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Hi all,

Lately we've been making an awful lot of hammers; mostly from 1045. Forge, grind, polish, then heat treat. Heat treat consists of heating each face to non-magnetic or just above, and quenching in water-aggressively moving it to break through the steam jacket. Then re polish and temper using hot drifts-watch the colors run and quench again.

My question is this-is tempering nessesary? I have read about Tom Clarke, IIRC he used 4140, heat treated (quenched in...oil? I'm assuming) and then did not temper. Maybe I read false information about that, but I've heard others mentions not tempering as well. Is this specifically talking about 4140? Or in general for hammers? What is it really accomplishing? I understand it will make the hammer less brittle-so it would divot or dent before it would chip...

What are your thoughts on it? We always temper because that's how I learned, but curiosity is getting the better of me.

Aaron

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A review of wot tempering does is in order rather than just doing it cuz we do it. And a vital is to see wot the manufacturer say about the full heat treart of the steel..then based on wot you find tailor to your intended use.

If I use ahammer for only striking hot steel. I will stick with  harder faces than if I use it for striking top tools that may be harder and i want to use a softer face for..I know that face may need dressing but it is worth the trouble.

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Speaking strictly from my own personal experience: I have oil quenched my hammers and then slow baked them atop my forge to temper.  This method has served me well and I will likely continue to do it this way.  I have a huge handled hot-cut with about a 2 inch blade that I acquired cheaply because it was chipped at the striking end.  I redressed it, grinding away the chips, only to have it chip again at first use.  At that point I removed the new handle and tempered the striking end and once again redressed the tool... it now works very well!  The hot cut is likely very old steel and I have discovered that such steel is more prone to over hardening problems than modern steels... it seems to get brittle more easily than most modern steels and especially than 4140 which is designed for toughness and even poorly heat treated performs better than you might expect.  In working with my hammers I have found them to be just right for me... pretty hard and taking a lot of use before needing a bit of redressing, yet soft enough to use for striking my soft striking ended tools without problems.  Since a hammer meant for forging is such a heavily used tool and will be used in such a variety of processes I feel it well worth my while to do the best that I can with it's heat treatment!  I have no doubt that I might cut some corners and still have a serviceable tool.  I am not the sort to move in that direction however, I am the kind of guy who takes an hour to tye a fly rather than the six seconds that one famous pro is noted for... but my flies have been known to catch over 300 fish and then retire in serviceable condition yet!  I did a lot of work for a guy who had a famous quote above his office door: "There is hardly anything in the world that someone cannot make a little worse and sell a little cheaper, and the people who consider price alone are that person's lawful prey."  (this quote is widely attributed to John Ruskin but there is some doubt of his authorship).  Personally my approach would be to get more efficient at tempering rather than to skip the process... a good oven would treat many hammer heads at once with repeatable results. 

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I have heard people talking about hardening and not tempering. I have a hammer that I use as an example, for when I am teaching heat treating in my classes. I was given this rounding hammer from a farrier friend who was taking a farrier course. They were heat treating rounding hammers and they all were hardened and tempered, except one. One was hardened and not tempered because Ken was going to temper it later, He put it in a drawer at home and forgot about it. He was rummaging through his workshop about a year later and found the hammer that hadn't been tempered. The whole hammer head was tiny cracks, similar like crystal structure. This hammer had NEVER been been used to strike ANYTHING since it was hardened. It had too much internal stress and it relieved the stress by itself.

 

Hardening makes steel strong, Tempering makes steel tough. If you make anything too hard, you are taking the risk of creating projectiles that you have no control of where and when they are going to release and what direction they are going to go. I know there are blacksmiths who have steel fragments in their legs from such projectiles, What about the kids that might have been watching?????? It is better to err on the side of caution, Temper hammers slight softer that you might think you want. It is easier to dress a hammer than build someone another EYE!!!!

 

Neil

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My forging hammers have all been made of old 18 wheeler truck axles. I think they are 1045, they average about 2" in diameter, and I square them up on the trip hammer. I harden the face only in water by heating at the edge of a coal fire. I don't want to harden the eye, as the difference in the rate of heat abstraction may cause the cheek(s) of the eye to crack. I quench the head in water vertically with agitation.I  bring it out when it's still a little warm removing it when the 'cush' sound stops. I have a tempering tool I made of 7/8" square mild steel. On a handling length, I turned an unwelded eye on the end to where the inside diameter is a snug fit around the hammer head. With the hammer head placed quickly in the vice, hardened head up and sanded to bare metal, I place the welding-heat eye over the hardened head and watch for tember color. I've had success taking the face to a dark straw.

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I forge hammer heads from 4140 (axes too) and I quench it in the slower of the two quench oils from McMaster Carr.  I then draw temper at around 535 degrees.  This makes for a tough head.  I would *not* want to use an un-tempered hammer head.  No point to it.  What's saving a bit of time compared to not having your tool catastrophically fail on you?

 

Frank - I enjoyed very much watching you make hammer heads years ago at IronFest in Grapevine, Texas.  :)

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 I love it four different methods,! Thought I'd do a little research before I HT my new hammer tomorrow, and glad I did. I am using old carriage axle steel on my hammers and no way to get spec sheet, so , I wing it carefully. This is only my third made hammer and the last one I got lucky on for it's still not deformed and only needs a dress occasionally. Wish I could mix all four methods.

