tempering metal........

[bob1961]

i need to run 3mm threads on some 1/8" cold rolled solid rod for pinion gear shaft and want to harden them after threads are done....what temp/color do i heat the metal up to and what oil should i use to dunk them in, what method does any body here use........bob

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[AX10wannabe]

trying to remember what we did in school for making knives in metal fab class.. umm... we heated it up with a ace/oxy torch until it was glowing then dunked it in just regular engine oil i think if i remember correctly. not sure though.

[bob1961]

yeah i have an idea but wasn't sure with the small rod i need to do it to....i made a threaded shaft for a pinion gear on a servo for a winch....but the 1/8" rod i have from home depot has gouges in it from the set screw, just want to harden/temper the rod a bit........bob

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[leather]

Heat it until a magnet won't attract to it anymore and then quench it in oil. Go straight down, not on an angle, and move in and out like that for a couple of seconds.

[j-bird]

Heat it the first time to glowing red and let it cool then heat it just till it starts to turn colors the second time and then cool it in oil .. The second heat is the most critical don't over heat it.. Just before it starts to glow I seen this just the other day.. If you put glowing red steel in oil you're gonna having a fire


J-bird

[leather]

If you dunk the glowing steel in oil it will be okay. You have to vaporize oil to burn it. So if you put it in slow or pull it out while still red you could possibly have a problem. Then you would be vaporizing the oil but a straight swift dunk is fine. You can throw lit matches in a bucket of diesel fuel all day and it won't do anything. I work on oil burners and have done this to prove how hard it actually is to burn oil to my customers.

[Meatwad]

For a simple case hardening, carbon and water quenching has worked for me. Sugar and/or ground animal bone then dunk in water, repeat a couple times. Backyard engineering at its best.

[bob1961]

thx guys, i just want to make the shaft a little harder so the set screw bites a bit better and not sink into it....not much material on an 1/8" shaft to make a flat spot like a 5mm.......bob

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[65BAJA]

Doesn't the base metal have to have a certain amount of carbon in it's alloy composition to be heat treatable? Does cold rolled steel have enough carbon to make this effective?

[SlickRockSpider]

Cold rolled material wont heat treat. Case hardening is your best bet . Take test piece and try.



Evan

[bob1961]

like i said it's just home depots 1/8" solid rod they sell, not sure what it is really cold or hot rolled....testing coming up folks, thx all ....i need to thread that size rod, but then want it to last....not sure what hardened 1/8" rod that i can thread without killing my 3mm dia....i'm looking to find a good piece of metal at a lower cost for a product to sell here and going through product development at this time....i don't want to sell junk .......bob

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[65BAJA]

You might be able to buy annealed chrome-molly rod. Do your machining to it. Then have it heat treated.

[Charlie-III]

Good question bob......

I do know that I used to use a base metal that was labeled "oil hardening steel" that was reasonably machineable, but could be hardened later. Just DON'T overheat it while machining, then it gets too hard!

Cast iron is similar, not to bad to machine, but get it too hot & it becomes a PITA.

[dkf]

Originally Posted by bob1961

like i said it's just home depots 1/8" solid rod they sell, not sure what it is really cold or hot rolled....testing coming up folks, thx all ....i need to thread that size rod, but then want it to last....not sure what hardened 1/8" rod that i can thread without killing my 3mm dia....i'm looking to find a good piece of metal at a lower cost for a product to sell here and going through product development at this time....i don't want to sell junk .......bob

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Its probably 1018 CRS. Cold rolled will not have mill scale on it, hot rolled (A36) will usually have a thin hard blackish scale on it and be easier to bend. A 1045 or even 1095 will get nice and hard by just heating it up orange hot and quenching it in water.(1045 and 1095 will get a little too hard for a set screw to grip real good actually) The 1018 will not get very hard without introducing carbon into the surface. For hardening 1018 I use Kasenit case hardening compound. You can however add some hardness to 1018 by heating it up and quenching it in water, a brine solution (water and salt) or even your own piss. For your purpose just quenching in either of those 3 should work ok.

1018 CRS - .18 % carbon
1045 CRS - .45 % carbon
1095 CRS - .95 % carbon

Tool steel almost always comes in annealed form whether it be O-1, A-2, S-7, W-1, D-2 and etc. For long thin parts I like to use A-2 to minimize warpage. If I want something that is heat treated but still machinable I'll use a 4140 prehard. Its prehardened to 28-30Rc which will machine with HSS tooling no problem.

[bob1961]

thx for the numbers of the steel and what each will take ........bob

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[Mr.Joshua]

even your own piss.

Sounds messy...and potentially dangerous
J/k that's some very useful info dkf.

Let us know what works Bob

[Charlie-III]

dkf, nice info, thanks for sharing!!