Type of steel used in leaf springs

[flyguy8555]

I've searched the forums, and haven't had much real luck finding out what type of steel leaf springs are made out of. I realize that there may be more than one type of steel used for leaf springs - I'm just curious as to the carbon content in general. I was "gifted" with a pile of truck springs, and I'm planning on having a friend with a plasma cutter (a good friend to have indeed) cut them up into usable pieces for forging knifes.

[Rashelle]

The spring shop I get some of my 4140 and 5160 from makes round springs out of 4140 and leaf springs from 5160. That is that shop. Other shops may have other steels. Junk yard steels are mystery steels unless you know where the steel came from in which case it isn't a junk yard steel. Vehicle manufacturers may have tried different alloys in the past. That said you might have 5160 for the leaf springs.

 

Rashelle

[jmccustomknives]

Most modern car, truck and simi springs are 5160 or a version there of.  I'm told that some heavy duty springs can be 6150 but I haven't run across it yet.  I also spoke with a gentleman who was in the steel industry back in the late '80's and he said GM used 52100 on their trucks.  I did obtain a set of springs from that vintage, I didn't have an analysis done but they worked like 5160.

[lupiphile]

Almost, invariably 5160. It's one of the very few reliable "known" steels you can easily, and constantly identify and purchase  from the scrap yard. I use it for about 80% of all my tool making. If your used to working 5160 and you come across some 6150 you will quickly notice the difference , it's much harder to work,. It's akin to 4150, but a touch tougher. It also wont let you get away with murder the way 5160 will (overheating, working it hard under the hammer waaaaay to cold, sloppy heat treating, i.e. the "look ma, no oil !" approach to hardening ect.) I've been told some really old leaf springs were 1080 or some such, but with a trip to the scrapyard 2 times a month for the last 6 years I've yet to find one. Take care, Matt 

[Frank Turley]

In the AISI/SAE numbering system for steels, the last two digits in a four number ID indicate the carbon content. For example, the 60 in 5160 means 60/100ths of one percent carbon content.

[ThomasPowers]

In 33 years of smithing I have come across *1* low carbon strain hardened leafspring so the oddball ones do exist even if they are not common.

[flyguy8555]

Thanks guys! I appreciate the intel, as always.

[Crunch]

I know this is an old thread but ... I have some old leaf springs from a school bus, and I want to make a heavy "timber framing" chisel 1-1/2" wide ... assuming that my springs are 5160, would this steel be good for making a timber framing wood chisel?

To dig a little deeper...would 5160 be appropriate for:

- the body of the chisel?

- the cutting edge of the chisel?

Or would I be better off using a mild(er) steel for the body and possibly a different steel (say 1095) for the cutting edge? (I'm thinking I would like to use fairly vanilla steels for this since I am such a novice.)

(Also, if it matters, I may try to get a machinist friend to make the "socket" portion of the chisel on his lathe, and then I will likely TIG weld that to the chisel body before forging, since I don't have any mandrels or swage blocks/dies for making the tapered socket, and since I'm far better at tigging than at blacksmithing...)

Thank you for any advice.

(By the way, for anyone interested, I found a very informative blacksmith on Youtube who goes by the username "Black Bear Forge" ... I don't know whether he is a member here, but I've learned a lot from his videos.)

[JHCC]

First of all, Black Bear Forge is one of the better blacksmithing channels on YouTube, as I think pretty much everyone here would agree. Informative, well-produced, and well worth your time.

As for making a timber framing chisel from a leaf spring: yes, 5160 is entirely appropriate for this usage. It will harden enough to take a sharp edge, and it will be tough enough to withstand the pounding from your mallet. 

Steeling the edge (welding a high-carbon edge on a low-carbon body) would be a whole lot of work for no significant benefit. Don't bother.

TIG welding -- any kind of arc welding -- is going to increase the risk of cracking in the heat affected zone. Make sure you do the appropriate pre- and post-weld heating.

If your machinist friend is going to be making you anything, why not have him turn a cone mandrel so you can forge the socket yourself?

[Frosty]

Timber or log framing? Oh yeah,  spring steal makes excellent wood slicks and other log/timber framing tools. If you split the socket so it sandwiches the blade you can rivet them together. If the blade bottoms out in the socket's slit it won't go anywhere and it's a low stress join.

Do any welding BEFORE you heat treat the blade though not necessarily before you forge it. Forging sets up stresses in the steal and not necessarily where you're hitting it with the hammer. Welding sets up stresses too so you want to do this so they don't multiply each other. 

Forge, normalize, weld on the socket rough grind, normalize and heat treat it all at once. 

If you aren't panning on  hitting it with a mallet you can rivet a salvaged shovel socket to the blade and use a shovel handle. This would be a slick. We used to use slicks to clean up notches and dovetails too, they're versatile if you make them stout enough.

Frosty The Lucky.

[George N. M.]

Before I did anything with the particular spring steel that you have I would harden and temper a test piece (a "coupon") to make sure that your particular steel will harden and temper the way ytou want to.  Some spring steels are odd alloys which do not heat treat well in  home shop.  I have had some significant failures over the years.  Generally, the older the spring the more straight forward its heat treating.  I made some nice knives out of a 19th century buck board seat spring.

"By hammer and hand all arts do stand."

[Crunch]

This is great advice, everyone, thank you all very much. I didn't even know what questions to ask, apparently, but you guys answered several I didn't even know to ask!

I really appreciate your help, and will let you folks know how I make out.

Best regards to all, and thanks again,

Jeff

[Frosty]

Thanks George, I forgot about evaluating the spring stock and it's really important. 

Iforge has an extensive knife making section I HIGHLY recommend you spend some time going through it to get an idea of what to expect and such.

Frosty The Lucky.