# How To Put A Satin Finish On New Large Dials?



## woodchucker (Jul 14, 2016)

I am making large dials for my southbend 9a. I am going to mark 200 marks, and do a direct reading dial, what I don't know is how to get a satin finish on aluminum. I was thinking of glass beading them. I don't think scotchbrite will give me the satin look. I'll be testing on a scrap dial, but looking for a jump start from  someone who has done it.

Thanks.


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## dlane (Jul 14, 2016)

Glass bead first -mabey clear powder coat after


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## MozamPete (Jul 15, 2016)

I put aluminium in a caustic soda (lye) solution - like you would do when preparing the part for anodising. The caustic soda will etch the aluminium surface leaving a matt finish. The caustic soda reacts with the aluminium so you need to watch it and not leave it in too long.

Have a look at the bottom of http://www.hobby-machinist.com/threads/brushed-finish-on-aluminum.38572/#post-331493 for an example.


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## TOOLMASTER (Jul 15, 2016)

sand it, blast it, brush it,, throw it in the dishwasher


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## RJSakowski (Jul 15, 2016)

MozamPete said:


> I put aluminium in a caustic soda (lye) solution - like you would do when preparing the part for anodising. The caustic soda will etch the aluminium surface leaving a matt finish. The caustic soda reacts with the aluminium so you need to watch it and not leave it in too long.
> 
> Have a look at the bottom of http://www.hobby-machinist.com/threads/brushed-finish-on-aluminum.38572/#post-331493 for an example.


+1 on the caustic, aka soda lye, sodium hydroxide.  

Make up about a 10% solution by weight, adding pellets slowly to water, not the other way around.  The solution dissolves flesh!  Wear personal protective gear; eye protection, or better yet, face shield, and rubber or nitrile gloves. Rinse any splashes or spills immediately.  It is also a good idea to wear old clothes, preferrably cotton or synthetic.  It eats wool.

After the parts are etched, rinsed, and dried, I like to spray with a clear acrylic spray like automotive top coat.  It prevents oil or grease from discoloring the finish.  But that's a personal preference.


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## woodchucker (Jul 15, 2016)

dlane said:


> Glass bead first -mabey clear powder coat after





MozamPete said:


> I put aluminium in a caustic soda (lye) solution - like you would do when preparing the part for anodising. The caustic soda will etch the aluminium surface leaving a matt finish. The caustic soda reacts with the aluminium so you need to watch it and not leave it in too long.
> 
> Have a look at the bottom of http://www.hobby-machinist.com/threads/brushed-finish-on-aluminum.38572/#post-331493 for an example.



I like that, the finish is exactly what I am looking for. I probably will leave the hole for the shaft rough, and ream after then to get a smooth finish on the hole.
Now to figure out how to topcoat protect from staining w/o losing that look.   Was thinking satin ruler, and your solution looks like a satin ruler.


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## Bradrock (Jul 15, 2016)

What is your setup for scribing the lines? Is your project already posted here?  I'd like large dials for my SB 405 9"er

Thanks, Brad


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## woodchucker (Jul 15, 2016)

I'll take pics. Still working on building the tooling right now. Maybe some video.


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## MozamPete (Jul 16, 2016)

woochucker said:


> I like that, the finish is exactly what I am looking for. I probably will leave the hole for the shaft rough, and ream after then to get a smooth finish on the hole.



I wouldn't think that was necessary - I don't believe you are dissolving enough of the aluminium to change the tolerance on the fit, I think it is almost a microscopic etching to get the dull finish  (although I will admit I have never mic'ed a piece before and after to check, and it you left it in looooooong enough you would dissolve the aluminum).  You will know it's working as it is quite a active reaction - lots of bubbling.

Just keep taking it out to checking and pop it back in for a bit longer it you want.  Keep the parts hanging or at least moving around frequently so you get an even attack on all surfaces and ideally rinse them, dry them and spray them with clear lacquer before you touch them (the etched surface is great for lacquer or paint to key into so ideally spray them before you handle the piece and get oils back on it).

I've had good results on all purchased aluminum stock I've used so I don't think the grade matters - but experiment with a sample of whatever you are using.  I did have a disaster trying it on some home cast aluminium I had machined - well it resulted in a very different finish anyway.
http://www.hobby-machinist.com/threads/another-igaging-touchdro-install.39060/#post-338478


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## RJSakowski (Jul 16, 2016)

MozamPete said:


> I've had good results on all purchased aluminum stock I've used so I don't think the grade matters - but experiment with a sample of whatever you are using.  I did have a disaster trying it on some home cast aluminium I had machined - well it resulted in a very different finish anyway.
> http://www.hobby-machinist.com/threads/another-igaging-touchdro-install.39060/#post-338478


It has been my experience that home cast aluminum tends to be porous.  Controlling the porosity can be difficult in a home foundry.  Hot aluminum tends to react with water to form hydrogen gas and hydrogen is fairly soluble in molten aluminum.  It comes out of solution when the aluminum solidifies forming small bubbles.  When a casting is machined, the pores are exposed, creating a surface that is hard to finish.


