I need some advice.

[BlissStreet]

Guys, I'm a little frustrated. I started a knife with some scrap from my anvil project. It sparked carbon, but never really hardened in oil or water. "Ok", I thought, "lesson learned. Unidentified scrap shouldn't be used."

So I went to a breaker yard and cheaply acquired a coil spring from a BMW. I understood that the rule of thumb is: coil springs=1095, leaf springs=5160. Both are oil quenching and are good, cheap stock to learn on. (right?)

But, as I uncoil the spring and start to work it, gaining basic skill like squaring, upsetting, drawing, shaping; two things are happening with regularity: One is that parts are falling off in the fire. Like big parts. I think it's that I'm heating it beyond it's plastic point and into it's melting stage. Ok, I get that. The other is that there are slow growth cracks forming as I work it and they continue to spread until I can bend the stock by hand and break it. I figured I was working it to cold. Ok, I get that too.

But here is the thing, the crux of my confusion. It's not consistent. One section will work wonderfully at an orange, the next will crack. So I add more heat and it melts. There seems to be no middle ground. I'm willing to admit that I am learning, but I'm watching the darned coals and steel color like a hawk. Which is why I'm shocked when 1/2 of my fledgling knife blank stay in the forge while I'm staring at a bolster and tang. or when the tang cracks like my mother during my mid teens (I wasn't an easy child)

Is it my inexperience, which I will cop to. My idiocy, which of course, I won't. Or is it some residual stresses I can't see? If so, how do I work around it?

I need a win to keep my spirits up and at the moment, this is really cramping my style. Help me, Obi Wans....well you get the drift.

[Don A]

My best advice would be to get some new known steel, like 1084, and go from there.

I have forged a lotta scrap, but it is always a gamble. Who knows what that spring had to endure in its first life.

By the way, what kind of forge are you using?

If you're using coal or charcoal, be sure your fire is plenty deep and that you're not over-doing the air.

Also remember that as the carbon content increases, your forging range decreases. High carbon is, from a non-scientific perspective, forge at orange heat, stop at red.

[MattBower]

First, I wouldn't count on that rule of thumb about springs. I had one automotive coil spring tested and it was 5160. The only rule of thumb I'd count on is that springs are usually decent blade stock.

Second, one of the hazards of salvaged steel is that you don't know anything about its condition. You seem to have considered the most likely heat-related issues that could be causing the sorts of problems you're experiencing. If it's not those (although it really does sound like you were overheating), I'm inclined to think the problem is the steel. It may have been badly overstressed at some point in its prior life.

If the spring is damaged, I don't know a reliable way to work around that. Throw it out and try another one. Or better yet, try some new, high carbon steel. One of the frustrating things about learning on scrap is that it adds extra variables and makes it harder to figure out what's going wrong. Using new steel will usually eliminate some of those variables, which makes your life a little easier when a problem crops up.

[ThomasPowers]

Is there a local spring shop you could buy "new" scrap from? Drops we call them in the USA as they are what drops on the floor when you cut a piece to size for a project. Often I can get them for scrap price plus a little boot (extra) like a hand forged trinket, or doughnuts, of in some cases a sixpack of beer; sometimes after telling them about why I want them I have to make a speedy get away as they dump free pieces in my truck faster than I can say *enough*!

Most coil over here is more like 5160 than 1095; but a manufacturer can use *anything* they think will work---and change it at anytime!

[AndersMJ]

Can't the cracking be solved by normalizing the steel 3 times, as I've seen people here suggest, before forging it?

[Steve Sells]

Steels can crack from being worked at the wrong temp, as in below or above forging range or welding range. as for normalizing before forging? umm not sure how that would repair bad metal.

[BlissStreet]

If you're using coal or charcoal, be sure your fire is plenty deep and that you're not over-doing the air.

Ahh, this certainly sounds like a portion of the problem. It was a first attempt at a forge, and I know it's not nearly deep enough. Looks like I need to rebuild it using that steel wheel that I finally got my hands on.

Also remember that as the carbon content increases, your forging range decreases. High carbon is, from a non-scientific perspective, forge at orange heat, stop at red.

I'll have to bear this in mind. Thanks.

Steels can crack from being worked at the wrong temp, as in below or above forging range or welding range.

Interesting, I assumed it would be from being worked to cold, but why does working over the forging temp crack it?

[AndersMJ]

Steels can crack from beiong worked at the wrong temp, as in below or above forging range or welding range. as for normalizing Before forging? umm not sure how that would repair bad metal.

I thought normalizing was to remove any stress in the steel before working with it?

