Thread: Leaf springs for tool steel

KRH - I can't give you any advice myself, but I know that Andy Mac has made blades for a few of his planes from leaf springs. If you can't get in touch with him let me know and I'll give him a call.

If you search the forums you will find a heap of stuff on this topic.

AndyMac and Schtoo (from Japan) have something to say in this thread.

http://www.woodworkforums.ubeaut.com...757#post262757

Hi KRH,

Using leaf springs from cars for things like plane blades and chisels is a bit of a compromise, as the carbon content is around about 0.6% (5160 is a standard carbon-chromium steel used in auto springs, with a carbon content around 0.56 - 0.64%), not really in the league of proper tool steels at 0.9% with extra alloys. It can't be hardened as much, but it can be used, and I've made a number of blades using recycled springs. There are two ways of going, either buy unused annealed stock off-cuts from a spring works (flat and nice 'n' easy to work cold), or work used spings. There is a risk if using damaged stuff, with cracks or delaminations, but I've only come across that in coil springs.
Here's a general rundown on how I go about it, no details about sizes or angles etc. Note I'm not a trained blacksmith, toolmaker or metalurgist...I just make tools for the simple satisfaction of using them, and enjoy recycling.
First thing is to straighten the curve, by either:
1/ heating it on the forge past full cherry to orange/yellow (approx. 1175degrees C) and beat it flat. Never hammer unheated springs, they will break, and don't dent it with the hammer as there will be more work later. Cut it to size on the hardy.
2/ anneal the thing, for 5160 that's about 785degrees C and cherry red, the book says air cool but I bury it in Kaowool or vermiculite to slow the cooling.
You could go on to shape it with a cut-off saw and/or grinder but I try to avoid using them as there is a high chance of localised overheating, which ruins the carbon content. If you do stuff like oxy cutting or high speed cutting you'll need to stress relieve by annealing.
Another, more traditional approach is to forge the blade to shape, including the cutting bevel. Finish with a flatter, then anneal before cold working.
My preferred option is to hand work the annealed metal, with lots of hacksawing and filing....a good quality hacksaw is worth its weight in gold! If I'm doing it at work and the stock is thick I'd probably cut the bevel on the drop bandsaw, which has a nice accurate and cool cut. I finish the bevel on my water grinder, but leave a thick edge so it doesn't burn during heat treatment.
Once you're satisfied with the finish, you go onto heat treatment. Normalize any stresses introduced before going onto hardening. 5160 has a hardening temp. of 830degreees C, that's around a bright cherry red, and quench in oil (careful of flashback!). You may only need to do the first 20-30mm, so the edge is hard and the body is softer. The metal is now hard, too hard really and will be brittle, so onto tempering. Clean the scale so you can see the steel underneath to observe the colours. According to spec's, the tempering range for spring steel is between 425 and 700degrees C, depending on intended use. I temper plane blades to dark straw, which is only about 250degrees C, using oxy acetylene torch, but others (like Schtoo) use a conventional oven in the house. Basically I think that the discrepancy in temperatures means the steel is still too hard for its intended use, that of a springy action (because it retains its near fully hard state), but as we've commandeered the steel for another purpose it doesn't really matter.
Buff off any crud from heating then go onto lapping the blade and sharpening as per normal blades. There is a chance the heat treatment has waped the thing! It probably won't hold an edge as well as a quality commercial blade, but they don't have the same satisfaction.

Good luck

Are leaf springs are ok for knifes?

For knives...depends

I have a big heavy kukhri forged from a leaf spring--for chopping its fabulous but its also about 5-6mm across the spine. For smaller blades I would not be so keen because of the lower stiffness. You would do better with a higher carbon steel like 1095 or O1.

If you are interested in knife making I strongly recommend popping across to www.bladeforums.com They have a lot of information and FAQs there (for obvious reasons ) and are also a pretty helpful lot. I mainly do my own hafting but am dipping in my toe to blade making and Ive learned a lot from the forums there.

