Annealing a Leaf Spring

[Nolan]

So I've got a fairly good-looking leaf spring that I plan on making two knives out of. When I set out to cut the thing with a hacksaw, I became afraid that I'd damage the saw because it was so stinkin' hard. So I come to a question: Will I be able to forge it without annealing first, or do I need to? If I need to anneal, what would be the best way (air-cool/sand-cool, how many times, etc.)?

 

Thanks

Edited July 11, 2012 by Nolan

[Alan Longmire]

You can certainly forge it without annealing first. You can even cut it with a hacksaw as long as you've got good blades. If you do decide you need to anneal it for sawing it up first use a bucket of vermiculite. 5160 will air-harden a bit. 9260 will also, but not as badly. Get the whole thing up to a nice bright orange and immediately stick it in the vermiculite so it's completely covered. It'll stay hot for several hours depending on how big it is, but overnight is not unusual.

 

All that said, I rarely anneal leaf spring before forging. It doesn't need it. It does need multiple normalizations afterwards, of course.

 

Edit to add: You will want it annealed if you're going to drill holes in the tang, it's hard on drills.

Edited July 11, 2012 by Alan Longmire

[Jon Stormm]

If you need vermiculite, you can find it on Amazon.com

[Al Massey]

If you need vermiculite, you can find it on Amazon.com

Heck, iirc you can get it at any garden-supply place.

[Jon Stormm]

Thats what people keep telling me, but I kept stopping into the Lowes and Homedepots around my house and none of them carried it and the employees had no clue what I was talking about. The only place bearby that I could find was a small garden shop, mom and pop style, but they keep weird hours. They're only open while I'm at work.

 

 

[dragoncutlery]

at lowes and depot check with there building supply desk it is used to insulate cinder block walls and when i worked at menards they had big bags in stock all the time the others may have to order it but at least there's a chance and walmart has a slim chance as well

[Jon Stormm]

In the end, I just found it was easier to order on Amazon. I just hit the one click one day delivery and buy cob the next day it's sitting at the front door of my shop and I didn't have to waste the gas of driving all over town trying to chase down a bag. :-)

[Doug Lester]

Of course an alternate method would be to heat the areas that you want to cut through with a torch and draw the temper back further. Another would be to austinize that area with something like a rosebud burner on an acetylene torch and allowing it to air cool. Neither method will get it as soft as annealing but they may get the steel soft enough to cut more easily with a hack saw.

 

Doug

[Nolan]

Of course an alternate method would be to heat the areas that you want to cut through with a torch and draw the temper back further. Another would be to austinize that area with something like a rosebud burner on an acetylene torch and allowing it to air cool. Neither method will get it as soft as annealing but they may get the steel soft enough to cut more easily with a hack saw.

 

Hmm.. That's a good idea. I'll try that.

 

Thanks!

[B. Norris]

You can cut your leaf spring with an abrasive cutoff wheel mounted on an angle grinder, it is much faster than a hacksaw and the abrasive cares little how hard the steel is. Another method is to just heat the leaf spring up in the forge, hot cut a chunk off, and forge your knife from there. Annealing will be more successful for you, especially with 5160, if you heat up another mass of metal and bury it in the vermiculite with your leaf spring. You want the steel to cool as slowly as possible, so adding more mass (and heat) helps to achieve that.

 

~Bruce~

[Alan Longmire]

Another would be to austinize that area with something like a rosebud burner on an acetylene torch and allowing it to air cool.

 

Of course, if it is 5160 it will probably harden a bit in air...

 

A high temper can work, I do that for tough holes. Polish the steel a bit and hit it with a propane torch. It will run through the temper colors. Go as hot as propane will get it, which will be around 8-900 degrees F, and allow to cool without quenching. You don't want to get it above 1500 degrees.

 

I cut new leaf spring stock in my bandsaw with no problems, but I'd hate to split one 32" longways with a hacksaw for sure.

[Nolan]

Got it cut...man that's hard. Now I have no problem believing that bullets bounce right off leaf springs.

[Doug Lester]

If you really want to do it the hard way you could split leaf springs the way that Tim Lively did it on the Hood's Woods knife making video. He made a groove with a cold cutter down the length of the spring section, he had cut it across the width first, then austinized the piece and ran water down the groove to harden that section. Then he just gave it a smack with a hammer to break it. I've cut work off a section of bar this way and it is actually a bit easier and faster than cooling the steel then clamping it up in the vice and cutting with a hack saw. I did it hot cutting, however. Think to come of it, Tim Lively might have too; whatever, it was a three man job for the leaf spring. I'd have to dig out the vid and check. Just remember to normalize the cut ends to remove the untempered martensite. If you want fast and easy, use an angle grinder with a cutting disc, though you might go through a few disc breaking down leaf springs.

 

Doug

Edited July 13, 2012 by Doug Lester