78sharpshooter

Which is faster to move metal; 4 lbs hammer or 2 lbs hammer with 2x the blows

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(POWER: This is how much energy your hammer can deliver to the piece. This applies whether it is a Nazel 3b, 100#Little Giant, or a 2# crosspein. Mass x Velocity squared so a big slow hammer might do less work than a slightly smaller, but faster hammer. A note about sledge hammer work, if you feel slow swinging the heavy hammer, you might be more efficient switching to a lighter hammer you can swing faster. I have seen a lot of people think 'I need to use the bigger hammer', when they would have been better off swinging a lighter hammer faster, and more accurately. Heavier hammer blows do penetrate thicker stock better so you are not just affecting the surface.)

sjs post from April 9 2014 on page 6 about half way down the page.

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Energy = Mass x Velocity squared...  the number of blows have little to do with it... Your question is higly dependent upon the velocity at which the hammer is being swung, if we assume the velocity is the same then we have an we get 4v² and 2(2v²) which if my memory of order of operations still serve, are the same... That is,1 blow with a 4 lb. hammer delivers the same amount of force (cumulatively) as 2 with a 2lb... I could be wrong, as math has never been my strong suit... Any mathemeticians want to chime in on this?

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If velocity is constant then doubling mass will double energy, problem is most people can swing 2 pounds a lot faster (velocity, not swings per min) than a 4 lb, so getting a straight comparison is tough to do by hand

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What is the average weight of the hammers in that video? Two pounds, three pounds? 

 

I was cold straightening  a well-bent 1/2" diameter 'U' bolt off of a leaf spring shackle the other day.  First I put it under my 3 ton rack and pinion press.  Put all of my 220# on the 'legal' lever.  Did not even flex. Took it over to my Hubs of Hades anvil and gave it a short, sharp rap with the broad face of my short handled (9-1/2") 3# Cross Peen hammer.  The metal moved with ease. Finished it out.

 

I don't know how much force that hammer blow delivered, but didn't it have to exceed three tons?

 

My command of mathematics is poor, otherwise, I would not now have more questions than answers.

 

I believe though, after watching the preceding video, and from my own experience, Acceleration is King.  I have hand split dozens of cords of oak, et cetera, in my lifetime, and it's just something you know (well I think I know).

 

One of the other things I have been noticing in these competitions is the shape of the hammer face.

 

Please excuse my machine shop usage of the term Upset. In metal removal, That first 'moment' when the cutting tool enters the work, is when the upset begins. Similar to another phenomenon called stiction. It can be directly observed on machining center power meters, that more power is consumed as the cutting tool crosses the moment of inertia, and the upset or plastic deformation is initiated.  Programmers (hopefully) sometimes compensate for this with code. 

 

Think about what happens when we dawdle in a hacksaw cut.

 

There is a bit of code in the competition hammer face.  Since it takes more energy to initiate an upset, and less energy to sustain it, is there not a slightly spherical radius on your favorite hammer?   Thus, first contact is Maximum Acceleration at Minimum Surface area. Once the material has begun to move, the net energy required to continue plastic deformation is reduced.

 

I may have just painted a bulls-eye on myself, as I know there are more than a few talented and accomplished Machinists on this Forum.  Fair Game.  I have no degrees in engineering, let alone finger-painting.

 

So I agree with SJS's Post #108

so much as I am able to understand it.

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You must take into consideration the fact that well placed blows on a well placed piece of stock at the right starting heat will make LARGE difference.  Drawing points on 3/8 square compared to 1/2 square ( square points same length ) off the far side and using 6 blows on each size of stock can be accomplished fairly easily.  This with a 2 1/2 - 3 lb hammer (my choice anyway).  The trick is to have the right combination of top/bottom tool to forge the points in the most efficient way ( and maybe a few dress blows afterward too ).  You will yes use larger strokes and harder blows on the larger stock but the same can be accomplished.  The physics involved has been discussed.  None of this makes a large difference if you don't have absolute control of the blows made ( and I mean hand swung blows ).  If I were to have another hammer of the same handle stock and type with a larger head I MIGHT be able to move more but don't know.  I can point 48 of what I listed ( running a gasser ) in not that long of time.  I might add that the smith running the hammer and the specific needs will dictate the size of the hammer as well.  I tend to go a bit on the heavier side but I'm not a farrier.

