How to Avoid Stress Cracks when Forging a Leaf

[ofafeather]

Hi, All,

I've been working on forging items with leaf or spade shape finials, such as hooks or key chains. I seem to always get cracking near where the finial meets the stem. I usually start my tapering the end then necking in to isolate the material for the finial. I have tried forging the finial next then drawing down the stem material. I have also tried drawing down the stem first then forging the leaf. I am getting cracks both ways. Can anyone give me an idea of how to avoid this?

Thanks!

Eric

[thecelticforge]

Keep the leaf hot.

[MRobb]

Sounds like you are continuing to forge after it has lost too much heat. keep it hot. Good luck.


Mitch

[Dodge]

Eric,
Much depends on the metal. But as a quick answer, maybe forging too cold or the "neck" could be too sharp. What type of steel is it? How do you neck down? Edge of anvil? Is it radiused sufficiently? Pictures would be helpful
Scott

[Dodge]

WOW!! That was quik But it seem that we all tend to agree LOL :P

[edge9001]

I had a similar problem with some of my knives when I first started, It seemed to me I was hammering after it got to cold. when the leaf gets too cold for thype of material your using, apply more heat.

[ofafeather]

Thanks for the quick replies! I'm using mild steel and necking in on a very worn anvil edge from 2 sides 90 degrees apart. The neck seems to be fine as I work on the leaf or draw down the stem. It's only has I approach completion that I find there are some cracks right at the join. Typically this area is worked HOT and first so I'm inclined to think that the stress somehow comes when I'm working the other areas. Could that be? When I get home I'll take a picture of the one I made yesterday.

[Rich Hale]

Not to sound like I am on your case but quite simply it just may be that you need to make a few hundred of these and then you will wonder how it ever seemed difficult. Could it be that the underlying problem here is lack of forge time? By that I mean do you have the basics down really sound? Do you have a routine that works for you every time you pull hot steel from the fire? Think about wot you do at that point and see if there is any hesitation or delay in hitting the steel accuratly to move metal in exactly the way you want it to move.
One of the most difficult tasks is to work with small stock while you are trying to develop muscle memory and efficiency while forging. Larger stock holds heat longer and allows you to find success earlier in the curve. And yes that does take more work but that is really a good way to learn how metal moves at heat under a hammer and how you can use your hammer and anvil in maybe different ways to do different things. One thing I always try and remember is thata practice may not improve your skills, only perfect practice can do that. Think about that a minute; If yoiu are doing something incorrectly you may be able to one day get it done the way you want. But can that kind of forging allow you to move ahead in the art? And If you develop good skills that may take a while to learn those skills carry on into anything you do in the future. Read all of the posts you can find in here and keep a mental note of wot kind of problems lots of folks are having. How many can you find that are based on limited forging skills? The more you read the more I suxpect you will see wot I am refering to. Good skills apply to all forgings. As well as poor skills do. If wot I am saying offends you and you feel that you have all the abilities and practice you need then let this live for others to see and perhaps it will be of benefit to them.. and have fun

[bigfootnampa]

I don't want to distract you from the other answers but I think another thing that may be a problem here is the grain growth and the pendulum effect on the thin part of the stem. As you work the rest of the leaf you are heating and reheating the thin stem area without working it. Then the heavier main part of the leaf is being worked and you are sort of breaking the stem accidentally as you would if you had purposefully bent it back and forth until it broke off. This sort of problem does not occur when you are making leaves in one or two heats (as Hofi and some others will do). I have run into it when I worked a long bar AFTER having forged a leaf on one end of it (I should have worked the bar FIRST and then made the leaf). The thin stem is easily heated and very soft at heat... thus easily damaged. Excess grain growth (which leads to weakened areas) can also occur if the stem is repeatedly heated without being forged to break up the steadily enlarging grain. That having been said the earlier posters are probably right that you are working the piece too cold. Just knowing about all these complex factors at work as you hammer your simple leaf WILL (surprisingly) help you to sort out the trouble and (with practice) eliminate it.

One more possibility is that you may be OVERheating the stem. If you see any sparks as you remove your leaf from the fire this is likely to be the culprit. Even very slight burning can lead to serious weakness in a small section like a leaf stem. Because the stem is quite thin it is very easy to overheat and less experienced smiths might not recognize the warning signs.

Oops... I see one more thing to watch for... are you quenching your steel?

