Preferred metal finishing methods - Discussion

[Jwest7788]

I've been trying my hand at metal bluing, but have not been coming up with anything too pretty. Trying to achieve this look, but need practice still.

--> Skip to 8:15 for the bluing mentioned above.

What are your preferred metal (not just steel!) finishing techniques?

 

[PeterT]

I saw that same video. The color & finish is very attractive. Unless I missed it, he doesn't really say what the material is. He treats it like tool steel, but in another part he is free-handing it & looks like brass? I've done some similar simpleton torch hardening of O1 tool steel (the same heating & oil quenching routine he shows, but without the boric acid/alcohol/wire nest to prevent scaling). But I have not done what he calls blueing. At least I have not implemented that temp because my application was for a cutting tool so needed the straw yellow color (about 450 F). According to this link, blue occurs at 550-575 F.
http://www.threeplanes.net/toolsteel.html

I have heard of people heat bluing steel like this (for cosmetics, not part of a hardening/annealing process). I've seen regular ovens used although that's probably getting to the limits they can do & maybe explains so-so results. Your kiln would be good! I seem to recall oil quench though, maybe that's intended to lock in the temp so it doesn't migrate & change color. I'm not sure what his brass shavings do - heat transfer or also related to color?

I've tried some of the ambient coating 'gun blue' spot repair kits & similar blackening dips. Kind of mixed results. Black was better, blue turned out kind of blotchy like varying coats of watercolor. I just do it on some shop tooling just to avoid rusting (although my understanding is these kits are essentially an oxide coating = rust of a different flavour). The finish out of the solution is always kind of chalky. It needs some kind of 'sealer' & this is where I'm not really sure what is best. For shop tools I figure they are going to get oily so just used light machine oil or WD40 & it seemed to hold. For decorative work, I suspect its maybe more like a chemical/paint type sealer.

These coatings aren't thick, if you scratch it you can see metal pretty quick. The better the metal finish, the better it looks. Cleanliness is super important. I found acetone or brake cleaner works best.

My experiments with aluminum coloring kits have been butt ugly. They seem to frost up particularly bad & color scratches off very easily. I think anodizing is the way to go, but I have no enthusiasm for vats of acid + regulated power supplies.

 

[Tom O]

This can probably explain the wire wrap and borax.

http://madmodder.net/index.php/topic,10858.0/topicseen.html

 

[PeterT]

I posted him a question. I'm kind of new to the Youtube/Google+ thing, hopefully it works. My search for boric acid powder turns up... roach killer!

The madmodder comment I don't quite understand. "I've used stainless steel foil - excellent for the heating but definitely affects the quench"
By 'affects' does he mean temperature issues? I haven't used the SS foil myself, but my understanding is its very common. Maybe there are different brands or techniques? I've also read about variations:
- nothing in the foil envelope but endeavour to wrap tight & keep air volume minimized
- when you cant do anything about air volume like holes in the part, adding a small piece of brown paper to burn & consume oxygen without affecting metal finish
- injecting inert gas like from a welder bottle into bag before sealing
- puncturing the bag while submerged in oil so the oil contacts the part.

I guess this quenching business is a specialty unto itself. My simpleton .25" dia O1 experiment was really uneventful in terms of scale. It came off quite easily with light brush abrasive pad & wet/dry paper & finished quite nice under tempering. I used some (new) detergentless motor oil I had laying around. I've since read that's not ideal, it has a lower flash point. Some people prefer cooking oils apparently (and then your shop smells like McDonalds fries!)

Aside from this 'heating up' business (and I guess confined to steel) I'm intrigued by this process. Seems like a bit of time involved to get the end result, but mostly simple household items & not the salt baths & nasty fumes which I understand is the 'real' way gun makers accomplish this.

 

[Tom O]

I would think that the wrapping in wire will hold the heat better on small pieces that may otherwise become multicolour the borax may help hold the heat. I appears this is used by clockmakers in various forms like this one.

http://www.garrick.co.uk/process-thermal-bluing/

 

[PeterT]

Clickspring replied his steel screws were made from EN8, which is supposedly equivalent to 1040/1045 in N-Am. And I somehow missed his first vid where he shows similar steel fastener making & blueing. This time no hardening. After machining & polishing, just heated to blue using a kind of heat transfer plate & then into what I think is oil (maybe more to lock the temp migration?). I'm sensing the high gloss surface finish plays a part in the overall color effect. Its really quite nice especially against the brass.

 

[Jwest7788]

This can probably explain the wire wrap and borax.

Slick, They actually recommend specifically iron wire, in order to bias the oxygen reaching the wire before it oxidizes the part.

 

[BradH]

RE: the blue screws, yes, the idea is to heat to colour and then quench to lock. This guy does insane work - awesome kind of insane. Very meticulous.

I have used Caswell's black oxide kit before. Don't have the gear anymore. I work in Aluminum a lot, and haven't bene finishing anything much lately. Would like to try anodizing, and also get another black oxide kit.

 

[Janger]

Anybody do any powder coating? I plan to buy harbour freights powder coat gun when I'm next in USA. $65. Nyc cnc has a good couple of videos on the process end to end. Gotta like his enthusiasm. The oven is a problem. Toaster oven is good, but not that big.

I need to finish about thirty to sixty 12"x12" steel plates so they don't rust. Spray paint is just not durable. I'm considering buying jax black but it's pricey. What else? Powder coat?

 

[PeterT]

I've only had powder coating done by a company in Calgary long time ago.
FYI, I noticed powder coat supplies at KMS the other day. Not sure about the gun. Typically if its Harbour Fright, sometimes you see the same stuff with a different sticker.
https://www.kmstools.com/search/res...in_description=&categories_id=&keyword=powder

 

[Jwest7788]

I need to finish about thirty to sixty 12"x12" steel plates so they don't rust. Spray paint is just not durable. I'm considering buying jax black but it's pricey. What else? Powder coat?

Powder coat definitely seems to be where it's at. Mind you, I've had pretty good success with sandblasting to prep steel for spray paint. Someone also told me that you can cure spray paint to be extra durable my baking it in the oven at a certain temp too, though I haven't testing this. (Apparently this process cooks away the residual solvent that doesn't evaporate well at room temp.)

In the absence of a powder coat setup, I am happy to do some sandblasting for you if you want! (We can blast the paint/rust off down the road if it ends up rusting too..)

--> I'm still planning on getting my kiln setup with a temperature control + powder coating. Lots of trips out of town for me this summer, so funds have been tight, but soon.....

JW