[MattBower]

In my experience it tends to crumble more than crack at high temp. I'm not sure what causes it. Might be related to the fact that carbon lowers the melting point of iron. More carbon = lower melting point. (Not that you're actually melting your steel. I just wonder if the two things are related.)

[MattBower]

I thought normalizing was to remove any stress in the steel before working with it?

Before cold working it, or quenching it, yes. But when you heat the steel up to forging range that's going to relieve internal stresses, so normalizing beforehand doesn't do much -, if anything.

[AndersMJ]

Oh ok, thanks for clearing that up.

[Rich Hale]

I will post a wild guess here that you are forging in the sunlight or a well lit shop. If by any chance that is correct you are most likely overheating the steel. Ambient light is fine as long as you learn wot colors to look for when working in that light. A piece that looks to you to be red in sunshine may look to be really bright and about to burn in less light. You can work in any light as long s you determine by trial and error wot works for you. One other thing that may help if you get a used spring; clean it really well and either hold it up by one hand or hang it from a string, tap with a piece of metal and listen for a ring. If it has a dull sound it has cracks. Dirt or crud on it will make a dull sound also. If you are not working in bright areas nevermind wot I just wrote, but it sure seems like it is getting too hot!

[BM454]

Is there a local spring shop you could buy "new" scrap from? Drops we call them in the USA as they are what drops on the floor when you cut a piece to size for a project. Often I can get them for scrap price plus a little boot (extra) like a hand forged trinket, or doughnuts, of in some cases a sixpack of beer; sometimes after telling them about why I want them I have to make a speedy get away as they dump free pieces in my truck faster than I can say *enough*! Most coil over here is more like 5160 than 1095; but a manufacturer can use *anything* they think will work---and change it at anytime!

Thomas is right about the manufacturer. I worked in a factory which made ball joints, bolts and tie rod ends. They would use different materials to make the same parts. Depending on where they could get the wire cheaper. All they did was heat treat it in a different manner. I've got a chunk of 4140 about a foot long and around 2" dia. that came from there. It came off of a huge roll of wire. I'm hoping to make hammers from it someday if I ever get the time to do it.

[Frank Turley]

Junk yard steel is a crap shoot. You can get W1 and O1 drill rod in 3 foot lengths from MSC, McMaster-Carr, or Travers Tool catalogs. The W1 will have about 0.95% to 1% carbon content.

[BlissStreet]

I will post a wild guess here that you are forging in the sunlight or a well lit shop. If by any chance that is correct you are most likely overheating the steel. Ambient light is fine as long as you learn wot colors to look for when working in that light. A piece that looks to you to be red in sunshine may look to be really bright and about to burn in less light. You can work in any light as long s you determine by trial and error wot works for you. One other thing that may help if you get a used spring; clean it really well and either hold it up by one hand or hang it from a string, tap with a piece of metal and listen for a ring. If it has a dull sound it has cracks. Dirt or crud on it will make a dull sound also. If you are not working in bright areas nevermind wot I just wrote, but it sure seems like it is getting too hot!

While the forge itself is outdoors, the anvil is in a dark garage. Yes, there is a rather large color shift in moving from out to indoors. I'm paying even more attention to it now and getting better results.

Thomas is right about the manufacturer. I worked in a factory which made ball joints, bolts and tie rod ends. They would use different materials to make the same parts. Depending on where they could get the wire cheaper. All they did was heat treat it in a different manner.

Interesting. But the materials used in springs all have a similar profile, no? I mean, the difference between one spring steel and another shouldn't be that radical, should it?

Junk yard steel is a crap shoot. You can get W1 and O1 drill rod in 3 foot lengths from MSC, McMaster-Carr, or Travers Tool catalogs. The W1 will have about 0.95% to 1% carbon content.

I didn't get a random piece of metal in a scrap yard. I made a point of getting a spring from a car, so while there is some chance in it; I think it was the best choice short of buying new stock. Which, for me, seems a waste since I know that there will be a number of screwups. For the price, ~$20, it's what I need. Shipping new stock 1/2 around the world isn't something one does when needing basic skills material; $20 worth of metal would cost about $200 to get here. The good news is, that I can get new stock in just about any steel, size, shape and quantity I want here. I just don't see the point just yet. I figure knife #10 will put me in a position where I feel I'd do the price justice.

In other news, after a morning of appointments, I got around to putting 4 bricks around the sides of my current firepot, giving me about 5-6 inches of depth. It certainly changed the way the metal heated and how it worked. The shift in the amount of scale falling off went from about a 30% wastage to almost 0%. This really made a difference. I can see now, there is definitely a need to rebuild the forge. There is also a chance that I might have a lead on a locally built propane forge with 2 burners for around $150. Even my wife thinks I should buy one at that price. We'll see how it turns out, I have a friend that just bought one as his 2nd forge and if it works out for him, I'll place an order. With the ability to adjust the temperature range by pressure, I think it might offer more consistent results. Either way, my initial forge is too shallow and seems to be part of the issue.