[ofafeather]

And If you develop good skills that may take a while to learn those skills carry on into anything you do in the future.

Rich, you make good points. I take no offense at and I certainly can use more forge time. I believe though, that there is a combination of factors that cause the problem, as is often the case. I can tell you that the steel is worked HOT. I believe my issue is more related to BigfootNampa's description than to cold steel. The pendulum effect is what I was trying to describe but could not think of the words. I had heard Brian Brazeal mention the same thing. I think if I were able to forge in less heats it would minimize the problem.

I don't believe that I am overheating the stem. It is possible, but I haven't seen any part of it go past orange. It is getting heated many times, though, without being forged.

Nampa, you mention quenching...is that good or bad? I only really quench when I need to. Should I quench parts that I am not going to be working?

I'll certainly be working on making more, hopefully in less heats. Just looking to see how I can improve things.

Thanks!

[ThomasPowers]

Are you really paying extra to get 1018/1020 or are you using A36---what you usually get at a steelyard if you ask for mild---and it's not really mild!

[ofafeather]

Are you really paying extra to get 1018/1020 or are you using A36---what you usually get at a steelyard if you ask for mild---and it's not really mild!

Definitely hot rolled, except for the occasional cold rolled.

[bigfootnampa]

I think quenching can lead to a lot of problems. I tend to do it very little (except when heat treating). When I do quench it is usually my handle end and BLACK hot... just starting to get uncomfortable to hold.

Okay I think you have narrowed the problem down now what to do to fix it? Working faster and using less heats will help. Leaving the stem a little thicker and giving it a few gentle hammer whacks as you forge along is likely to help. Quenching the stem before working the rest of the leaf is a useful possibility... maybe with a wet swab... the grain growth is less likely when the part cools quickly. A tight fitting tong that is kept cool and used to grasp the stem as it comes from the fire perhaps. A little work on the stem will help break up the grain growth mechanically and also cool the stem from hammer and anvil contact. Overall I would say try to work faster and forming the stem in small steps throughout the forging process would be good strategies for you. That is the best things I can think of now anyway.

[Larry H]

When you make your first 50 one heat leaves you will understand

[Dave Hammer]

I agree that the more you make the easier it will get.

I used to have the same problem you are describing. After about fifty or a hundred leaves, I started to leave the stem about 50% thicker (than the final cross section) at it's junction with the body of the leaf until the leaf was almost finished. Also, I forge the stem as a tapered square bar, not rounding it at all till the leaf body is done. THEN I forge the stem to the shape/size I want. Works every time for me. The only time I get a cold shut there now is when I'm not paying enough attention and get the stem too small to soon.

[Frank Turley]

Alfred Habermann showed the leaf form when he came to the States from Czechoslovakia in the early 1980"s. I assume you're doing his style, pointing and necking over the far radius of the anvil. To get proper leaf width, the pointed taper should be the same angle as a sharpened pencil. The two 90º shoulders should begin immediately behind your taper, into native material. If you're not too shy with the hammer blows, you wil get a lump forming below the anvil edge in one or two heats depending on stock size. The stem on the anvil face will be square in cross section and thin. When you turn it part way over, the stem will be on the diamond (corner up) and the lump facing upwards. Take a heat taking care not to burn the stem and flatten the leaf at the anvil face middle. I will often leave the stem square on the finished piece; it has a nice look. The leaf may be slightly thicker at its point than on its lobes, but that is OK. Then you give your work an attitude by curving the lobes, the tip, and the stem.

Don't let the lump flop back and forth at a black heat. Don't straighten any bending at a black heat.

http://www.turleyforge.com Granddaddy of Blacksmith Schools

[fciron]

Oh, this is a new thread. I posted about this in another leaf thread a while back.

To expand on what Frank Turley just said, there is actually a heat range just below incandescent where the steel is actually more brittle than when it is room temperature. I actually try to keep that shoulder area hot (by which I mean glowing, preferably orange) while spreading and shaping the leaf so that it will have the plasticity to absorb the shocks.

[ofafeather]

Thanks, All,

Hopefully I'll get a chance to forge a bit today and try some things out. I'll let you know how I fare over my next several attempts.

[Braedon]

i make both the leaf keychains, and leaf necklaces i dunno what i am doing different than you but if this vid helps then cool,,My link

[Braedon]

lol that didn't work out so well http://www.youtube.com/watch?v=k3sc0raxRPQ