Will case hardening "stiffen" a bracket
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    Default Will case hardening "stiffen" a bracket

    I have some brackets that are not quite stiff enough to do what I want to do with them. The steel used to make them is very questionable but probably the cheapest that could possibly be purchased. My question is would case hardening them stiffen them up a bit. They are quite small and I don't want to make new ones. Case hardening would be quite simple using Kasenite. This is kind of a general question as well since there have been numerous occasions where I have had brackets, small truss rods etc. that I would like to make a little stiffer. I am not trying to make gold out of lead here I just want to make them somewhat serviceable. Thanks for any replies in advance.

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    Hardening something will not change it's "stiffness", but only improve its resistance to plastic deformation.
    See here: Young's modulus - Wikipedia, the free encyclopedia

    Benta

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    Thanks Benta. I was afraid of that. I do a lot of case hardening for pivot pins on backhoes and tractor buckets but I have never really tried it on something I was trying to stiffen, only for wear resistance. I appreciate your input.

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    Most junkyard steel is only A36 anyway, and just plain wont get very hard. Unless you dont want it to- then, there will be some weird amounts of "allowable" stuff in the melt that makes it get TOO hard.

    Bigger, thicker brackets are probably in your future.

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    Get it red hot, then soak it in a bucket full of ground up "little blue pills" (which for the life of me I can't remember the name of right now!!!!) It claims to make everything hard.

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    Quote Originally Posted by JoeE. View Post
    Get it red hot, then soak it in a bucket full of ground up "little blue pills" (which for the life of me I can't remember the name of right now!!!!) It claims to make everything hard.
    But only for 4 hours. Otherwise something is wrong and you have to call a doctor.

    -DU-

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    pretty sure he wants his brackets to stay hard well after the ol is done
    haha
    seriously though as Mr.Ries so succinctly put it, i see bigger brackets in your future

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    Quote Originally Posted by JoeE. View Post
    Get it red hot, then soak it in a bucket full of ground up "little blue pills" (which for the life of me I can't remember the name of right now!!!!) It claims to make everything hard.
    Viagra is only for people.

    Tom

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    Question for the engineers - If the modulus of elasticity is the same for all steels, and heat treating (hardening) doesn't change it, Why is a hardened pry bar stiffer than a soft one? Wouldn't the higher tensile and yield strength make his brackets more resistant to flex? Empirical experience and the logic conflict for me, I've been looking for an explanation for this.

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    Quote Originally Posted by Mud View Post
    Question for the engineers - If the modulus of elasticity is the same for all steels, and heat treating (hardening) doesn't change it, Why is a hardened pry bar stiffer than a soft one? Wouldn't the higher tensile and yield strength make his brackets more resistant to flex? Empirical experience and the logic conflict for me, I've been looking for an explanation for this.
    It's the difference between elasticity and yield strength.

    A plain steel and a hardened steel pry bar would bend/deflect about the same. But the soft steel bar would ultimately bend and take a permanent set with less force applied.

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    Got it. The hard bar will flex the same up to the point where the soft bar is ready to yield, and continue to flex and still return. So it seems stiffer.


    ...........

    But - I have a piece of 1/4" diameter rod about 18" long, non magnetic, tests at about 2 Rc, seems to be stainless steel. I can't flex it much holding it in my hands and pushing with my thumbs. The same size of 1018 I can spring quite a bit. What is the difference there? I'm trying to chose a pushrod material for a customer, to duplicate his sample.

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    Thanks for the replies guys. I already know about the little blue pills however. I have to take a half of one to keep from peeing on my shoes.

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    Okay I'm going to stick my neck out here and display my ignorance. I have a bunch of steel here in the shop. I have some that I know what it is like A1. O1 4140 etc. I also have a ton of mystery steel. Some of it is very stiff. Think push rod or valve stem. Some other is quite bendy. My question is does the chemical makeup of the steel determine the stiffness? I am not talking about hardness like in the Rockwell scale or for wear resistance but how bendy it is. Is most of the stiffness due to heat treating, chemical makeup or a combination of both? If it is heat treating then I would think I could heat up my brackets and quench them or something. I know this would not make them any harder without case hardening because there isn't enough carbon in the steel, Opinions?