Originally Posted by Andy Mac

Hi KRH,

Using leaf springs from cars for things like plane blades and chisels is a bit of a compromise, as the carbon content is around about 0.6% (5160 is a standard carbon-chromium steel used in auto springs, with a carbon content around 0.56 - 0.64%), not really in the league of proper tool steels at 0.9% with extra alloys. It can't be hardened as much, but it can be used, and I've made a number of blades using recycled springs. There are two ways of going, either buy unused annealed stock off-cuts from a spring works (flat and nice 'n' easy to work cold), or work used spings. There is a risk if using damaged stuff, with cracks or delaminations, but I've only come across that in coil springs.
Here's a general rundown on how I go about it, no details about sizes or angles etc. Note I'm not a trained blacksmith, toolmaker or metalurgist...I just make tools for the simple satisfaction of using them, and enjoy recycling.
First thing is to straighten the curve, by either:
1/ heating it on the forge past full cherry to orange/yellow (approx. 1175degrees C) and beat it flat. Never hammer unheated springs, they will break, and don't dent it with the hammer as there will be more work later. Cut it to size on the hardy.
2/ anneal the thing, for 5160 that's about 785degrees C and cherry red, the book says air cool but I bury it in Kaowool or vermiculite to slow the cooling.
You could go on to shape it with a cut-off saw and/or grinder but I try to avoid using them as there is a high chance of localised overheating, which ruins the carbon content. If you do stuff like oxy cutting or high speed cutting you'll need to stress relieve by annealing.
Another, more traditional approach is to forge the blade to shape, including the cutting bevel. Finish with a flatter, then anneal before cold working.
My preferred option is to hand work the annealed metal, with lots of hacksawing and filing....a good quality hacksaw is worth its weight in gold! If I'm doing it at work and the stock is thick I'd probably cut the bevel on the drop bandsaw, which has a nice accurate and cool cut. I finish the bevel on my water grinder, but leave a thick edge so it doesn't burn during heat treatment.
Once you're satisfied with the finish, you go onto heat treatment. Normalize any stresses introduced before going onto hardening. 5160 has a hardening temp. of 830degreees C, that's around a bright cherry red, and quench in oil (careful of flashback!). You may only need to do the first 20-30mm, so the edge is hard and the body is softer. The metal is now hard, too hard really and will be brittle, so onto tempering. Clean the scale so you can see the steel underneath to observe the colours. According to spec's, the tempering range for spring steel is between 425 and 700degrees C, depending on intended use. I temper plane blades to dark straw, which is only about 250degrees C, using oxy acetylene torch, but others (like Schtoo) use a conventional oven in the house. Basically I think that the discrepancy in temperatures means the steel is still too hard for its intended use, that of a springy action (because it retains its near fully hard state), but as we've commandeered the steel for another purpose it doesn't really matter.
Buff off any crud from heating then go onto lapping the blade and sharpening as per normal blades. There is a chance the heat treatment has waped the thing! It probably won't hold an edge as well as a quality commercial blade, but they don't have the same satisfaction.

Good luck

Thanks Andy. That is a great response. It appears a bit more complicated than I initially thought, probably because I have never done any like work before. But sounds an interesting exercise so I might give it a go.

Regards

Ken

Hi all

I’m a professional blacksmith that specializes in knife and tool making, living in the Adirondacks in new york

this is likely a repeat of a previous excellent post *points above* but its the standard article I've cut and pasted over the years to help folks, as this is a common question.
In fact looking over the gents post I think we only disagree on the ability to work leaf cold, anyway here ya go for your perusal

there’s ALOT of misconceptions about working steel and what’s known as scrap yard steel i.e. leaf springs, coil springs etcetc.
There’s also some confusion about the terms annealing normalizing hardening and tempering.
Lets start with the composition of leaf and coil

its BOTH 5160 and 1095, depends entirely on the automaker but both are VERY suitable for tool and knife making, in fact if your NOT a blacksmith by trade your much better off using them as their both VERY forgiving steels when it comes to variance in heats while working and treating.

Modern myths about used spring steel.
Good luck trying to crack spring steel on an anvil while working it cold. NOT going to happen. In fact I've straightened entire sections with a sledge before forging.

There are no "micro stress" fractures or delaminating in these steels.
What people commonly mistake for a "micro stress" fracture is actually an almost complete break in the steel or a piece that’s been overworked between normalizations. Mind you you shouldn’t HAVE to normalize steel while forging, if you are your working it WAY too much at low temperatures... i.e. your working very hard instead of smart to move the metal. Keep it HOT.

