Forged chef from coil spring

[daizee]

6.5" Brute de Forge petty chef hand-forged from a 3.5" piece of truck coil spring. E/V Nautilus bearing brass bolster and white oak handle.

 

[MolokaiRider]

Beautiful work!

 

[daizee]

Thanks, M'Rider!

 

[cbach8tw]

So that would make the spring 5160? Very nice, like the handle.

 

[daizee]

Hi Cbach, probably not. This material got much harder than I would expect from 5160. I just finished another knife from a piece of Volvo station wagon coil spring, and it heat-treated VERY much like 5160, which reinforced for me that this one above, from a much larger vehicle, is likely a higher carbon (probably) alloy than 5160.

 

[cbach8tw]

Thanks

 

[milesofalaska]

Very nice.
I gave up working with steel I am not sure what it is. I now work with steel I order. But learned a lot since, so was wondering if the heat treat is similar enough not to matter a lot? Or, once you realize it is harder than expected, do you temper it an extra time, or take different care? I used to have higher carbon steels crack or warp, now guessing I just did not have a feel for it at the time. Do you get a feel for when to pull it out of the quench by how it behaves? Early on I worked with old files, leaf springs, crosscut saws, but wonder now sometimes if I simply fooled with bad steel! I'm told certain years of certain leaf springs are good, and some years 'who knows.' Same with plow blades. I assume there are well made files, and some not so great. Grind and look at the sparks helps, but just curious how you know how to treat unknown steels. Thanks.

 

[daizee]

Very nice.
I gave up working with steel I am not sure what it is. I now work with steel I order. But learned a lot since, so was wondering if the heat treat is similar enough not to matter a lot? Or, once you realize it is harder than expected, do you temper it an extra time, or take different care? I used to have higher carbon steels crack or warp, now guessing I just did not have a feel for it at the time. Do you get a feel for when to pull it out of the quench by how it behaves? Early on I worked with old files, leaf springs, crosscut saws, but wonder now sometimes if I simply fooled with bad steel! I'm told certain years of certain leaf springs are good, and some years 'who knows.' Same with plow blades. I assume there are well made files, and some not so great. Grind and look at the sparks helps, but just curious how you know how to treat unknown steels. Thanks.

Hi Miles,

My feelings on this are... If it's a very high carbon steel (O1+), I won't get all the performance out, but might get 1084-like performance (i.e. won't dissolve carbides in solution during short A-soak). I treat all these unknown steels the same to start: heat to non-magnetic, push a bit more, then quench in warm canola. This is the right protocol for 1084, and has been very effective with the others. I never quench in water or brine. No need to interrupt my quench. Of course I'm cautious about what I claim of these steels, and in fact have never sent any mystery steel off to a customer - though this big coil spring is a good candidate. I've beat on a couple knives made from it, and it's been very consistent and tough. The knife above has been fantastic in the kitchen. I did do a grain test on scrap, and do some grain refinement cycles before quench. Only takes a few minutes. If a mystery steel doesn't respond well to my fairly narrow range of heat-treat, I'm unlikely to keep working with it since I have plenty that DO work well (and 1084), and have plenty of flat stock in various air-cooled alloys as well.

Files are dangerous. I've had mixed luck with them. Every tooth is potentially a stress riser, and you can't detect cracks. They also tend to be very high carbon if they were quality. I've definitely had grain growth on some files back in earlier days. Makes a VERY toothy edge, and likely a fragile blade. By contrast, coil springs seem to show up pretty clean so far. I'd be wary of using one that had been rusting away outside for a long time. No experience with farm equipment, though I have once banged on an old railroad spike dug out of a tie that was buried in a planting bed for decades. It held together, but doesn't harden like spring or bearing steels.

I've got a set of hardness chisels from Matt Parkinson which I used to test blades of unknown steel (verified with known steel!) as they come out of temper. Start low-to-middle and add higher-temp cycles as necessary. Bearing steel (52100 and similar) needs more heat than springs so far. Their behavior gets written down for re-use later. The spring this knife is from is very large, probably 16 knives-worth, so if initial tests are good (they are!), a small investment in testing is worthwhile. If I can get good fine grain and a test piece at over 64Rc out of quench, I'm happy to keep using that steel.

Finally, I have yet to bother forging known steel except for a couple old O1 drops from other projects. Since I can order known steel in knife-appropriate thicknesses, it seems like a losing proposition to buy round or square stock only to beat it thinner by hand. They've all got to hit the grinder anyway, and results are far more consistent and predictable when starting with flat stock.