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

[beammeupscotty]

I am of the school of thought that suggests you should size your hammer to the material and task you are working on.  I have been forging a lot of bottle openers recently  in material from 5/16 to 1/2 inch and I typically use 4 or 5 different hammers before I am done.  I have a hammer dedicated to only striking tools like spring fullers, ball end punches, center punches etc.  I NEVER strike the material I am working on with that hammer.  I am also of the school of thought that acceleration is the key and that a 2 lbs. hammer moving fast is more effective than a 4 lbs. hammer moving slower.  The idea of just letting a heavy hammer drop, as has been suggested in this thread, is to me, absurd.  When I see someone doing that and not raising their hammer high and really accelerating it, with a wrist snap at the end, I always get the impression I am watching someone inexperienced.  That  is what I typically see beginners doing... all forearm and elbow and no wrist.  

[Everything Mac]

I did some research into this whist looking for information on hammer related injuries. And I came to the same conclusion that you guys have. 

 

If however you could swing a 4Lb hammer at the same speed as your 2lb'er then yes it would of course be more efficient. 

 

 

What hasn't been mentioned is where you grip the hammer though. I've noticed in various videos that people using much heavier hammers tend to hold it right up near the head, this would have earned me a clip round the ear in my early training days. 

 

I'm sure I have read (I am paraphrasing here) - that holding a hammer near the head would increase your level of control over the hammer but reduces the "lever" of the swing and thus you loose out on a certain amount of power in the swing. 

- conversely holding the hammer right at the very end of the handle allows for the maximum velocity to be obtained but you do so at the loss of control over the hammer, and it is more likely to be inaccurate. 

 

- Therefore holding the hammer in roughly the centre of the handle allows for a compromise of control versus power - i.e. it is the most efficient. 

 

I've also tried to look at hammers from around the world and throughout history and it seems that a 2Lb weight is pretty common. I suspect this is for a reason. ;) 

 

Having said that, it's all so very subjective that it's almost a moot point. I know slight framed ladies who struggle with anything over 2Lb, but I also know of guys who will happily use a cut down 7Lb sledge :O 

 

My advice would be to use what ever the situation calls for and what ever feels comfortable. Personally my hammers weigh in a range from 1Lb to 4LB - above that they're sledge hammers. 

 

All the best 

Andy

[Charles R. Stevens]

Actually, like the sledge if you choke up a bit, and turn the hammer so the head is standing up its easer to lift as you don't have the hammer leverage, then as you get her strait up over head start your swing letting the hammer handle slip forward mid swing. If you want to really get in to your swing with a big hammer! It's just so versital to use a big hammer, choked up or full handle I admit it takes getting used to and you use a differant technic. I just prefer to take heavy rhymec strokes than to peck at the steel like a chiwawa in heat! .

[Jack Evers]

Notthing to do with hammer weight, but some might be wondering about the odd (and not symetrical) shape to those shoes. In an Eagle eye contest, the contestant gets a look -typically 10 seconds - at a foot and makes the shoe to fit that particular foot. The foot wasn't symetrical. Looks like a left hind to me.

[Everything Mac]

Actually, like the sledge if you choke up a bit, and turn the hammer so the head is standing up its easer to lift as you don't have the hammer leverage, then as you get her strait up over head start your swing letting the hammer handle slip forward mid swing. If you want to really get in to your swing with a big hammer! It's just so versital to use a big hammer, choked up or full handle I admit it takes getting used to and you use a differant technic. I just prefer to take heavy rhymec strokes than to peck at the steel like a chiwawa in heat! .

 

The day I struggle to lift a hammer is the day I stop smithing. 

[Charles R. Stevens]

Mac, I thaught that was why the invented power hammers ;-)

[Charles R. Stevens]

Watch the visitors again, especially Brian's, you'll we that he will deliver a few very heavy full handle, full sroke blowes then chokes up and planish. It's not all about the sheer mass it's the fact that when you need 4# and 16" of handle you have it in hand, wile you can choke up for a more delicate blow. No need to reach for a diferant hammer mid heat

[rockstar.esq]

Alexander Weygers book on blacksmithing mentioned that heavier hammers upset stock deeper into the material than a lighter hammer.

 

I suspect he's touching on a point that hasn't come up which is that the hammers mass relative to the mass of the stock has a great deal to do with the energy transfer.

 

I've certainly found that high velocity blows from a lighter hammer tend to excel at tasks like riveting because the force seems to penetrate the stock less.

