Author Topic: Softening steel  (Read 668 times)

zahc

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Softening steel
« on: May 04, 2021, 07:20:56 PM »
I want to turn the teeth of of a small (13tooth) bike track sprocket with a lathe.

I'm pretty sure they are hardened chrome moly. So they won't turn. Can I heat it up to a certain color and let it air-cool to anneal it? I don't have an oven, just a torch.
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Boomhauer

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Re: Softening steel
« Reply #1 on: May 04, 2021, 07:23:26 PM »
Get a tempil stick for the temp you need to heat it to so you don’t overdo it
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Jim147

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Re: Softening steel
« Reply #2 on: May 04, 2021, 07:31:22 PM »
Get a tempil stick for the temp you need to heat it to so you don’t overdo it

Thats the right way but I just heat it up to just red and let it cool off.
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Re: Softening steel
« Reply #3 on: May 04, 2021, 07:36:44 PM »
If you do it just right the teeth will melt off and you won't need to turn them, follow me for more tips.

bob

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Re: Softening steel
« Reply #4 on: May 04, 2021, 07:45:47 PM »
Depending on the alloy, critical temp is going to be somewhere around 1200-1400F, heat it to that and let it cool slowly, preferably insulated and overnight.
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griz

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Re: Softening steel
« Reply #5 on: May 04, 2021, 07:48:39 PM »
Just out pf curiosity, why do you want a toothless sprocket?
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zahc

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Re: Softening steel
« Reply #6 on: May 04, 2021, 07:58:23 PM »
I just want the inside part that screws onto the hub. The teeth are 1/8 wide and I need them to be skinny to fit a skinny chain. So I plan to turn a regular sprocket down into a hub then silver braze a narrow 8 speed cog back on. Alternately I could turn the teeth down narrower instead. Or I could have one laser cut.
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zxcvbob

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Re: Softening steel
« Reply #7 on: May 04, 2021, 08:21:25 PM »
What about using a grinder instead of a turning tool?  Just go slow.  You could still use the lathe to keep it concentric, although it might be easier to grind most of it off freehand.
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griz

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Re: Softening steel
« Reply #8 on: May 04, 2021, 09:05:29 PM »
I just want the inside part that screws onto the hub. The teeth are 1/8 wide and I need them to be skinny to fit a skinny chain. So I plan to turn a regular sprocket down into a hub then silver braze a narrow 8 speed cog back on. Alternately I could turn the teeth down narrower instead. Or I could have one laser cut.

I kind of thought that would be the goal.  My only advice would be the same as Bob's, chuck it in the lathe and use a grinder to evenly take the teeth off.  That has the advantage of not having to take the temper out, but doesn't give you as much dimensional control.  Good luck.
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HankB

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Re: Softening steel
« Reply #9 on: May 04, 2021, 11:15:26 PM »
Is the quench temperature the same as the annealing temperature? If so, can't you judge the temp is "about" right once the steel loses its magnetic properties?
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Re: Softening steel
« Reply #10 on: May 04, 2021, 11:20:43 PM »
Lathe, put something over the ways to catch the debris, and grind with something held in your toolpost. Or, do you know anyone with a milling machine and a rotary table?
 
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