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Yep hammer control is 99.9% of the equation... in general though a larger hammer allows you to move metal at a slower more sedate pace in my experience... I seem to move about the same whether I am swinging a little hammer like a rabid chihahua on speed, or just thumping away with a 5# whacking stick. Use what is comfortable for you and gives you the best results.

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Arithmetic aside momentarily, there is sometimes the human factor in learning the hammer swing. I see beginners getting into the habit of hitting almost everything with rapid, dinky blows and using mostly the wrist and forearm. When I tell one of them to hit it harder, he/she doesn't; they speed up the rhythm (cadence), yet with the same "dinkyness."  I yell, "I said harder, not a speedier rhythm!!" To hit harder, the hammer is lifted higher and the cadence may be slowed, but each blow will be more telling. This brings us to accuracy. Neophytes seem to avoid lifting the hammer overhead, because they think they lose accuracy. I yell, "Get over it!!"

 

Reference the farriers in a forging contest, most riding horse shoes are 5/16" x 3/4" and the rounding hammer is about 2.5 pounds. The contestants are working at a higher rate of speed overall, than they would normally. I've done it, and it is exhausting.

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The depth of the movement of the metal with a heaver hammer has a telling effect, inertia seems to ad just a bit to the mix. In truth I'd rather choke up on a 4# hammer and take less BPM, than be out on the end of a 2# hamme and hitting at twice the BPM.

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Frank; wow, I run into that all the time too---makes me want to get a wrist brace and put it on them so they can't bend it!  You tell them that the hammer should be up by their ear and they still want to plink plink plink instead of *whomp* *whomp*.  Sometimes a heavier hammer that they can't use only with the wrist can help---but it's hard as I often tell folks not to use too heavy a hammer to start with to help avoid RSI. 

 

Starting out new folks I often will "suggest" they change hammers as I watch how they are hitting.  Those who strike like lightening get the dead soft hammer! (strike hard but never hit the same place twice...)

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I had a hammer conversation with Glen just the other day. My hammer experience came initialy from carpentry. I learned early on to "swing with a purpose" , especially when framing. I don't tap nails in, I drive them, with as few blows as possible. This requires some momentum and accuracy. While not apples to apples, when I picked up my 1st cross peen, I think that mind set did help. I started with a 2 lb cross peen, but have discovered I am preferring a little heavier, and am using a 2 1/2 - 3 lb hammer now for most work and a 4lb for larger material. I'm in the same camp as Charles, I prefer less BPM with a heavier hammer.

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lots of variables here...   I started this hobby with tennis elbow in my hammer hand.  Some folks get it from this hobby.  Mine went away and has stayed away.

 

I tell folks to Drop the hammer not swing it.   To me a heavier hammer with well placed methodical blows does the trick.   Let the weight do the work.  You just have to lift it higher and guide it as it falls and add some energy.   But the higher you lift the less continuous energy you add over the length of the fall can make a huge impact.

 

So what is heavier?   I have a 2lb hammer.   This will wear me out if I am working something significant and not just tweaking a shape.  If tweaking a shape you can possible tap it or bend with your tongs.

 

I like my 3.5# hammer overall.   I tell folks to aim and mostly drop it acurately.  Take your time to aim.  Lift it above your head.   Add energy to the drop as needed but this is not meant to be excessive.   Let it rebound to help with the upswing.  This means you have to almost release it free at impact (loose grip) then grab it back on the upswing. For me the upswing is should be most of the energy except when I am doing some serious drawing out.  Like say 5/8" tong handles.     Depending on your work this could be very different.   I could also see from the video that small accurate taps could help one creep up on the needed design.  

 

Let the tool do the work not the body.

 

But I have a hobby..   not a person in competition....  ok my 2 cents

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I think Frank nailed it. This is a forging competition, not a good illustration of how to swing a hammer day-to-day.

 

I would also add that while they are interesting and informative, I don't think mathematical equations are going to be of much help. 

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Just use each hammer for a month each doing the same work and see what works best for you. One good friend uses a five to six pound rounding hammer with a short handle, for everything. Took him a little getting use to but works for him. He uses it all day long. He is also twice my size. I use a two and a half to three pound and can keep up with him just fine. I stopped using my six pounder when I stopped driving bullpins to line up holes.

