TheSamba.com :: View topic - Polishing Aluminum to Show Quality.. How?

Sun Oct 10, 2010 9:47 am

Not sure if this in the correct section maybe but...

As some may seen recently I am kinda headlong into my 57 project... and while I am in this process I thought I would ask a question if there is anyone here well practiced in polishing old aluminum up. Or if you just figured out a way to do it or the best practice ... or thats just as shiny as it gets...

I have somewhat done it in the past on a few small tiny pieces just by starting from a general strip with 1200 or 600 grit light sand (ocasionally fine steel wool as well for that matter) and then just lowering the polishing grits down with few different felt pads with different compounds on them but have never gotten to any thing that I would classify as a show quality high polish, it always seems to be a bit dull in the end... brighter & clean? yes... But just not as shiny as I have seen others here can seem to get on some of there pieces and parts. For me I am almost to the point where I will need to polish up all of my rag rails and related pieces to our '57.

Does any one have a general practice and the compounds you use?

Before and after or even better, process pics, would be greatly appreciated...

Gene

Sun Oct 10, 2010 10:20 am

Not really a how-to but here's a thread with some information:
http://www.thesamba.com/vw/forum/viewtopic.php?t=210559

Sun Oct 10, 2010 5:23 pm

well, i once had to polish an entire ww2 sea plane to chrome finish.
(despite my warnings of hard water marks the first time they landed.. :? )

like all sanding, polishing requires removing scratches one layer at a time.
i started as far as 400 grit with some of the bad pieces. then worked up thru grits to 2000. then finished with standard buffing compounds (3m)
and finally finished with chrome polish. (generic from the auto shop)
however the part that makes the difference between cloudy and chrome, is taking the time on each grit layer. if you finish and its still cloudy you must go back a few layers. lots of time is involved however.
about 2-3 hours per 12" by 12" square.

if you have any more questions, let me know.
:D

Mon Oct 11, 2010 4:53 am

I have pics of this process http://photobucket.com/PPW
start with pic

# 944

and fin at 960

Mon Oct 11, 2010 5:47 am

deaner wrote: well, i once had to polish an entire ww2 sea plane to chrome finish.

'Off Topic': Photos :?: ;)

Mon Oct 11, 2010 9:20 am

let me figure out how to post a photo! :shock:

Mon Oct 11, 2010 9:34 am

[img]http://www.airliners.net/photo/Republic-RC-3-Seabee/0954309/M/

this is the one i went off of. a quick search of the n numbers brought nothing of my actual project so im assuming its still in restoration.

Mon Oct 11, 2010 9:38 am

Fixed it for you :wink:

Mon Oct 11, 2010 11:32 am

thanks! thats what i was going for...gotta be smarter than the computer eh? :D

Mon Oct 11, 2010 3:06 pm

Here's my method for polishing aluminum.

If its a cast part that hasn't been previously smoothed/polished, I'll use a grinder with various sanding drums and flap wheels to smooth the part. Then use 120-180 grit with a 3M Wetordry sponge pad to get the part "leveled", kinda like block sanding body filler or primer. You don't want the reflection to be distorted.

If the part has already been polished but is dull/damaged, figure out an appropriate grit to remove the imperfections without creating excessively deep scratches.

Once the part is leveled, then begin smoothing the finish by using progressively finer grit sand paper. I like 3M wetordry paper, or even better Nikken/Meguires' Unigrit paper. Add a little dish detergent to your water to lube the sandpaper and keep it from clogging as easily. If using a water bucket for your wetsanding, wash out the bucket and get fresh water whenever you work up to the next finer grit.

If working up from 220 grit or rougher, I like to cover the part with a guide coat to make sure I've sanded out all of the previous step's sanding scratches. Sharpie markers and Dykem works well.

