Looking for a specific socket head cap screw...

[BrooklynBravest]

Ok, so my firefighting training prop I have been working on for some time now, is nearing completion.

I just sent it to powdercoat, praying I didn't make any mistakes... (would cost me $300).

Anyway, the color is going to be safety orange and I want it to have black pieces.

It has 8 bolts on the face that I would like to be black.

Here is where the problem comes in... Its going to potentially face the elements and more likely going to face firefighter hoses during training. So. black oxide is out.

What I need is a 3/8" - 16, by 2.5" length socket head cap screw. Black Oxide stainless 18-8 would be ideal but McMaster only sells those up to 1.5" long.



In addition, these bolts will be removed and reinstalled periodically depending on how you wish to configure the prop. Right now I am using a washer on either side with a lock washer and hex nut on the thread side.

Would a serrated flange nut be sufficient to eliminate the lock washer? I considered nylon lock nuts but they tend to be irritating to thread most of the way by hand once you hit the nylon. I want the process of reconfiguring the prop to be painless as possible.

[pete]

There's a couple of methods of blackening stainless but I don't think it's possible in the average home shop. If you get really stuck maybe checking around on some of the better known custom gunmakers sites to find someone who can do the same on stainless actions and barrels might work for you if you can't find them off the shelf? Yeah it's gonna slow things down but it's one route. Have you checked any other suppliers? Dunno maybe a supplier to the home built aircraft hobbiest's might have them? That's a fairly specialized fastner and no doubt there's a premium price slapped on them as well. Stainless is only rust resistant tho and if there in contact with water I'd expect at least some minor rust or discoloration to develop over time.

They do make titanium bolts and those are pretty much good in any environment. Not sure if they can be anodised or if there available with a black coating off the shelf. Those nylock nuts have a limited number of cycles before they no longer work as lock nuts for what that's worth. Sorry I can't be of more help.

[John Evans]

Stainless fasteners are generally a poor choice for repetitive bolt .unbolt apps as most all stainless to stainless will gauld sooner or later. Use zinc plated grade 5 with the flanged nuts and be done with it. If these things are going to be taken apart and reconfigured regularly you can bet the fasteners will be lost and replaced with whatever!

[BrooklynBravest]

Think it's worth just painting the heads on zinc?

It will still only be the color I want on one side though

Also considering powdercoating them myself?

[John Evans]

First time you put a wrench on a painted bolt head bye bye paint and powder coat won't be much better.Black oxcide would be better,and that is the std. finish for Allen head caps.

[BrooklynBravest]

It's going to rust instantly though

I want to use black oxide.

Technically other parts of the prop are going to rust though. The powdercoat will chip when the prop is hit with tools and the bare steel will rust all the same.Maybe il just use black oxide so it looks good for sale purposes.

People will lose and change out the bolts anyway

[Magicniner]

Try a bright zinc plated fastener treated with G96 Gun Blue, it blacks the surface of zinc parts quite well,

- Nick

[BrooklynBravest]

I considered gun blue but it seems like an excessive amount of work for production.

[SteveM]

If you are doing a lot of assembly / disassembly, consider using some anti-seize compound on them.

You can get it at any auto parts store. It is typically used for header / exhaust fasteners so that you can get them apart years after assembly.

A little will go a long way - I've owned the same 4-oz bottle for 30 years.

Using the serrated fasteners will rip the hell out of the powder coating. At least using a serrated washer, the washer will dig into the powder coat and stop rotating while the fastener head rotates on the washer.

Steve

[Magicniner]

I considered gun blue but it seems like an excessive amount of work for production.

You could use the black fasteners and use an old electric deep fat fryer to coat them with a beeswax/grease/30 weight oil mix.
Patches of the bare steel base plate for my reloading press that have been contaminated with my home brewed bullet lube have refused to corrode despite my efforts to clean it off

- Nick

[reggie_obe]

Either source the bolts with a Yellow Zinc plating or send the existing fasteners out to be stripped and Cadmium plated. Either will hold up to water better than anything that has been suggested other than a good grade of stainless which comes with its own problems. Functionality and longevity should be more important than color.

[Harold_V]

Cad plating is pretty much non-existent today, due to its toxicity.

Harold