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Discussion Starter · #1 ·
I have a ton of spare stainless steel screws for a watch movement and I'd like to make an attempt to thermally blue them.
In the past I have had mixed results getting a consistent color and gradually heating the screw.

I think I might purchase some brass stock and see if I can get brass shavings as well.
Does anyone have any tips for accomplishing this?

I won't really have the ability to make a professional bluing tray, but I can pile the shavings on the brass sheet.
Would a thicker sheet be preferrable? Maybe 1/4" (6mm) instead of 1/8" (3mm)?
 

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I have a ton of spare stainless steel screws for a watch movement and I'd like to make an attempt to thermally blue them.
In the past I have had mixed results getting a consistent color and gradually heating the screw.

I think I might purchase some brass stock and see if I can get brass shavings as well.
Does anyone have any tips for accomplishing this?

I won't really have the ability to make a professional bluing tray, but I can pile the shavings on the brass sheet.
Would a thicker sheet be preferrable? Maybe 1/4" (6mm) instead of 1/8" (3mm)?
What is the alloy series number?

What color were you hoping to achieve?
 

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Bluing stainless is a problem because bluing is caused by the formation of a relatively thick oxide layer, and that's exactly what stainless steel is formulated to prevent. The initial layer formed on stainless is rich in chrome oxides, which seal the surface and discourage further oxidation.

It can be done but requires the metal to be held at the bluing temperature for a prolonged period (typically an hour or more) to allow time for formation of the oxides. That's not something you're likely to be able to do manually!
 

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Discussion Starter · #5 · (Edited)
Bluing stainless is a problem because bluing is caused by the formation of a relatively thick oxide layer, and that's exactly what stainless steel is formulated to prevent. The initial layer formed on stainless is rich in chrome oxides, which seal the surface and discourage further oxidation.

It can be done but requires the metal to be held at the bluing temperature for a prolonged period (typically an hour or more) to allow time for formation of the oxides. That's not something you're likely to be able to do manually!
So I'm assuming that all the manufacturers that blue their stainless parts have very precise temperature controlled ovens, which is out of the question for me.
Do you think I should purchase the thicker sheet of brass I mentioned above? Perhaps since it will take longer to heat I can achieve a more uniform color?

I just had some OK results using an extremely crude method. Vice grips and propane torch holding a steel nail (lol) directly underneath the shaft.
Feel free to laugh...I know it's not an idea method/setup. This was the first thing I found with a large surface area on top.


You can see that most of these were higher temperature around the edges because they changed to a dark purple color.
I also didn't do the best polishing job.
 

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So I'm assuming that all the manufacturers that blue their stainless parts have very precise temperature controlled ovens, which is out of the question for me.
Do you think I should purchase the thicker sheet of brass I mentioned above? Perhaps since it will take longer to heat I can achieve a more uniform color?

I just had some OK results using an extremely crude method. Vice grips and propane torch holding a steel nail (lol) directly underneath the shaft.
Feel free to laugh...I know it's not an idea method/setup. This was the first thing I found with a large surface area on top.


You can see that most of these were higher temperature around the edges because they changed to a dark purple color.
I also didn't do the best polishing job.
Hi 24h,

Do you have confirmation that they are stainless steel parts which are thermally blued?
 

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Discussion Starter · #7 · (Edited)
Hi 24h,

Do you have confirmation that they are stainless steel parts which are thermally blued?
I may actually be wrong about the "stainless" part. I've just been using that term because I didn't know any better.

1. EXPLAINED: How To Blue Steel Screws The Traditional Way ? With A Flame And Lots Of Patience | SJX Watches
2. Bluing: The Process of Thermally Treating Screws - Worn & Wound

"The corrosion resistance added by the process is highly important due to the fact that carbon steel (used for the screws) rusts easily. You'd think they would use stainless steel for the screws since stainless is highly oxidation resistant, but since the screws have a lot of torsion force applied to them when movements are being serviced, a higher hardness alloy is required."

The article goes on to say, "In watchmaking school, we treated some handmade studs with carbon enriched steel (about the same % that you would find in watch screws). The carbon in the steel makes it harder, but also reduces its ductility...Heat treatment on low carbon steel is to improve ductility, to improve toughness, strength, hardness and tensile strength and to relive internal stress developed in the material."

What Joe Horner mentioned seems to make sense. After watching a couple more videos (specifically from Clickspring on YouTube), it looks like he is using "mild steel" aka plain or low carbon steel.
 
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