Delamination in homogenous steel is an oxymoron. Unless you've stumbled upon a piece of wrought iron which has layers of iron and silicates and WILL delaminate if not worked at a high enough temperature, its impossible to delaminate something that’s homogenous, and all modern steels ARE homogenous. If you ARE lucky enough to stumble on something that looks like layers coming apart under your hammer while working it at a dull cherry, place it aside and cherish it <!--[if gte vml 1]><v:shapetype id="_x0000_t75" coordsize="21600,21600" o:spt="75" oreferrelative="t" path="m@4@5l@4@11@9@11@9@5xe" filled="f" stroked="f"> <v:stroke joinstyle="miter"/> <v:formulas> <v:f eqn="if lineDrawn pixelLineWidth 0"/> <v:f eqn="sum @0 1 0"/> <v:f eqn="sum 0 0 @1"/> <v:f eqn="prod @2 1 2"/> <v:f eqn="prod @3 21600 pixelWidth"/> <v:f eqn="prod @3 21600 pixelHeight"/> <v:f eqn="sum @0 0 1"/> <v:f eqn="prod @6 1 2"/> <v:f eqn="prod @7 21600 pixelWidth"/> <v:f eqn="sum @8 21600 0"/> <v:f eqn="prod @7 21600 pixelHeight"/> <v:f eqn="sum @10 21600 0"/> </v:formulas> <vath o:extrusionok="f" gradientshapeok="t" o:connecttype="rect"/> <o:lock v:ext="edit" aspectratio="t"/> </v:shapetype><v:shape id="_x0000_i1025" type="#_x0000_t75" alt="" style='15pt; 15pt'> <v:imagedata src="file:///C:/DOCUME~1/tgdw/LOCALS~1/Temp/msoclip1/01/clip_image001.gif" o:href="https://www.woodworkforums.com/images/smilies/happy/biggrin.gif"/> </v:shape><![endif]--><!--[if !vml]--><!--[endif]-->, true wrought iron isn’t industrially made anymore and is a limited commodity i.e. antique for all intents and purposes.

Heat-treating and terms.

After working the metal to the desired shape you’ll want to anneal the metal.
Air-cooling of the stock from a non- magnetic state.
I use an old stereo speaker magnet speaker side down as a magnetic gauge.

Heat the piece to a dull to cherry red ant see if it will attract to the magnet, chances are it will so heat it a tad more and try again.
The reason for this approach is that no two forges lighting conditions are the same and so gauging by color can be dicey.
Once the piece is not attracted to the magnet then stick it in a vice using as little stock as possible on a non cutting area of said piece, for example on a knife you’d use the very end of the tang.
The piece is now really for any file work and polishing, yes you want to polish it to at least a 120 at this phase. Its ALOT easier to remove file marks at this stage.

Anneal.... heat to non-magnetic and bury in a non-reactive insulative material i.e. vermiculite, dry sand, CLEAN ash, until room temperature. Do this step at LEAST twice to insure no warpage for the next step.

Harden.... bring back up to non-magnetic and quench in oil


let blade cool then polish back up so you can gauge the colors that will develop in the next step

temper..... Get your forge going, lay the blade with the spine making contact with the coals (keep the tip above the coals or lay on a piece of green coal to prevent it from heating too quickly as its thinner than the spine) OR lay it on red hot stock, or grab it with tempering tongs that are heated up to red hot.... watch the colors develop on the blade. When the spine is blue and the edge is yellow, quench in heated oil. What you’ve just done is drawn the hardness OUT of the spine while retaining the edge temper, that way your blade holds a edge but is not brittle.


Remember to anneal a few times, if you can get the blade to anneal without warpage then the crystalline structure is fairly even and you wont be as likely get warpage during quench, if it warps during any of the stages previous to the tempering, heat it up, straighten it, start over with normalizing and file work.


Good luck!

this may be a double post if so apologies, and what the heck here lemme throw in a pic or two

these were both made from leaf spring, mind you their both still not done and are works in progress






now onto the whole leaf sring thing, although mind you it looks like a gent above covered it fairly well and we only sem to disagree on its suitability, *i LOVE the stuff* and the ability to cold work the stock before forging.

Hi all

I’m a professional blacksmith that specializes in knife and tool making, living in the Adirondacks in new york

this is likely a repeat of a previous excellent post *points above* but its the standard article I've cut and pasted over the years to help folks, as this is a common question.
In fact looking over the gents post I think we only disagree on the ability to work leaf cold, anyway here ya go for your perusal

there’s ALOT of misconceptions about working steel and what’s known as scrap yard steel i.e. leaf springs, coil springs etcetc.
There’s also some confusion about the terms annealing normalizing hardening and tempering.
Lets start with the composition of leaf and coil

its BOTH 5160 and 1095, depends entirely on the automaker but both are VERY suitable for tool and knife making, in fact if your NOT a blacksmith by trade your much better off using them as their both VERY forgiving steels when it comes to variance in heats while working and treating.

