Well said Matthew!   Even as 'one of the blacksmiths" I learned quite a
bit, especially the upper limits of carbon content.

Speaking of leaf springs, couple Januarys ago a buddy of mine came up to
forge leaf hinges for his Teardrop trailer. Big Round door like a hobbit
hole so he was looking for a forged look. Not thinking about it, we used a
bunch of leaf spring I had laying around, and maybe leaves out of eight in
I started suggested we punch the holes hot, suddenly thinking about the
material we were using.

'no, not yet' said Phil, still a little unsure of where on the trailer and
door the bolts for the hinges were going to go.

https://www.flickr.com/photos/10735775@N.../51105601474/

'why don't we just punch some of the holes, maybe the ones on the ends of
the leaves' thinking this stuff was going to be hard to drill, especially
in phil's far more wood oriented shop.

No dice, finished all 4 hinges, even had time to play around with some
angle iron sculpture.

About a month later, I get an email picturing a pile of broken, burned and
just rounded off carbide drill bits, along with a smoked cordless drill.

the only text 'next time we'll punch the holes'

Michael

On Fri, Apr 9, 2021 at 1:15 PM Matthew Groves 
wrote:

> From Gary
> > Scott---
> >   In practical terms, is there a difference between truck spring steel
> and tool steel? Serious question!
> >
>
>
> From Scott
> > OTS, old truck spring, would make a dandy froe.
>
>
> >  But forged, hardened and tempered to spring temper it would make a
> > great froe!
>
>
> There are a dozen other metallurgists and blacksmiths on the list that
> could (and I hope do) say it better than I.
>
> Here it goes.
>
> 1. There’s nothing wrong with making a froe from a truck spring, but it’s
> more about convenient starting shape than it is about metal.
>
> 2. Not to disagree too heavily with Scott, but froes have been made out of
> soft (ish) steel for quite a while and they work just great. No need for
> hardening or tempering. No need for edge retention or anything else that
> would steer a person toward some steel alloy capable of such. Mild steel,
> the kind that’s plentiful is usually either 1018 or 1020 or A36. The 1018
> and 1020 describe a steel that has .18 or .20 percent of carbon in it’s
> formula. A36 doesn’t describe a steel composition, but instead sets minimum
> performance standards for that steel.
>
> 3. Old truck springs usually get the label of 5160 steel, which again is a
> composition label that among other things includes .60 percent carbon. It’s
> often referred to as 60 “points” of carbon.
>
> 1018 has .18 percent carbon, so 18 “points”. It is not hardenable, yes
> even with the galoot superquench.
>
> Lots of automotive parts use medium carbon steels. These have enough
> carbon to be hardenable, but that hardness depends on how much carbon there
> is.
>
> Axles and tie rods are often 4140 steel (40 “points”, you now get it) and
> can get hard. Spring is often 5160, and it gets harder than 4140 at it’s
> hardest.
>
> “High carbon” steels are up in the 80 and 90 and 100 and 110 “point” range.
>
> 4. Here’s two things most non-metallurgists need to know about steel and
> strength.
>
> a) ALL steels have very similar modulus of elasticity, which means that if
> you apply a force that makes them bend, they all bend about the same amount
> given the same amount of force. This is called ELASTIC Deformation.
>
> We’ve all seen steel get bent by a force, but spring back when that force
> is removed. And we’ve all seen steel get bent to an extent that when the
> force is removed, even though it springs back some, there is some permanent
> bend introduce. This is called PLASTIC Deformation.
>
> b) higher strength steels, even though they have the same amount of
> ELASTIC deformation as low carbon steels, can withstand a LOT more force
> before they PLASTICALLY deform. This is why spring applications (where you
> WANT it to return to form) involve alloys of at least a medium carbon steel.
>
> 5. The medium and higher carbon steels do not need to be hardened in order
> to have this higher elastic deformation limit. A froe made from truck
> spring (5160) will be tougher just because it’s 5160, even when you don’t
> harden or temper it. It’s automatically a superior froe, and there’s no
> need to proceed with those steps.
>
> 6. A hardened steel is virtually always a more brittle steel. That’s the
> tradeoff. So chisels aiming for rockwell 62 for that super keen edge are
> also gonna be brittle. This is a generalization. Fancy alloys are always
> coming down the pike. A froe needs to be tough way more than it needs to be
> hard. It’s subject to many forces form the handle and the froe club. Also
> if it DOES fail, you’d much rather it bend than snap.
>
> 7. The upper limit for carbon that contributes to hardenability is in the
> range of 1.3%. Past that, and the carbon does things that reduce the
> hardenability. Cast iron has 2 to 4% carbon, for instance. Not hardenable
> AND brittle!
>
> 8. There are tons of alloys out there and each is like a recipe with
> different methods of achieving it’s max softness and hardness. Sometimes
> designated by the speed of it’s quench. O1 and O2 are very forgiving alloys
> that harden fine in Oil, hence the O. W1 and W2 are alloys that need the
> speed a Water quench provides, hence the W. A1 and A2 are air quenching
> alloys, as are D2, L2, A33, H13, and S7.
>
> Obviously, I’m leaving a lot out, but these are basics.
>
>
> Here’s the short version: You CAN make a froe out of truck spring, but
> mild steel works fine and hammers much easier. Don’t bother hardening or
> tempering.
>
>
> A metallurgist in another life,
> Matthew Groves
> Springfield, MO
>
>
> 
>
>
>

-- 
Michael