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    If they are sheet metal then adding some indents along the fold can help: Sheet metal work stiffening bends | V and F Sheet Metal. If the brackets are machined from soft steel it might be possible to do the same thing.

    I'm not a metallurgist but wonder if the material isn't annealed and needs to be heated and quenched to bring it to its spec'd characteristics.

    Cheers,

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    To the OP, heat treating your brackets with Cherry Red, Kasenite etc may well make them more serviceable depending on how you are using them. Try this quick experiment.

    Heat treat 2" of the end of a piece of 1" X .125" mild steel flat, keep the heat on it for 3 minutes or so. Put the flat in the vice, leave 1" of the untreated end sticking out and bend it over 90° with a hammer. No trouble at all doing that. Now try hammering over 1" of the treated end.....

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    If your brackets are made of stamped sheet metal,you will actually remove any work hardening that bending and forming them put into the brackets when you heat them up. A few thousanths of case hardening is not going to compensate for annealing the brackets,and they will come out weaker than when you started. Weld in a gusset to strengthen them.

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    +2 on the gusset, haven't ever seen anything worthy at lowes or HD but there are places like this that have tons of variety and cheap, for less than your time is worth.
    gussets
    on a related note, i save a bunch of my 'triangular shaped' cut off's from the band saw, keep them in a wall bin in the fab area with the other builders hardware type stuff. i go to that bin regularly for a random gusset.

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    A simple thought experiment that will help clarify these concepts to the uninitiated:

    Take a 1/4" bar of A2 and harden it
    Take another 1/4" bar of A2 and leave it soft
    And take a 1/4" bar of dead soft mild steel.

    all the same length...

    in three vices on your work bench.

    Hang the same amount of weight at the end of all three and they will all droop the same distance. This is, for all intents and purposes, the same for all steel regardless of hardness, heat treat or chemistry.

    Add a little more weight on them and they all flex a little more.

    The amount of deflection is proportional to the amount of weight. Steel is a linear elastic material and this is elastic deformation. That's lucky, or springs for scales would be very tricky.

    However, as you continue to add weight you will eventually reach a point where the softer steel yields and begins to deflect more than the harder steel. This is plastic deformation, meaning it won't come back fully straight after the weight is removed.

    All steel flexs the same within the limits of elastic deformation. Once you start permanently bending things the harder steel appears stiffer.

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    Thanks NTM and all the others who have replied. I'm really not worried about these brackets. Yes it would be nice if I could stiffen them up a bit but gussets would of course solve the problem. My question was more or less one of those "what the heck" kind of questions that keep you up at night....or in my case allow you to go to sleep. ( I'm one of those people who lie there and design breech blocks for artillery until I fall asleep. I'm sure others have their favorites) .Thanks again.

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    The uniformity of stiffness is an article of faith, but here is my real world experience. It was copper, not steel, but the rules are supposed to be similar. The huge valves that control the inflow of Mississippi into the Riverview water works are operated by motors which in turn are controlled by contacts. The contactors are housed in water tight boxes next to the valves. Sealed up like that, the contactors looked new except that decades of turning St. Louis' water on and off had eroded the contact surfaces. The contactors were long out of production, so maintenance people were faced with replacing the complete units. They asked me to make replacement contacts, which I did, dime sized silver disks silver brazed onto about .070" copper strips. I cut out the strips, brazed on the contacts and was ready to silver plate them when I realized that the heat had annealed the copper and they bent with just the light spring pressure in the units. Faced with scrapping the whole lot, I tried bead blasting the copper to work harden it. That neatly solved the problem and St. Louis gets drinking water.

    I don't care what semantic games you play, the fact is that peening made them a lot harder to bend.

    Bill


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