Oil blackening a carriage bolt head

[Perplexed]

I’m planning to use a 1/4-20 carriage bolt for my latest hassock fan project, but I wanted a dark finish instead of the zinc plated appearance of the factory bolt. I turned down the head on my lathe to get rid of the casting numbers, then trimmed the edge a bit. After that, I heated the head with a butane torch till almost red hot, and dunked the bolt into a tub of used motor oil. Here’s the result compared to an untouched bolt. I think it’s a pretty neat way to darken steel other than painting it…

 

[trekrok]

I’m planning to use a 1/4-20 carriage bolt for my latest hassock fan project, but I wanted a dark finish instead of the zinc plated appearance of the factory bolt. I turned down the head on my lathe to get rid of the casting numbers, then trimmed the edge a bit. After that, I heated the head with a butane torch till almost red hot, and dunked the bolt into a tub of used motor oil. Here’s the result compared to an untouched bolt. I think it’s a pretty neat way to darken steel other than painting it…

View attachment 544748

It won't matter for your use, cut does it affect the hardening of the bolt? Looks good.

 

[Mr.Glock]

I had planned on doing the same thing today. I put a set of light brackets on my Jeep and the bolts that came with the kit are so contrasting to the black mounts themselves. But have just been sitting on my ass all day, other than frisbee with the dog!

 

[Perplexed]

It won't matter for your use, cut does it affect the hardening of the bolt? Looks good.

It depends on the steel alloy being used and how hot you get the steel. In some cases, the metal becomes more brittle, on other cases, it’s largely unaffected. In my situation, as you surmised, it’s irrelevant since the bolt won’t be subject to any stress in any appreciable fashion.

 

[Perplexed]

I had planned on doing the same thing today. I put a set of light brackets on my Jeep and the bolts that came with the kit are so contrasting to the black mounts themselves. But have just been sitting on my ass all day, other than frisbee with the dog!

View attachment 544761

In your situation, I’d probably bead blast the bolt heads to strip the clearcoat and give the surface a bit of “teeth,” then primer and paint. In your application, there are stress forces in different directions, so I’d be hesitant to apply a large amount of heat to the bolts. Others here with more experience may chime in.

 

[Mr.Glock]

In your situation, I’d probably bead blast the bolt heads to strip the clearcoat and give the surface a bit of “teeth,” then primer and paint. In your application, there are stress forces in different directions, so I’d be hesitant to apply a large amount of heat to the bolts. Others here with more experience may chime in.

No stress on these mounting bolts. Was just going to dark em up a bit.

 

[Perplexed]

No stress on these mounting bolts. Was just going to dark em up a bit.

Don’t go off road, huh?

 

[Mr.Glock]

Don’t go off road, huh?

I have them torqued in with anti seize. I might just black permanent marker most likley! LOL!