brushed aluminum finish, how to?

[power]

We'll see if this post works. I have timesaved aluminum parts before but the results do vary with some parts having flaws such as slight rolling of the edges, etc. What other methods are there to "grain" the parts with the same if not better results. There must be a way

 

[Sch3mat1c]

I think it's done with a belt sander.

Tim

 

[Pbassred]

I once did a "machined" finish (circles) using a 1" wire brush atachment with an electric drill. You need to watch it on brass because it tarnishes so quickly. You could get the brushed finish with the edge of a wire brush disk.

 

[Coulomb]

You could use a belt sander but if you wander at all it ruins the effect. I found if you make a jig with some 1x1 screwed to a panel of 3/4" board that traps your sanding block from wandering left or right, you can then pass the sand paper back an forth over your face plate to get the nice finish.

Anthony

 

[Peter Daniel]

I'm using 6" belt sander with 100 or 120 grid belts. Depending on the tension on a belt you will get more or less of the rolling of the edges. To wet the surface I'm using Varsol (or paint thinner) with very good results.

If you really want to avoid rolling of edges, the best approach would be making part longer and after sanding, trimming it off.

It's hard to get perfectly uniform finish on a belt, so after that I'm using Sotch Brite pads to further smooth the surface. Depending how long you do that, the finish can become really nice and pro looking.

Recently I started using Alodine at home and I'm getting fast and satisfying results, without having to wait 2 weeks for anodizing house to finish my panels.

I recently acquired Mark Levinson top cover door from their top of the line CD transport, and to my surprise their sanding job (done on a belt) was inferior to mine

 

[power]

the problem i see by doing the sanding manually with a belt sander is that if your workpiece is wider than the belt it would be difficult no to leave steps. Scotch brite may take it out but if you are doing several parts consistancy comes into play.

I have seen another process where acid is used to create the brushed finish. Very professional but also very expensive.

Beautiful looking work Peter!

 

[BrianGT]

I recently found that using a random orbit palm sander, with 80, 100, then 220 grit paper works great for taking out scratches in aluminum panels, then using a kitchen type brillo pad works great to give it that brushed look. I like using the kind with the sponge attached, as it allows for a more uniform pressure on the metal. The brillo pad easily takes up the scratches left from the 220 grit paper on the sander. I got the advice on the brillo pads from the machine shop guy here at school. That is what they use before anodizing aluminum panels. Before I used synthetic steel wool, but had problems with a non-uniform finish.

--
Brian

 

[purplepeople]

Try dragging a coarse hand-file sideways in the direction of the brushing. Takes more time than power tools, but you have much more control. I like to use a palm sander to get most of the surface, then drag my file to finish the "brushed" effect. A sanding block can work, but the softness of the block can really make for uneven corner radii.

ensen.

 

[Peter Daniel]

You can make a block out of soft wood, like cedar.

I use belt sander as it is faster and deep scratches are easily removed. But I've herd from some memvers that using coarse scotch brite type pads works very well too.

Professional finishers use this type of wheel and as far as I know it's done manually. This leaves short lines (different than from belt sander).

We had Amp-1 finished this way, but I still wasn't much satisfied with the quality of a job. After first inspection 30% had to be redone.

 

[jewilson]

If youy don't have the tools

You can check you one of your local machine shops. The have large belt and drumb sanders, up to 36" wide. Just tell them you want a brushed finish using either 120 or 150 grit. Besure to tell them which way you want the grain runing.

 

[cowanrg]

for home use, ive been using a bench sander, then a hand sander (wooden block with paper attached), then finishing it off with scotch pads.

its slow going, but has predictable results. its pretty fool proof. the face plates on my avatar are taking around 1.5 hours per fin. because of the perfection of the machining work, we have to get the finish perfect too. you could easily get this done in an hour or less if you werent trying to get it perfect.

 

[Peter Daniel]

Actually the grain direction is dictated by the material. You could go across the natural grain of aluminum, but the results are always better if you go along. I tried few times doing it across.

 

[sam9]

I've used the hand method - a sanding block wider than the workpiece starting with moderately coarse wet&dry (use wet) paper until the scratches and dings are gone, then progressively finer paper until it looks right. Tricks: find a way to hold the workpiece adsolutly immobile B: stand, sit ot squat in a postion that helps you make complete strokes from one end to the other and as straight as possible C: count the strokes after fixed number reverse the workpiece and make the same number from the opposite direction (otherwise one end will tend to look different from the other) D: lots of soapy water E: wear old clothes and don't be afraid of making a mess.

I have not bothered with alodine yet - I'll try that on the next project

 

[jewilson]

Aluminium Oxide sand paper is the best for metal it will not wear out as fast. You can use granet or other woodworking sand paper they just don't last as long. If you have a Drum sander Aluminium Oxide is a must.

 

[Jason_N]

Changing the subject slightly...

So what can you do with the aluminum after you are finished brushing? I would like something that is clear (or close to it) and that I can do myself. What are the options?

Thanks,
Jason

 

[Peter Daniel]

Alodine. If you want to have it close to clear, use very light solution and brush any excess after. The pic I posted previously shows the alodined piece. You can also use some protective spray, but this will always look artificial.

 

[jewilson]

You can spray it with a polyurethane or Lacquer it has to be clean of all oils. Don't get you finger on it. If you spray it, the aluminum will lose some of it ability to conduct heat, so don't spray the heat sinks. Anodizing is cheap and doing Alodining is cheaper, call around and anodizing can be done in many colors .

 

[sam9]

Alodine questions?

Anyone know a good source for the solution?

Can anyone suggest a URL with instructions for applying it?

I did a Google search and got a huge listing that I haven't had time to sort out so if anyone can point to some sources they can recomend from their own experierce . . . .

 

[Peter Daniel]

http://www.airtechcoatings.com/cgi-local/shopper.cgi?category=PRIM&search=action

Buy the smallest amount in powder form. When making solution Use quater or less of what they recommend (when mixing) as the original receipe makes the liquid too strong.

Don't buy aluminum prep (or any cleaner) as it doesn't work well and you don't need it.

When doing actual alodining, clean the parts directly before dipping (with scotch brite). Don't dip it for more than few seconds, as the color becomes too strong and you might not like it. Extent time for required appearance. If finish is too strong or uneven, additional scotch brite brushing (after alodine) fix the problem.

Check also this older thread for more suppliers http://www.diyaudio.com/forums/showthread.php?s=&threadid=3982&highlight=

 

[sam9]

Thanks much. I'll bookmark those for my next project.