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For unknown steels the correct method of heat treating is to leave a piece to run experiments on to see what works best.  I generally start with the slower quenchants and proceed toward the faster ones.  Once I get good hardness I then start trying tempering temperatures again starting with the lower ones and proceeding towards the higher ones till I get one I like.  If I have a lot of that particular steel I'll document this on a 3x5 card so next time I can just work on adjustments for differing end uses.  As for steel for axles: PTREE used to work in a factory that forged them and posted over at anvilfire the two alloys generally used in the USA based on diameter of the axle:  recently made axles are generally 1050H for smaller ones and 1541H for larger ones. (with 1 3/8" unforged diameter being the line of demarcation and 1 3/8 being on the 1050H side)

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Hi Aaron, I thought I'd chime in on the information about Tom's hammers. I lived about two hours from him, so I made a lot of visits to his shop. Even had the fortunate chance to work for him for a few months before he passed. Tom made all of the forged hammers from 1045. Its dead simple, and forgiving, to work with in the shop, as I'm sure you've discovered. they were quenched in collected rain water, due to the purity. His shop was in a area with HARD water. 

He most certainly did temper his hammers. There was an old kitchen oven in the shop that he baked them in, somewhere around 475 degrees F. Its hard to beat an old oven for that nice, slow, tempering bake, plus the large volume for multiple hammers all at once. And they come out with such nice colors, too! I've seen how much you like those temper colors! His end goal was between Rockwell 50C - 54C. 

IIRC, I think he mentioned that he used the 4140 for the cast hammers he did. Seems that what he said in one of our conversations. Though I cannot recall what the heat treat process was on those.

And just to add my two cents, everyone else is steering you right. Tempering is a must when making any struck tools. One day it clicked that heat treating is really a balancing act between hardness (brittleness) and toughness. I think it happened as I was looking at a graph on a heat treat spec sheet. It was laid out clearly, and just made it simple to understand. Anyway, when you quench from critical, the carbon and iron atoms are having their crystal structure rearranged, from austenite (crystalline form when steel is at critical) to martensite (the final, hard crystalline form). The thing about the martensite transformation is that there is some volumetric change due to different densities between martensite and austenite. That change, coupled with the naturally high strain the martensite crystal forms are under, creates  a lot, and I mean a lot,  of stress in the hardened steel. That strain stress is a part of the hardness of a hammer, but like all of us, needs to relax some or it will crack. So tempering helps to relax the crystalline martensite (obviously, the higher the tempering temperature, a higher amount of martensite is relaxed). And that is where the balancing act comes into play: bake at just the right temperature to be hard, but also tough. So there is, I'd say, a good reason we are taught to temper :)

I picked up a lot of this trying to make hammers from 1080. lets just say it was quench crack city for a looong while. :( :blink: :angry:

Hope this short book helps!

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This is great material to read, especially as a new guy (which I am). 

I would guess that if internal stress is that big a deal, the piece should be normalized before heat treating to reduce those stresses.  Then you would have a safer quench, but still need to temper. 

I have been trying to decide whether top tools made of 4140 need to be hardened, given that they are in contact with hot metal so much (even if cooled as you work).  For example, I made a handled hammer eye punch and a hot chisel, and am planning some hammers, but I was not sure whether to bother hardening them at all.  For one chisel, I hardened, but will have to temper before using (I forgot, but in future, I won't stop a project until tempering is done, just in case-- even if it's just fire tempering).  I made a little hot cut hardie out of W2 welded to a scrap hardie plug and quenched in water, but it chipped to bits even against hot metal.

I was wondering if I should harden the hammer heads for the same reason, but I think I will, and then temper to dark straw.  I like the hot drift approach.  Right now I can't keep water in my shop because it freezes so xxxx fast (-20*C).

 

Please read up, Annealing is a form of heat treating

 

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Dark straw is a bit over hard for tempering hammers and struck tools, IMO.  I temper my forging hammers to a deep blue and find that just right in most cases.

 

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Of course the drawing/tempering temp depends on the alloy and intended use, (and preferences of the user).  I can't make suggestions about 4140 as I tend to use alloys with a higher hot hardness like H13 for tools that get buried in hot steel, (or iron).

In general you are aiming for added toughness rather than brittleness.  For Q&D tools I use 5160 and normalize for drifts.

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4 hours ago, ThomasPowers said:

For Q&D tools I use 5160 and normalize for drifts.

TP, could you expand on that a bit? Say you were making tools from torsion bar (assuming that's 5160); I see that you'd normalize it if you made it into a drift, but if you were making a smallish hammer, you'd harden and temper it to...?

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What do you want to do with it and how do you like a hammer to do that?   Do you want your hammer face harder or softer than your anvil's face for instance?

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Good questions. I was just thinking in generalities, but that may be too general a question.

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Yeah, my anvil is quite soft (I'm not sure of the specifics but it's so ductile I can 'form' the roundness of the edge with a hammer with relatively mild blows).

My question was whether non-hardened 4140 would be hard enough to use as tools like hammer eye punches, hot chisels, and maybe hammers.  I thought the hardness would be pulled out as they heated from the work, but I think I need all the efficiency I can get from my tools if my anvil is that soft.  But I risk denting the anvil (no big deal if it's that ductile - I can just pound/grind it back into shape, as it won't chip).

I get that hardness is both a preference thing and a safety thing; being a new guy, I was wondering if non-hardened 4140 was just not hard enough.  I'll just have to use these tools some more to see! 

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I have a dead soft hammer I tend to give new students who "hammer like lightning---never hitting the same place twice!"

It works on hot metal---and so a good teacher to keep their metal glowing when hammering as well.

In general I  prefer a hard face hammer.

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