Modern myths about used spring steel.
Good luck trying to crack spring steel on an anvil while working it cold. NOT going to happen. In fact I've straightened entire sections with a sledge before forging.

There are no "micro stress" fractures or delaminating in these steels.
What people commonly mistake for a "micro stress" fracture is actually an almost complete break in the steel or a piece that’s been overworked between normalizations. Mind you you shouldn’t HAVE to normalize steel while forging, if you are your working it WAY too much at low temperatures... i.e. your working very hard instead of smart to move the metal. Keep it HOT.

Delamination in homogenous steel is an oxymoron. Unless you've stumbled upon a piece of wrought iron which has layers of iron and silicates and WILL delaminate if not worked at a high enough temperature, its impossible to delaminate something that’s homogenous, and all modern steels ARE homogenous. If you ARE lucky enough to stumble on something that looks like layers coming apart under your hammer while working it at a dull cherry, place it aside and cherish it <!--[if gte vml 1]><v:shapetype id="_x0000_t75" coordsize="21600,21600" o:spt="75" oreferrelative="t" path="m@4@5l@4@11@9@11@9@5xe" filled="f" stroked="f"> <v:stroke joinstyle="miter"/> <v:formulas> <v:f eqn="if lineDrawn pixelLineWidth 0"/> <v:f eqn="sum @0 1 0"/> <v:f eqn="sum 0 0 @1"/> <v:f eqn="prod @2 1 2"/> <v:f eqn="prod @3 21600 pixelWidth"/> <v:f eqn="prod @3 21600 pixelHeight"/> <v:f eqn="sum @0 0 1"/> <v:f eqn="prod @6 1 2"/> <v:f eqn="prod @7 21600 pixelWidth"/> <v:f eqn="sum @8 21600 0"/> <v:f eqn="prod @7 21600 pixelHeight"/> <v:f eqn="sum @10 21600 0"/> </v:formulas> <vath o:extrusionok="f" gradientshapeok="t" o:connecttype="rect"/> <o:lock v:ext="edit" aspectratio="t"/> </v:shapetype><v:shape id="_x0000_i1025" type="#_x0000_t75" alt="" style='15pt; 15pt'> <v:imagedata src="file:///C:/DOCUME~1/tgdw/LOCALS~1/Temp/msoclip1/03/clip_image001.gif" o:href="https://www.woodworkforums.com/images/smilies/happy/biggrin.gif"/> </v:shape><![endif]--><!--[if !vml]--><!--[endif]-->, true wrought iron isn’t industrially made anymore and is a limited commodity i.e. antique for all intents and purposes.

Heat-treating and terms.

After working the metal to the desired shape you’ll want to anneal the metal.
Air-cooling of the stock from a non- magnetic state.
I use an old stereo speaker magnet speaker side down as a magnetic gauge.

Heat the piece to a dull to cherry red ant see if it will attract to the magnet, chances are it will so heat it a tad more and try again.
The reason for this approach is that no two forges lighting conditions are the same and so gauging by color can be dicey.
Once the piece is not attracted to the magnet then stick it in a vice using as little stock as possible on a non cutting area of said piece, for example on a knife you’d use the very end of the tang.
The piece is now really for any file work and polishing, yes you want to polish it to at least a 120 at this phase. Its ALOT easier to remove file marks at this stage.

Anneal.... heat to non-magnetic and bury in a non-reactive insulative material i.e. vermiculite, dry sand, CLEAN ash, until room temperature. Do this step at LEAST twice to insure no warpage for the next step.

Harden.... bring back up to non-magnetic and quench in oil


let blade cool then polish back up so you can gauge the colors that will develop in the next step

temper..... Get your forge going, lay the blade with the spine making contact with the coals (keep the tip above the coals or lay on a piece of green coal to prevent it from heating too quickly as its thinner than the spine) OR lay it on red hot stock, or grab it with tempering tongs that are heated up to red hot.... watch the colors develop on the blade. When the spine is blue and the edge is yellow, quench in heated oil. What you’ve just done is drawn the hardness OUT of the spine while retaining the edge temper, that way your blade holds a edge but is not brittle.


Remember to anneal a few times, if you can get the blade to anneal without warpage then the crystalline structure is fairly even and you wont be as likely get warpage during quench, if it warps during any of the stages previous to the tempering, heat it up, straighten it, start over with normalizing and file work.


Good luck!