much. You'll want to hit 800 and 1000 grit along the way. Make sure all your sanding is done wet, too.

Also, emery bars (including your white) have a cutting action and so you will rarely, if ever, get a decent polish from them. You need a coloring bar like brown tripoli.

Finally, loose cotton wheels are only for the final polish such as with rouge. Use a sisal wheel or spiral sewn wheel with your emery and tripoli.

Instead of the rouge, you can also finish with a microfiber cloth and chemical polish for a really nice mirror finish.
 
Depending on how bad things are, I've been known to use a file, then start at 80 grit.
Then it's go through 120,180, 240, 320, 400, 600, emery compound on stitched mop, brown compo on stitched mop
Finally, brown compo on 'loose' mop. (no spiral stitching)
 
You've pretty much gotten your answer. If you still have scratches from the previous grit, keep working until they are gone before you go to the next finer grit.

Taking a big jump in grit like from 600 to 1200 never works. The 1200 would take forever to remove the 600 grit scratches. If the scratches that you still see are from the 600 grit, then go to 800 and work your way to 1200. If the scratches are ones that were in the piece before you started, then go back to 120 or 240 and start over.

You have to use plenty of pressure with the spiral sewn buff. There needs to be enough power in the buffer to build some heat in the piece to melt the tallow in the emery bar. I have found that if I pre-warm the piece is a 150° oven before I start, the work goes a lot faster.
 
If you could see scratches and marks in the parts then it's not a "good" polishing job, simple as that!
 
So to clarify, the black and hits bars will cut the metal. And the brown tripoli will color it? I was under the impression the white bar would color.
 
You can get it shiny with emery compound alone, use brown to get final 'colour'.
I wear mechanics gloves with knitted cotton gloves over them as parts should get hot.
If you get black build up on parts, apply MORE polish to wheel and polish it off.
If wheel is getting too 'dry' use some soft brown compo with emery (I keep a bar just for that reason)
Only need a few seconds application of polish once wheel is 'loaded'
Little and often works best
 
I really appreciate all of the advice. Polishing, like many things we do, is hard to be taught over the internet.

I was able to get a pretty good shine out of my parts. I found my problem was not enough sanding throughout the grits and I wasn't going as hard as I should have been with the emory compound. You really have to apply some pressure and the parts end up getting pretty darn hot!

I will post some before and after for your enjoyment!
 
I look forward to seeing your final result.

There are several keys to success with polishing, and it looks like you have gotten them. <G>
 
out of curiosity when you want to polish around the bolt area, I have always had issues where the wheel will start cutting into the soft alumn, do you just wedge a bolt in there? Also what is your recommendation for tiny nooks and crannies? Just a dremmel?
 
I use an 8" wheel on my bench grinder with different wheels with different compounds.
 
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