Heat treatment

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nirakaro
Posts: 1578
Joined: 22 Dec 2007, 2:01am

Heat treatment

Post by nirakaro »

I'm getting a frame powder coated, and I've taken the (threaded) headset cups out. They're black-painted steel, and the paint's flaking off. Rather than painting them again, I thought to try giving them a black patina, which involves heating them to about 300C, then quenching them in oil. Is this likely to have any negative effect on their hardness/brittleness?
Carlton green
Posts: 3650
Joined: 22 Jun 2019, 12:27pm

Re: Heat treatment

Post by Carlton green »

Without knowing what type of steel the item is made from it’s hard to know how heating and quenching will effect (degrade) or not the item’s surface hardness. I wonder too how the item will be heated and its temperature accurately controlled. It’s possible too that heating and quenching will result in a slight distortion of shape, as far as I’m concerned small distortions are not acceptable. The durability of an oil quench finish isn’t that great, IMHO.

Carbon Steel Tempering Temperatures: https://en.m.wikipedia.org/wiki/Tempering_(metallurgy)

TLDR: paint it.
Don’t fret, it’s OK to: ride a simple old bike; ride slowly, walk, rest and admire the view; ride off-road; ride in your raincoat; ride by yourself; ride in the dark; and ride one hundred yards or one hundred miles. Your bike and your choices to suit you.
jb
Posts: 1782
Joined: 6 Jan 2007, 12:17pm
Location: Clitheroe

Re: Heat treatment

Post by jb »

nirakaro wrote: 14 Oct 2021, 6:40pm I'm getting a frame powder coated, and I've taken the (threaded) headset cups out. They're black-painted steel, and the paint's flaking off. Rather than painting them again, I thought to try giving them a black patina, which involves heating them to about 300C, then quenching them in oil. Is this likely to have any negative effect on their hardness/brittleness?
Don't do it unless you have a boxful to try.
300° is at tempering temperature and bearing tracks are very hard. Re-tempering can cause cracking.
Last edited by jb on 14 Oct 2021, 9:35pm, edited 1 time in total.
Cheers
J Bro
rogerzilla
Posts: 2887
Joined: 9 Jun 2008, 8:06pm

Re: Heat treatment

Post by rogerzilla »

I've done this to small components in the past and they have resisted rust well. I went to cherry heat before dropping them in oil. Never tried bearing surfaces.
nirakaro
Posts: 1578
Joined: 22 Dec 2007, 2:01am

Re: Heat treatment

Post by nirakaro »

Points taken - painting it is then. Pity, it would have been interesting to try something new.
hamster
Posts: 4131
Joined: 2 Feb 2007, 12:42pm

Re: Heat treatment

Post by hamster »

You could try chemical blackening - Kurust isn't a bad way to start.
nirakaro
Posts: 1578
Joined: 22 Dec 2007, 2:01am

Re: Heat treatment

Post by nirakaro »

Thing is, it looks like I could buy a complete new headset for less than the price of a bottle of Kurust!
While we're on the subject, is there a technique for removing the bottom bit of the lower bearing, that's a very tight fit on the steerer tube? Not necessary I suppose, but it would be nice to know I could.
nsew
Posts: 1006
Joined: 14 Dec 2017, 12:38pm

Re: Heat treatment

Post by nsew »

Thats the crown race. Gently tap out with a large screwdriver and mallet moving from one side of the race to the other. Can be re-fitted with suitable width pipe. For the price of having a shop re-fit the headset, the tools can be found cheaply online. Plenty of how-to’s available.
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nirakaro
Posts: 1578
Joined: 22 Dec 2007, 2:01am

Re: Heat treatment

Post by nirakaro »

Hmmm, the crown race, glad to know what it's called. And it has a seal? There wasn't one of those when I took it apart. Maybe that's why the
bearing was looking a bit sorry for itself. Is that a generic thing that I can just get one and fit it? Or more complicated than that?
nsew
Posts: 1006
Joined: 14 Dec 2017, 12:38pm

Re: Heat treatment

Post by nsew »

Remove crown race

https://youtu.be/9G5R8-qitgM

Remove and Install headset

https://youtu.be/yAXFyfBJhKU
nsew
Posts: 1006
Joined: 14 Dec 2017, 12:38pm

Re: Heat treatment

Post by nsew »

nirakaro wrote: 15 Oct 2021, 3:16pm Hmmm, the crown race, glad to know what it's called. And it has a seal? There wasn't one of those when I took it apart. Maybe that's why the
bearing was looking a bit sorry for itself. Is that a generic thing that I can just get one and fit it? Or more complicated than that?
The three headsets I’ve fitted had seals there. If the bearing races are smooth then you can fit new loose balls of the size in the current retainer. About 25 on each race, leave about a one ball gap. Requires some skills to assemble correctly. You could fit a new headset for the paint job? I guess it’s 1”? Tange and Stronglight headsets are not expensive and well made. You’ll need to pay attention to stack height. https://www.sjscycles.co.uk/headsets-1- ... +ascending
nsew
Posts: 1006
Joined: 14 Dec 2017, 12:38pm

Re: Heat treatment

Post by nsew »

If you purchase a new headset you’ll also need to know the crown race diameter of the old one. 27.0 is JIS (Japanese) standard and 26.4 ISO (International). Digital calliper job.
nirakaro
Posts: 1578
Joined: 22 Dec 2007, 2:01am

Re: Heat treatment

Post by nirakaro »

Nah, this bike seems to have survived thirty-odd years without a seal, and was still perfectly rideable. So I'm too much of a cheapskate to get a new headset, I'll just strip it down and regrease it every couple of decades.
hoogerbooger
Posts: 673
Joined: 14 Jun 2009, 11:27am
Location: In Wales

Re: Heat treatment

Post by hoogerbooger »

For cheapskate = read environmentally conscious. I'm very environmentally conscious....it's the Scottish blood on my fathers side.
old fangled
colin54
Posts: 2529
Joined: 24 Sep 2013, 4:34pm

Re: Heat treatment

Post by colin54 »

I've had success using a thin bladed knife to remove the crown race, placing the sharp edge at the base of the race and tapping on the back of the blade at different points around the fork, the knifes blade acts as a gentle wedge, bringing the race off nice and straight.
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Nu-Fogey
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