Stubborn leaf springs

[Luke Pickering]

Morning.  I posted last week about a set of leaf springs I picked up for cheap.  There is a massive amount of steel here for me to practice with but I am struggling to get it play ball. It just doesn't move very much under the hammer.

I was hoping to use it to make kitchen knives but I just don't see myself being able to thin it out in a sensible amount of time.  The leaves are about 10mm thick and very stubborn.  I also suspect I am doing a lot wrong though.

I am trying to draw the material, striking just off the edge of the anvil at around 45 degrees.

I am heating to orange - should this be yellow?

I am only using a 2.5lb hammer as I don;t have anything larger.  I am reluctant to go out and buy a 4lb hammer if the issue is due to my technique.  On the other hand, I would be willing to buy one if it is likely to help.  I would have thought proper technique first, hammer second?

Any tips would be great

[JHCC]

4 minutes ago, Luke Pickering said:

I would have thought proper technique first, hammer second?

Absolutely. You might want to start with some smaller stock or to practice basic smithing skills (i.e., not knifemaking) on mild steel to get the mechanics of drawing out solidly in your muscle memory before you tackle the tougher stuff. 

The good news is that the spring steel isn't going to go bad while it waits for you to develop your skills.

[jcornell]

Get the steel hotter.

 

[Buzzkill]

I agree with both of them, but with a qualifier.  For me it seems there is a point where leaf springs do move better under the hammer.  To my eye it's high orange/almost yellow.  However, if you are using solid fuel it's very easy to burn the steel if you go much hotter than that.  If you go too hot you'll probably get some combination of the sparkler effect, or more likely you'll strike it and it breaks off unexpectedly.  The thinner the piece the easier it is to have this happen.  Some of the coil spring I've used is particularly susceptible to this, which is one of the reasons I've gone mainly to propane.

[Gergely]

Try to cut the leafspring into stripes - say 20mm wide stripes for starter and about 400 mm long. Heats up faster and it's way easier to move than a 80mm wide piece. 

You can do pretty big harm to any suitable piece of steel with a 2,5 pound hammer  

And if this brings you any relief: I started with the "same kind" of leaf spring when I started forging, and it was very tough on me too. Nowadays I can move spring steel with ease compared to how it went back then. (True that I use power hammer for most of my works  )

Happy hammering!

Gergely

[Jackdawg]

Just be careful if you go to a bigger hammer, bigger hammers and undeveloped technique on similar steel to what you describe stuffed my elbow for 6 months.

[Kozzy]

You might do a simple test to make yourself feel better about it--but it'll take the cost (or borrow) of a proper sledge.  Heat a piece, do a 2 hand heavy sledge hit on it and see how it moves.  50 years ago this would have been SOP because every smith had a helper to pound while they held the part.  

You'll likely find that under that kind of force it moves remarkably well.  Even though control is poorer, you can often do in 5 minutes what it'd take 5 hours to do with lesser hammers. Then you can move to your 2.5 lb for finishing.

Making a hold-fast first can help if you go to the two-handed sledge (or ask a friend to help for a few minutes to hold the part).  As was also said, work the metal quite hot:  Plain old red isn't quite going to cut it.

I just fought something similar before breaking out the sledge...and cursed the hours I wasted prior.  I am however, quite practiced with a heavy sledge so I can't say how tough control will actually be for someone with less sledge-time in over their life.

[Irondragon Forge ClayWorks]

One thing I've learned with thick leaf springs is to let the metal soak in the fire allowing the heat to get all the way through and yes orange heat is just barely adequate. Like Buzzkill says, closer to yellow works for me.

[Frosty]

Ahhhhh, leaf springs. They're so close to the shape want to make they're very tempting. Unfortunately it's harder to forge blades from leaf than coil spring. Seriously it's MUCH easier to get a nice blade profile starting with a round bar than strap stock.

That's not saying I don't have a few hundred lbs. of leaf spring. 

Frosty The Lucky.

 

[Irondragon Forge ClayWorks]

Some of the best knives I have made were from old buggy springs. They are just about the right thickness for knives and the ones I have spark test as high carbon and harden well then temper back beautifully. A friend of mine gave me about 20 when he was cleaning up the back of his shop that were buried. Played havoc with his rotor-tiller.

[Frosty]

Those would be high carbon low alloy think O-1 neighborhood.

Frosty The Lucky.