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Trying to make a center punch - and learning about hardened steel

 
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So tonight I attempted the make a center punch BB (https://permies.com/wiki/134238/pep-metalworking/PEP-BB-metalworking-sand-centerpunch). I was almost successful. I found an old rusty chisel, cut the ends off, threw one end in my drill and ground the other end down with my bench grinder, then used it to hammer some metal! Wow look at me go, I thought. Then I looked at the point on the punch...it wasn't as pointy no more. Disappointed, I sharpened it again and hammered some more dents just to be sure it was dulling. It was, sadly.

So what is the issue here? One thing to remember when cutting or sharpening hardened steel is that you do not want it getting too hot. Otherwise you could end up losing the hardness. I took care of this by dipping the punch in a cup of water after about 10 seconds or so of grinding. I was not as careful when cutting the ends off so that may have been an issue too...but I doubt it.

Okay so if I was careful with the temperature and I was working with hardened steel, how did it end up soft? The issue is that I may not have been working with hardened steel, at least not where I was grinding.

Tempering is an extra step added onto an already pretty energy intensive process, so manufacturers will often only harden the part of the tool that really needs it. So for example my chisel would likely not be hardened all the way through, it will only have a hardened blade. See my mistake now? By using the shaft of the chisel, I was using regular old steel. The good news is that it is high carbon steel which means it has the potential to be hardened. Unfortunately I do not have any way of achieving tempering temperatures so I will have to search around for already hardened steel to use. Off to the scrapyard I go.

For those of you interested in learning more about tempering, check this video out. You get to watch a knife be created and you learn way more than you think you will.

IMG_20210127_185913_591.jpg
Old chisel - I think
Old chisel - I think
IMG_20210127_191411_122.jpg
Ends cut off
Ends cut off
IMG_20210127_192453_102.jpg
After being 'lathed' for a bit
After being 'lathed' for a bit
IMG_20210127_193316_583.jpg
Ready to dent metal!
Ready to dent metal!
IMG_20210127_195718_742.jpg
So it dents - great but did it keep its point?
So it dents - great but did it keep its point?
IMG_20210127_193629_388.jpg
Not really...see above for why
Not really...see above for why
 
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Offhand, looks like a decent tool. How hard was the steel you were hammering into?

The chisel would have the same chemical composition all the way through. I wonder if you're confusing hardening with tempering? Hardening means heating and then quickly cooling (quenching). Tempering is reducing the hardness by baking in a controlled manner, so that a balance of hardness and toughness is achieved. (That's my version anyway; there are smiths here who can explain it better.)
 
Cam Haslehurst
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Douglas Alpenstock wrote:Offhand, looks like a decent tool. How hard was the steel you were hammering into?

The chisel would have the same chemical composition all the way through. I wonder if you're confusing hardening with tempering? Hardening means heating and then quickly cooling (quenching). Tempering is reducing the hardness by baking in a controlled manner, so that a balance of hardness and toughness is achieved. (That's my version anyway; there are smiths here who can explain it better.)



I must be confusing them as this is all pretty new to me. I know the chisel is the same composition throughout, but my thinking is that only the blade was originally hardened through quenching process while the rest of the chisel has the potential to be hardened but it hasn't been yet. Is that clearer? It might still be completely wrong but that was what I meant to say the first time around.

If only the blade was hardened, then by cutting it off I was left with high carbon steel that had not been hardened by the quenching process. Do you think this could be the case?

As for the steel I was hitting, it was definitely mild steel. It's what I used to make my bike fender and christmas ornaments this year, and it wasn't very hard to dent.



 
Douglas Alpenstock
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Okay, I see what you're getting at.

If you have access to a propane torch, you could probably heat and quench the tip to harden it for durability.
 
Cam Haslehurst
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Douglas Alpenstock wrote:Okay, I see what you're getting at.

If you have access to a propane torch, you could probably heat and quench the tip to harden it for durability.



Ouu I didn't think I'd be able to do that with propane heat, I thought I'd need an oxy-acetylene flame or something like that.  I think I will have a go at that for sure. More updates to come!
 