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Sounds to me like we need to have a forging competition. I will be glad to participate in this. I will use my 4lb. 10 oz. hammer and someone else can use as light a hammer as they like. We can start with any size stock you choose. But, all joking aside, I agree with all that said hammer face and accuracy are the key. Most of the time I do not use my hammer when other people are using lighter hammers to make sure they do not think they have to use a heavier hammer to get the work done on small stuff like 3/8" square. a 3 lb. rounding hammer works fine for the lighter work. Just had to throw out my opinion. I learned a lot about heavier hammers from working with Brian, I used a small hammer for 5 or 6 years when I first got into this, then around 2004 I started using a 3 pound hammer. around 2010 I switched to a 3.5 lb. hammer, I ended up selling that hammer in Canada in 2012, and have been using a 4lb. 10 oz. hammer ever since.

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From the framers point of veiw, if a wall is out of plum, or you need to persuade a 2x in to place, a framing hammer will mash, dent and mangle the wood, wile a "gentlal" tap with a slege won't hardly mare the serfaces but the wall will move ;-)

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As stated_physics and equations won't solve this, but the concentration has been on energy. Momentum  (mass times velocity) is also conserved. Energy comes in several forms with deformational energy being a major one. For example, safety in cars,. In my youth, many decades ago, cars were built like tanks and in a collision the deformation was apt to be in deforming the occupants. Todays cars (race cars being an extreme example) are pretty flimsey, but in a collision the energy goes to deforming the car (parts fly everywhere) not the occupants and folks survive some pretty spectacular crashes. - The car damage can be fixed by throwing money at it - better than people damage. Most of you already know this, but if you want a shallow upset use a light high speed hammer, for a deep upset use a slow heavy hammer, or as Charles says trying to move a wall with a light fast hammer rrsults in deformation of the framing lumber. A sledge moves the wall.

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Mark Aspery maintains that a 2 lb hammer, swung twice as fast, delivers 4 times the force of a 4 pounder.

Dave

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Mark Aspery maintains that a 2 lb hammer, swung twice as fast, delivers 4 times the force of a 4 pounder.

Dave

 

So why not swing the four pound hammer twice as fast?

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Posted · Hidden by Steve Sells, April 20, 2014 - No reason given
Hidden by Steve Sells, April 20, 2014 - No reason given

hit it like someone owes you money.

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The one advantage a lighter hammer has over the heavier hammer is it tends to have a smaller contact area. One of my fave rite hammers is an old cross pein with a round eye. Funky to handle, I usually use a peice of hoe or sovel handle, then rasp it to shape so it hangers right. But it's shaped almost ball like, being thick and round in the middle, having a face only about 2/3 the diameter of the middle around the eye , and a smallish pein it's only about 2# and lives on the shoing rig for when I do general forging (hoof picks and such)

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The argument is about which variable will increase the effect (energy) more when the other is held constant. It's a moot point that you will get more benefit if you increase BOTH variables at the same time! Plus, If you are physically capable of jumping from a 2 pound hammer swung at (for simplicity) 'regular' speed to a 4 lb at double, it's a fair bet that you were working far below your potential to start with.

Aspery's point in bringing this particular equation into the mix (obviously I can't speak for him, but I have read all 3 of his books and taken his 5 day course, make of this students opinion what you will) is to illustrate that you don't NEED to reach for a big honkin hand sledge to get more 'bang' for your swing, rather that you can increase your power just by improving your swing technique (let's face it, it's geared towards new folks like me who are still beginners or are entirely new to all of this, or people who are looking to improve efficiency) with the intent to increase head velocity at the time of impact. Usually by maximizing the range motion of each of the pivot points in your arm and snapping through with your fingers just before impact, which will REALLY goose up velocity, and therefore energy, without needing to exhaust yourself lifting and swinging a heavier hammer.

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...is to illustrate that you don't NEED to reach for a big honkin hand sledge to get more 'bang' for your swing, rather that you can increase your power just by improving your swing technique...   ...with the intent to increase head velocity at the time of impact. Usually by maximizing the range motion of each of the pivot points in your arm and snapping through with your fingers just before impact, which will REALLY goose up velocity, and therefore energy, without needing to exhaust yourself lifting and swinging a heavier hammer.

 

 

I think this is the point, and it transcends the particulars of weight or the size of the individual.

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