2017 January 10    Tech   Metal & Shop

Introduction


This article is about a very simple lamp bracket that I'm working on.  The starting material was some round stock that I think is mild steel, or possibly wrought iron. 

Working with hot metal can be dangerous.  Improper heat-treating of metal can be dangerous.  Please read the Disclaimer, and make sure you wear proper safety gear when doing any type of metalworking.



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In This Article


Scrap Iron

Lamp Bracket

Mild Steel?

Testing Unknown Iron

Salvaging The Bracket

Conclusion




Scrap Iron


It's great to have neatly-arranged racks of steel, where every alloy is known.  But right now, many of us just have a heap of rusty junk of unknown type.  With junkyard steels, you sort of have to figure out what's there as you go along.

I got hold of some round stock that looked as if a tornado had hit it.  It was multiple feet long and all twisted up like a pretzel.  This was at least 1/2" diameter, as I remember.  (I'll have to check again.)  The ends were threaded.  It looked old, maybe a hundred years or something.  And it had been sitting outside for a long time.

At first I thought 1890's steel-- or whenever it was from-- must have a decent amount of carbon content.  But this steel bent very easily.  Unfortunately, I didn't think about the carbon content until after I made a few things out of it. 

One of them was a lamp bracket, which we'll get to soon.


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Lamp Bracket


So one day I decided to make a very simple bracket for hanging a light fixture.

The round stock was only about 1/2" diameter.  Even so, there were times when a 2.5-lb hammer seemed almost too light.  Later I tried a 4-lb hammer and it worked better.  I think the reason was that my heat source wasn't getting the iron much beyond red heat, and it was also cooling down too fast.

The anvil for this project was a piece of rail that I picked up from a junk shop.  I have access to a "real" anvil that I could have used for this project, but I'm just messing around at this stage;  it's not production or even serious art (yet!!).  The track anvil is there, it's cheap, and it's tolerant of beginner marks (i.e., dings).

Track anvils are not bad, but they lack the mass for heavy forging.  Meanwhile, I-beam sections make an awful clanging noise that can't really be lessened.  I can confidently recommend that you just get a real anvil if at all possible.  Then you won't have to deal with those problems. 

Obviously you'll also need a good blacksmith forge too, but that's a lot easier to make than a proper anvil.




So anyway, I hammered out that round stock into a right-angle bracket.  The basic forming steps were fairly easy, at least in concept: 
1. Hammer one end flat. 
2. Make the 90-degree bend just above the flat. 
3. Hammer a V-bend in the other end, for hanging the lamp. 


The V-bend was hammered into shape using a scrap of pipe as a mandrel.  (If you wanted a sharper "V", you could use angle iron.)  Here again, the horn of a proper anvil makes this kind of work much easier.




The flat end was later drilled out to accommodate lag bolts.  I did some light de-burring, and overall it seemed pretty good.






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Mild Steel?


The lamp bracket was kind of basic-looking, but this was supposed to be functional, not pretty. 

So I mounted the bracket and put a lamp on it.  And that's when I realized something.  It bent easily.

The hanging lamp put a certain amount of torque on the end, due to the weight of it.  It was just enough that it wouldn't bend immediately.  So, everything looks fine, then a couple days later you would have this bent bracket.

Normally you would prevent this by heating that section and quenching it in oil.  Mild steel doesn't have enough carbon to "take a set" when you quench it.  (Unless, that is, you do a Super Quench... more about that soon.)

By the way, there's a reason why that bracket had to be so long.  The hanging lamp has to be away from the wall a certain distance.  I realize that puts a lot of torque on the 90-degree bend.

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Testing Unknown Iron


Before making the bracket, I should have done a "spark test" on the metal.  To do this, you get an angle grinder, clamp a piece of the mystery iron in the vise, and grind on it.  You look at the sparks.  If they have a lot of branching, it's a medium or high-carbon steel.  If they have little or no branching at all, it's either plain iron or close to it.  (Cast iron sparks do branch a lot, because cast iron has very high carbon, but that doesn't mean it's suitable for forging.)

When I was cutting this piece, I did not notice branching on the sparks.  I think it has a very low carbon content, if any.




There's another test, which is a bit more dangerous, but here's something else you could do.  (Disclaimer, again.)

You could saw off a piece of the unknown metal maybe three inches in length.  Heat it to bright orange, then quench it in ice cold salt water.  (You're not normally supposed to quench stuff that way...)  Then, clamp the piece in a heavy-duty bench vise.  See if you can break it off by hammering on it laterally.  Be careful;  glass-hard steel can shatter and throw shards.  Occasionally, it can even crack by itself due to internal stresses.

If it's medium or high-carbon steel, it will snap off easily.  A moderate hammer tap might even be enough.  If it's wrought iron it will just bend, same as it always did.  (I think mild steel could be made to snap if you really heat it a lot before you quench it, but I haven't tried this.)

You might not be able to know the exact alloy, but you will least know if it's steel or wrought iron.



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Salvaging The Bracket


There are a couple of possibilities here.  I want to keep that bracket from bending when a lamp is hung from it.

I could arc-weld a support piece at about 45 degrees.  Flat stock welded off to one side should make it possible to get at the lag bolts with a socket wrench.  I'd have to miter the ends of the flat stock at 45 degrees.  It might also help to hammer a couple flat spots in the bracket (while it's red-hot), so the steel matches up better before it's welded.  6011 is a good gap filler, but I would rather use 7018 for this.

Other alternative: Super Quench.  I've read that this method was invented at Sandia National Labs.  Basically you get 5 pounds of salt, 32 ounces of this dish soap, and 7 or 8 ounces of this stuff, and you dissolve it all in 5 gallons of water.  You would heat the metal to orange, then immediately quench it in this solution.  (Whatever you do, don't Super Quench any steel that's got more than 0.5% carbon.  I would make sure it's even below that percentage of carbon, just to be safe.)

For mild steel, I think the minimum temperature would have to be somewhere about 1550 to 1600 F.  (This infrared thermometer is supposed to read up to 2900 F.)

I've read that this method can give mild steel a Rockwell hardness in the 40's, which for mild steel is pretty incredible.  I'm sure that would add some flexion resistance to the bracket.  The lamp is not that heavy, so we don't need spring steel here. (Speaking of which: I'm sure you could make a similar bracket from a leaf-spring, but I didn't have one.  And if I did, I'd save it for other stuff such as froes, drawknives, etc.)

One more caution... junkyard steels are not always homogeneous.  Thanks to recycling, they can literally be different compositions in the same piece.  Rebar is the most well-known example.  So, I would not go directly to a Super Quench until you know how the metal responds in plain water quench, etc.

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Conclusion


This project was a crude lamp bracket made from junkyard steel.  I didn't care about making it look great;  I just wanted something that worked.  Also, one of the goals here was to make this item using scrounge-able materials, including the anvil.  If that's not one of your project goals, I highly recommend you get a real anvil.

I'm thinking I might work on this bracket some more so it looks better  Even more important, the bracket bends too easily;  that has to be fixed. 

So, for Part 2 of this project, I might work the metal to make it more decorative.  And then I might weld an angle brace, or maybe just Super Quench the 90-degree bend so it can withstand more torque.  I don't know for sure if that will work, but if it doesn't, at least we can keep track of what not to do.

Hopefully you guys found some of this info useful. 

Thanks for reading!







Gear and stuff you might be interested in... (helps support this site, too):

"Blacksmith Anvils and Stuff," $349 and up.  At any given time there could be some good ones on there;  check periodically.






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