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Yes, don't give up! With the projects you've been doing, heat treating will be a good skill to have. A good plumbing torch may get the tip hot enough, but many torches I've seen lately seem to be quite anemic. Another option is to place two torches facing each other to heat both sides of the punch point at once. I'll just about guarantee this can get it hot enough. A third option would be to make a mini-forge with your torch as the burner. Clay/perlite mix with about a one inch hole through the middle, and a hole through the side just big enough for the torch nozzle will heat a much larger piece by keeping the heat contained. The torch can be used to temper it after, or a cooking oven is a more reliable bet.

I once made a small electric forge from one of those old heaters that has the two vertical ceramic tubes with nichrome wires wound around them. I took one tube and shortened the wire until 110v made it glow orange. I surrounded the tube with ceramic wool insulation and it worked well. It takes several minutes to get hot, though.
 
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When you harden it you want to harden the working end not the entire chisel/center punch. https://www.youtube.com/watch?v=__3vmtFFy3s&feature=emb_logo
 
Douglas Alpenstock
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Hey Robert, that's a good link. For the tempering portion, some folks like to use a toaster oven (or the main oven in the house, until they are given strict orders to cut it out).
 
Robert Ray
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Some knife maker friends have tempering ovens. Working with a tool that is struck I want it hard on the business end but not so hard as to make the struck end brittle. Drawing the working end to that straw color after a few tries becomes very easy. I make my own chasing tools from water hardened tool steel. They can be quite expensive if you buy them. Custom sizes and for a particular project is something that you just have to make yourself.
There is nothing that says so much as my wife's raised eyebrow, sounds like you have had similar discussions?
 
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The reason the tool wasn't hardened all the way through is for toughness, if it was all hard enough to punch steel, likely it would not be as tough. Its a balancing act, when I forge an axe I only quench the inch or so on the edge; that way the axe will hold a fine edge and the back is soft (or tough) enough to take the shock of being repeatedly struck into a piece of hard wood.

Similarly I only harden the blade on a knife, not the tang (handle portion). It helps to give the knife some flexibility and toughness., while the edge retention is good.

Recently I have been forging my own engraving tools, to engrave steel with. I am using old files as the stock, and only quenching the first half to three quarters inch on the tip. Then I temper it back somewhat, that way I can beat on the back of the graving tool and it will take the hit, but the edge will cut steel.

It takes some experimentation, don't give up.

If you can heat the tip to cherry red and quench it (the tip) in oil, it will harden. If you only do the tip and then let the residual heat left in the tool temper it slightly it'll most likely be hard enough.

 
Cam Haslehurst
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Hey folks thanks for all the great advice. I'll have a go at hardening it. I only have one torch, and no access to clay or perlite right now, however I do have an old makeshift rocket stove I threw together from some coffee cans and soup cans when I was learning about them. I think I can make it into a makeshift propane forge with just a bit of work.

I just watched that video and man this stuff is really an art. All the details involved in just the basic process make me respect the blacksmiths out there a whole lot more now.

*Edit Ben I just saw your reply. Thanks for the input and it is now stuck in my head that I only want the tip hardened. I also need to not think of hard and tough as synonymous. They might be in some every day terms but not when it comes to metal properties.

I will update when I try this out!
 
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Cam Haslehurst wrote:So tonight I attempted the make a center punch

In shop when I was in school all of the projects was to make a cold chissle out of a piece of rolled steel, shape and harden the cutting surface, the grade was pass or fail, when you finished our teacher would take a nail and lay it on the anvil and then use your new chisle to cut it in half, if it cut the nail without damaging the chisle edge you passed, if it made any indention in the edge you failed and started over.  one fella had hardened to far up the shaft of the chisle and when the nail was cut it also broke the chistle.  The reason your punch is not hardened all the way to the end is it would be like that one fellas and brake, the softer steel alows it to absorbe energy both when being hit and the equal reaction from the object being cut.
we hardened the edge by cooling it in used motor oul after heating it.

 
It's a tiny ad only because the water is so cold.
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