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## Tony Wells (Jul 16, 2016)

The caustic etching should be preceded with a thorough washing to prevent any hand oils or contamination. The lye will of course, dissolve any oils, but that delays the actual etch time start. Rinse well, handle with non powder coated surgical gloves. Post etch, rinse well, and neutralize with baking soda solution and rinse well again. Warm air dry and clear coat immediately.

If you intend to fill the engraving, use something like a Lacquer-Stik. Brownell's has only one color listed, but there are numerous colors available. The etched surface will allow the filler to adhere well, but if you use lacquer, make sure whatever you overcoat with won't lift it. Like no clear lacquer over a Lacquer-Stik. Enamel uses a much cooler solvent carrier and won't generally dissolve the lacquer.

http://www.markal.com/solid-paint-markers/lacquer-stik/


http://www.engraverssolutions.com/PDFs/tips&tricks-color_filling.pdf


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## MozamPete (Jul 18, 2016)

Tony Wells said:


> neutralize with baking soda solution and rinse well again.



But isn't caustic soda already alkaline? 
Surely rinsing in Baking Soda is to neutralize acid and wouldn't have any better effect than rinsing in water at neutralizing caustic.


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## Tony Wells (Jul 18, 2016)

You're right. I was thinking upside down on pH. Baking soda is about 9, so yes, it's still basic. Best bet would be to rinse with copious amounts of water, then rinse with weak acetic acid (vinegar), then more water, preferably distilled or deionized.

Sorry about that. Funny how a few years away from doing something even every day things slip from the mind.


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## Groundhog (Jul 18, 2016)

I make emblems for hot rods and other things. When finishing aluminum to a satin finish I use a random orbital sander with either 3000 or 5000 grit paper. That leaves a very nice satin finish. For a more burnished finish I use coarser sand paper (1000 to 2500 grit) and an concentric orbital sander for swirls or a sanding block for a horizontal (or vertical) finish. I usually powder coat with a satin clear to keep the aluminum from oxidizing but that is not necessary for the finish (don't use gloss clear!)


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## woodchucker (Jul 25, 2016)

Bradrock said:


> What is your setup for scribing the lines? Is your project already posted here?  I'd like large dials for my SB 405 9"er
> 
> Thanks, Brad


Brad, I took videos, but haven't edited them yet. I suck on video. Here's some pics of the setup. Still have to use the lye. Will test before I do, to make sure my lines are still visible.   http://imgur.com/a/bpq3M

BTW see Mr Pete 222 on youtube for a great video on how to make this.


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## woodchucker (Jul 27, 2016)

my results of using lye, were mixed, my test piece had promise. It didn't remove the paint on the markings. but I had a lot of sludge and mottled appearance that came off with a good wiping.
My dial the paint came off, the finish was mottled.. I had washed the pieces before I started. I was not looking for a heavy satin look. I got to the goal, but didn't appreciate the mottled appearance. I picked up crystal drano as my source of lye.  Anyone care to comment on the mottled look?  They looked like dark spots, similar to a winshield that hasn't been cleaned after a rain.


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## Tony Wells (Jul 27, 2016)

The type of aluminum can affect the consistency, as can the temperature of the etching solution. Don't suppose you have a magnetic stir plate? Moving the solution will help. And the part must be absolutely clean.

Make sure the lye you are using is 100%. No inert ingredients. Cooler solution will slow down the reaction and afford more control and give you time to remove the piece and give it a good stir. That may help too. If you suspend the part in the solution, best to use a non-reactive material. SS wire, Nylon or Polyester fishing line.....something like that. If you can't keep the solution moving, keep the part moving. If you have a fairly strong solution, this action may only take a minute or two.


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## woodchucker (Jul 28, 2016)

so the Drano may have been the probem, I kept the solution moving regularly, by swirling it about. I used cold water, but the whole thing got hot over time. The aluminum was hot too.   6061 Al is what I was using.  I had cleaned the part first using soap and water, because I had already painted it, I could not acetone drop it again.

I'll have to order lye online, as I can't find anything but Drano.


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## MozamPete (Jul 30, 2016)

Drain cleaners tend to have Aluminium powder (and other things) in them already to react with the caustic soda when water is added. The vigorous reaction helps to remove the drain blockage.
You want to use straight caustic soda.


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## Tony Wells (Jul 30, 2016)

Red Devil Lye is 100%, with no Aluminum, and WallyWorld advertises Rooto as such

http://www.walmart.com/ip/100-Lye-Drain-Opener/38691438


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