Once all the rough grit sanding is done, start working up to finer grit paper, making sure to get all of the previous step's sanding scratches out or they'll show up later on. Each time you change to a finer grit, also change the direction you are sanding. For example, sand the part top to bottom with 220 grit until all you see are sanding scratches that go from top to bottom. When you move up to 320, sand from side to side until all the top to bottom sanding scratches are gone. This is how you will know that all of the rougher sanding scratches are gone.

Work up through these grits, cleaning the part between steps. You don't want leftover sanding residue that has rougher grit in it than the sandpaper you've moved up to; you'll never get all the rougher grit scratches out without cleaning the part thoroughly.

120-180
220
320
500
800
1000
1500

Once I work up to 1500 grit, I've got a 3" mini D/A sander/buffer that I use with Mirka Abralon wet sanding pads in 2000 and 4000 grit.

After all the sanding is done I use Wenol Metal Polish in the red tube and it comes out looking like chrome.

The biggest mistake people make when trying to polish is getting in a hurry and skipping steps. Polishing is just like bodywork/paint prep; you have to level and smooth the part before you can successfully make it shiny. Skip those steps and you'll have a very distorted reflection and not much of a shine.

A couple of examples of items polished using this method.

Crankshaft rod throws and counterweight edges. Steel, not aluminum but it's the same process:

Aluminum velocity stacks:

Mon Oct 11, 2010 6:37 pm

Astronaut, Nice work! Where did you get that 3 inch DA from?

Tue Oct 12, 2010 5:35 am

artie325 wrote: Astronaut, Nice work! Where did you get that 3 inch DA from?

The DA/buffer came from Griot's Garage. They also sell an electric version. It's made for polishing swirl marks out of paint but works great for wetsanding too.

Pneumatic version with variable speed control and aimable exhaust:

http://www.griotsgarage.com/product/car+care/car+p...orbital.do

Electric version, also with variable speed control:

http://www.griotsgarage.com/product/car+care/car+p...orbital.do

They also sell the best car care products available!

Tue Oct 12, 2010 1:23 pm

Thanks! That is definitely going to be the next tool in my collection. I might get the electric version so I can rebuff my wheels over the winter in my basement.

Tue Oct 12, 2010 2:15 pm

Another tip, this applies to bodywork and color sanding/buffing paint but the principle is the same for polishing metal.

When starting the rough bodywork- after the metal straightening is finished, use rougher grip paper to level the surface. Finer grit paper will just smooth the surface, not level it. You'll end up with a panel that is smooth and shiny but also distorted with ripples and waves, even if a sanding block was used.

Alot of guys block sand high-build primer starting with ~320 grit. This works to get the primer smooth, but doesn't do much to level the surface. I like to start with 80 and work up to 150-180 before going to the next round of block sanding. The rough paper on a flat block will easily shape the primer down flat, removing ripples and waves. Then using a guide coat to make sure the rough paper's scratches are gone, you can start to smooth the surface in preparation for paint.

When color sanding orange peel from paint, start off with 1000 grit to level the surface and then work up to ~3000 grit to ready the paint for buffing. You must have at least 3-4 coats of paint/clear to do this. Use a squeegee and check your progress often; stop sanding with 1000 grit as soon as the surface is leveled and all orange peel is gone. I like using Nikken/Meguires UniGrit paper to make sure the scratch left by the paper is a uniform size; some brands of sand paper don't have a uniform grit size and can leave deeper scratches that are hard to buff out.

Example of paint cut/buffed this way. Polishing aluminum using these principles produces the same results.

This is shot of the reflection of our pegboard storage wall. Notice that there is no distortion in the reflection; all the holes of the pegboard are lined up straight.

Painted panel on left (you can faintly see the outline- left of center in the pic), actual shop van in background on right:

If bodywork is 90% of a paint job; leveling and smoothing (removing all of the sanding scratches) is also 90% of a great polishing job.

Sun Oct 24, 2010 8:03 pm

I have a question for the polisher guys here...
I have this set of rims, the spoke turns in very deeply to meet the rim lip.

where the spoke meets the lip there is only about 1/2" to 5/8" of space for sandpaper and fingers to sand the deepest part of the dish of the lip.

