Heat treatment
Heat treatment
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?
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Re: Heat treatment
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.
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.
Re: Heat treatment
Don't do it unless you have a boxful to try.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?
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
J Bro
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Re: Heat treatment
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.
Re: Heat treatment
Points taken - painting it is then. Pity, it would have been interesting to try something new.
Re: Heat treatment
You could try chemical blackening - Kurust isn't a bad way to start.
Re: Heat treatment
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.
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.
Re: Heat treatment
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.
Re: Heat treatment
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?
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?
Re: Heat treatment
Remove crown race
https://youtu.be/9G5R8-qitgM
Remove and Install headset
https://youtu.be/yAXFyfBJhKU
https://youtu.be/9G5R8-qitgM
Remove and Install headset
https://youtu.be/yAXFyfBJhKU
Re: Heat treatment
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- ... +ascendingnirakaro 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?
Re: Heat treatment
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.
Re: Heat treatment
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.
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Re: Heat treatment
For cheapskate = read environmentally conscious. I'm very environmentally conscious....it's the Scottish blood on my fathers side.
old fangled
Re: Heat treatment
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.
Nu-Fogey