 

The framing hammer analogy presented earlier didn't mention the mass of the work being done.  The nail is small and offers little resistance to driving.  Overcoming the static friction of the started nail allows the hammer to drive the remainder of the nail with less force.  Therefore velocity is a big asset as it allows a lighter hammer.  Aside from punching or chiseling, the blacksmith's hammer isn't encountering a similar load.  

 

Charles Stevens made a solid point about how moving a wall with a sledge isn't too tough and it doesn't damage the material.  The sledge's mass is closer to the mass of the wall than the framing hammer.  Thus it overcomes the static friction more readily allowing the wall to slide further.

 

Consider the power hammer versus the bodyshop planishing air hammer.  It makes sense to me that if you're working material with low mass (sheet stock) the planishing air hammer is a perfect approach.  If you're working bigger mass - the larger mass of the power hammer is the way to go.

[SpankySmith]

I've had surgery (years ago) on both my wrists and have since had to adapt the way I swing a hammer - it needs to stay in plane with my forearm as much as possible and not involve a "wrist snap" as mentioned above.  To do that it's sometimes necessary that I choke up on a hammer.  I've had people tell me that decreases the power transferred to the material, but they usually say that while I'm on my 4th or 5th nail (driving into wood) and they're still trying to get their 2nd one in.  My point being that we are very adaptable creatures and just because it doesn't "look" like it should work, it often does.  At least in my case.  

[78sharpshooter]

I was thinking of using 1/4" or so copper cylinders, 2 and 4 lbs steel cylinders dropped through a vented PVC pipe from exactly the same starting point to impact the copper cylinder and then measure the copper cylinder to see how much it was squished. While it is obvious that there is a direct relationship between energy and plastic deformation, that relationship may not be linear and instead might be a curve or logarithmic function in which 2 blows from a lighter hammer may not equal one blow from a 2x as heavy hammer at equal velocities. It might also be interesting to see if there is a difference in thickness of copper cylinders when doing this on a 120 lbs anvil and a 320 lbs anvil.

[Charles R. Stevens]

Remember to anneal tha copper between blows

[Chinobi]

lot of variables some into play when you start to bring it into the real world.  for instance, after the first blow from the smaller hammer the surface area that will be in contact at impact is now going to be larger, which will reduce the 'felt' PSI of the impact as it is spread over a larger area.  should be a good way to keep velocity constant, may need to include some kind of catch to prevent bouncing secondary impacts.

 

copper also work hardens, so if you are trying to determine a precise curve that may influence trials that involve multiple impacts as well

 

that sounds like a fun set of experiments though, shame I wont be in SD for much longer than the conference this weekend or I would try to stop by and lend a hand =/

 

edit: actually, if you want to get rid of the idiosyncrasies of deforming metal and just determine the amount of force supplied by the blow you could switch the copper cylinder for a rod restrained in a friction collar and measure how far the hammer blows drive the rod through.  that way the resistance is constant and you can measure linearly how far the rod traveled and graph that.  but of course that is an attempt to bring practice as close to theory as possible, so the results should end up pretty close to the math.

[rockstar.esq]

78Sharpshooter-  The math behind the physics is fairly straight forward for the layout you presented.  The velocity of a falling object is going to be a function of it's time of fall and it's air resistance.  Given that you're going to use steel cylinders with the same profile facing the air- you can effectively cancel air resistance from your consideration. Gravitational acceleration is approximately 32.17'/sec/sec.  That means it'll fall about 32' in one second and about 64' in two.

 

Obviously you get longer time of fall with greater height

 

Velocity at point of impact will be equal to the square root of (2x32.17*Height)

 

I ran through it quickly and a 1' fall will get you approximately 8'/sec of velocity.

 

Doubling that velocity would require approximately 4' of fall.

 

Please note that the mass (weight) of the hammer has no bearing on it's velocity in a fall that omits air resistance.

 

Energy calculations favor velocity exponentially.  That means that you can double kinetic energy by doubling the mass or you can double kinetic energy by increasing velocity by roughly 41%

 

Doubling the velocity increases the energy by 400%

 

So getting back to your experiment - the 2lb hammer would need to fall 1.97' to equal the kinetic energy of a 4lb hammer falling 1'

 

On paper it sounds like speed is always the best solution to get kinetic energy.  

 

In reality, it's about getting work done. The most efficient applications will match the tool to the stock.