I have a setup to spin them on a drill press while I sand them.

so far, to sand them I have wrapped sandpaper on a bondo spreader to reach the deep part of the dish. but it's a pain and it's not possible to sand cross grain on the next grit to be sure you got all the previous grit line out.

I've looked for a tool like a cartridge roll but they don't come in fine grits, just 180 grit or so. I've also tried wrapping finer wet dry on a wood dowel held in a drill motor...that doesn't seem to work too well either.

so I just sanded them like I said with wet dry on a bondo spreader (it's flexible and conforms to the inner radius of the dish)
but not using the cross grain sanding when stepping down to finer grits, it's really hard to tell if all previous harsher lines are gone.

then I buffed in this same setup with a rag and buffing compound (black emery) the compound wouldn't melt like it usually does due to heat friction so I used WD-40 to sorta melt the compound into the rag. it worked ok but there is still a ton of lines in the lips.

I'd like to re sand them, but not real sure what kinda tool to get at that deep lip since it's so narrow at the spoke.

anyone got any clues ??? :D
right now they look like a real shiny brushed aluminum.
I'm sure they'd look swell @ 35 MPH. but like I said I'd like to get them nicer if I can without paying a polishing shop.

the lip/dish is about 2 5/8" deep.

Mon Oct 25, 2010 9:08 am

Crankey wrote:
so far, to sand them I have wrapped sandpaper on a bondo spreader to reach the deep part of the dish. but it's a pain and it's not possible to sand cross grain on the next grit to be sure you got all the previous grit line out.

I've looked for a tool like a cartridge roll but they don't come in fine grits, just 180 grit or so. I've also tried wrapping finer wet dry on a wood dowel held in a drill motor...that doesn't seem to work too well either.

so I just sanded them like I said with wet dry on a bondo spreader (it's flexible and conforms to the inner radius of the dish)
but not using the cross grain sanding when stepping down to finer grits, it's really hard to tell if all previous harsher lines are gone.

then I buffed in this same setup with a rag and buffing compound (black emery) the compound wouldn't melt like it usually does due to heat friction so I used WD-40 to sorta melt the compound into the rag. it worked ok but there is still a ton of lines in the lips.

Use dykem between grits and sand til all the dykem is gone. Once you get up to about 1000 grit the dykem may start clogging the sandpaper. If you go up to ~2500 you won't need to use compound to polish them up, just use a metal polish like Wenol or Autosol. As far as getting down to the bottom of the lip, try gluing two paint paddles together and glue a layer of dense 1/16" foam rubber onto the stick. The foam will help the sandpaper conform to the shape of the lip.

Mon Oct 25, 2010 10:30 am

once you sand it as best you can, try neverdull metal polish.
about 6 bucks. its got a cotton candy texture and works well wrapped around something like a drill tip. the good thing about it is you can add as much as you need to get into tight places and try different tools to apply.
hope that helps

Mon Oct 25, 2010 11:40 am

deaner wrote: once you sand it as best you can, try neverdull metal polish.
about 6 bucks. its got a cotton candy texture and works well wrapped around something like a drill tip. the good thing about it is you can add as much as you need to get into tight places and try different tools to apply.
hope that helps

I've tried Nevr-Dull and have never been able to achive the results that Wenol produces. It does clean and remove oxidation but doesn't really polish. Nevr-Dull doesn't seem to have any abrasives in it like Wenol does so it doesn't polish out fine wetsanding scratches very well. Also, the wadding is too rough and leaves fine scratches behind. Maybe they should call it Nevr-Bright :D

Mon Oct 25, 2010 12:34 pm

My "last step" was flitz. But L'll have another go with the dykem.
Thanks.

Mon Oct 25, 2010 5:36 pm

theastronaut wrote:
Crankshaft rod throws and counterweight edges. Steel, not aluminum but it's the same process:

That looks awesome 8)