I can't thank you guys enough for the insights.

[Steve Sells]

as for your similar profile theory , take 1060, 1095 and 5160, these are all used for springs, one has 0.80 Chromium and a few degrees higher hardening temp for ideal conversion than the others. Another is a few degrees lower hardening temp than the others. One needs water for good hardening, another one is a problem in water, the other can be hardened safely in either. I aint telling which is which, as they are all the same right ? But I have posted them in other places in this forum, if you read up you will find it. Welcome to the wonders of mystery metals from buying used stock.

[BlissStreet]

as for your similar profile theory , take 1060, 1095 and 5160, these are all used for springs, one has 0.80 Chromium and a few degrees higher hardening temp for ideal conversion than the others. Another is a few degrees lower hardening temp than the others. One needs water for good hardening, another one is a problem in water, the other can be hardened safely in either. I aint telling which is which, as they are all the same right ? But I have posted them in other places in this forum, if you read up you will find it. Welcome to the wonders of mystery metals from buying used stock.

Point taken

[pkrankow]

Funny thing is I have four coil springs pulled off one car at the same time...I expect to have some trial and error when I start using them. I have another coil spring I am still working though, and it wants a more aggressive quench than oil.

Phil

[MattBower]

I don't know anything about steel prices in South Africa, but I can get five feet of 1/4"x1-1/2" 1080 from Admiral Steel for around $20, and I'll know with pretty good certainty what I have and what condition it is in. Then I can look up (if need be) how to heat treat it properly, without having to guess at what it is. And I can make quite a few knives from that.

The thing is, learning to heat treat well -- if you choose to do your own heat treating -- is a huge part of making good knives. And as long as you're rolling the dice with regard to what steel you have, you're also rolling the dice as far as proper heat treating. It's harder to learn that way. Did it crack because I overheated it, or because of a mechanical flaw that it incurred in its former life as a spring? Or was it because I used the wrong quenchant for this steel?

[MattBower]

Or why didn't this piece get as hard as I expected? Is it because I used a too-slow quenchant, because the carbon is low, because I over-normalized, or because it needs to soak for a while at the austenitizng temperature in order to get the carbon fully into solution? And so on, and so forth.

Knowing what you have helps eliminate a lot of variables.

[BlissStreet]

I don't know anything about steel prices in South Africa, but I can get five feet of 1/4"x1-1/2" 1080 from Admiral Steel for around $20,

I know it sounds silly, but it's not about the money. I just feel guilty screwing up perfectly good steel. I'm not to sort to be cheap, but I think that I need 4-5 more springs of practice before I'm ready to start out on new stock. Also, I'd rather not start accumulating more stuff right before an impending international move.

When I have the skills to translate my ideas to the anvil, then I'm certainly going to look into solid stock supplies.

[BlissStreet]

And since we are having a good discussion, I thought I'd ask:

When you cook and bake in a convection oven, you have to adjust your temp to accommodate the moving air. Usually, you decrease the temp by 50 degrees F. Ex: in a convection oven you bake at 300 rather then 350 degrees to get the same results. I know it sounds silly, but if you are tempering in a convection oven do you do that same with the temperature compared to a still oven?

[MattBower]

I don't know. Probably. Ultimately the thing to do is test some post-tempering blades to see if you need to adjust your process. The temperature is less important than the effect, especially since you're using mystery steel.

One thing I can tell you is that home oven temperatures are not very stable; they can swing pretty wildly. My best advice on dealing with that is to preheat an aluminum roaster pan full of sand, and bury the blade in that for tempering. The thermal mass of the sand will tend to even out the temperature swings.

[Steve Sells]

Use a temper color chart. I use the home gas oven. I set the temps close to where I know it was the last time I did that steel, BUT I have the blade polished and shiny so I can read the color of the oxides to verify what temp it was really at. The Oxides do not lie, but we can misread them a bit.

[pkrankow]

A convection oven uses a fan to circulate the heated air. This changes the heat transfer rate, increasing it greatly. This increase in rate is why when cooking you need to reduce the temperature so the heat can penetrate the food without burning. With a knife that you are tempering it should eliminate hot and cold spots creating a more even result (remember to accommodate for radiant heat effects from the elements if necessary) but the final temperature is still the same, so the oven setting would be the same.

Phil