How does one blacken bolts & nuts?

[PineRidge]

Need to blacken bolts and nuts for a lathe that I am presently working on. I would rather use chemicals to achieve the required finish rather than paint.

Have heard of using phosphoric acid but was not given any detailed instructions on how to use the acid.

Another remedy was placing parts in a bath of used diesel motor oil and cooking it on the gas grill to provide a dark, rust preventative coating. They went on to say that it is important to use used motor oil from a diesel engine for the sulfur content.

Also have used cold gun blue in the past but was disappointed in the results.

Anyone here tried these methods or have any better ideas?

 

[RobS]

There are room temperature Black Oxiding kits available like this. We use something similar on a lot of parts at work. Doesn't give a great amount of corrosion protection but for use in a shop it would be just fine /forums/images/graemlins/smile.gif

 

[RobS]

Here's some more useful info on Black Oxide finishing /forums/images/graemlins/smile.gif

 

[SnoFalls]

gun blue works good, you just have to do short batches or else it'll flake.

 

[scott_vt]

Mornin Mike,
Im with Rob on this one /forums/images/graemlins/grin.gif Black oxide is the way to go. We use it quite often on our aluminum parts.

scotty

 

[MadReferee]

Check with Brownells. They are a gunsmith supply house and probably have several different chemicals and processes that will work. One nice thing about Brownells is that you can usually buy small quantities of their stuff.

Brownells

 

[PineRidge]

Rob the Caswell chemicals look like they should do the job for my application. Since you use the product at work let me ask you if you use a timer for the parts in the solution or just keep a close eye on the color change until they reach the desired deep color?

 

[RobS]

Actually Mike, we use a product called PrestoBlack by Birchwood Casey but for some reason our firewall wouldn't let me into their site. I don't use the stuff myself, only have seen it in the shop. There is a hot plate under one of the "tanks" (more like a metal bucket) but I don't think it's as hot as the hot black oxide process uses.

I'm also under the impression that the times in the various baths are not that critical. If you want, I'm sure I could find out more about it, let me know /forums/images/graemlins/smile.gif

 

[hbarski]

Mix a little lemon juice in with a tablespoon of mayonnaise. I use it to blacken knife blades and such. Just let it react for a few days. Gives a kind of case hardened look.

 

[Inspector507]

Birchwood Casey's website