Anvil size vs hammer size, 2% or 10:1 or 15:1

[Arbalist]

I have no idea if the information has any application to an anvil and hammer.  Back in the Seventies, a whole lot of knowledge was created that has little to do with reality.  Here's what I do know:  I have four anvils.  I started with a 600 Lb anvil, went to a 400 Lb anvil, then to a 218 Lb, than I bought a 100 Lb anvil.  This last has become my main use anvil, the rest collect dust.  I routinely forge 1 1/8 on my 100 Lb anvil without feeling that it's undersized.  As I have no power hammer, everything I forge is done on that anvil.  I am a full-time smith, the mortgage is paid by what I forge.

 

This is really interesting Gerald. Why do you prefer the smaller one, notwithstanding moving it around if needed? 

[Gerald Boggs]

Okay, Gerald, how big IS your hammer? :o

Well, I use a variety of hammers, it all depends on what I'm doing, but I think you're asking about my main use hammer.  I use the heaviest hammer I can accelerate with accuracy and still use thought out the day.  It does me no good to use a heavy hammer if I can't accelerate it as well as a lighter hammer.  Folks I see doing that, just end up choking up on the handle.  Which sort of negates any advantage of more weight.

 

My current use hammer is 2.70 pounds for most work and I'm slowly progressing to a 3 Lb hammer.

[Gerald Boggs]

This is really interesting Gerald. Why do you prefer the smaller one, notwithstanding moving it around if needed? 

Trust me, I'm pretty strong, I can not only move the 600 around the shop, I've twice loaded it in the back of a pickup truck by myself (not fun)  Of course, I don't pick the whole thing up at once.

I use the smaller for several reasons:
The rebound on the 100 is better then the 600.  That results in more work, less effort. 
The horn on the 600 is so large as to not be much use for the type of work I do. 
The width of the 600 makes forging items like Suffolk latchs and door pulls difficult.  Once I've worked one end and go to the other, I can't get the right angle because the anvil blocks me.   7 vs. 3 1/2 inches
It's easier to forge weld odd shaped pieces, the face doesn't get in the way.
Having said that, if I was forge welding large flat pieces, I prefer the 600.  It's like a table, lots of support for the bits sticking out.

I do use the 600 when photographers come by, makes a pretty picture.

[anvil]

something tells me that the relative difference in mass of a 125# noname and a 1000# anything else both securly attached to the earth, is a huge amount of decimal places to the right.

the proper weight for your normal work is the one you are most comfortable with. the primary modifiers are experience and age.

when your fav hammer quits moving what you are striking, follow that sage advice from that wise ole blacksmith:

"get a bigger hammer"

the above follows the KISS principal as close as possible.



the above does not apply to power hammers, as do most of the references in this thread

[dbrandow]

I am not a physicist, but I find myself skeptical of some of the physics and math that has been presented in earlier comments. Specifically, I am skeptical because it doesn't discuss the compressive strength of the anvil. The anvil isn't moving (assuming its anchored reasonably well), so the key factor is how much the anvil compresses underneath the blow (before returning to its original state), something that obviously isn't visually apparent. If we were to use some of the earlier formulas, a 100lb anvil made of rubber would behave the same way as a 100lb anvil made of steel, which is obviously ludicrous. The difference is that rubber compresses dramatically further under the same force than steel does. The mass and geometry of the anvil also matter, a 1lb 14 gauge piece of steel sitting on a piece of rubber will compress dramatically more under the same force than a 100lb steel anvil sitting on the same piece of rubber will.

[HWooldridge]

Rubber would also catch fire pretty quickly...<LOL>

[Francis Trez Cole]

Newton's second law apply's to hammering.


Newton's second law of motion can be formally stated as follows:

The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object.

anvil weight is irreverent. Take a piece of hot metal and hit it with a hammer the measure the amount of impact in the form of compression you have. Here is an other thing to think about if you want to move more metal faster place a bottom fuller in the hardie hole now take the same piece of hot metal hit it measure the impact compression. the anvil has not changed. So it is the dimension of the surface under the face of the hammer that has the most impact.

[K. Bryan Morgan]

There have been some very interesting comments on here that teach a lot.  I don't have any practical knowledge on this subject but I do have some experience with a light weight anvil. 

 

A couple of years ago I made an axe on a 25 pound anvil with a 2.6 pound hammer as the main forging hammer.  The work went smoothly and Jake and I experienced no issues with anvil or hammer weight.  With in a few hours, spread over several days, we had a nice camp axe.  The weight of the hammer, in my mind, was more important than the weight of the anvil.  I know this is anecdotal evidence, but my experience none the less.

[Gerald Boggs]

when your fav hammer quits moving what you are striking, follow that sage advice from that wise ole blacksmith:

"get a bigger hammer"

the above follows the KISS principal as close as possible.
 

The problem is that blacksmith might not have been so wise.  Getting a bigger hammer just wears you out. 

Acceleration with accuracy is for more useful than trying to use a bigger hammer.  I know I'm stronger then Peter Ross.  So how come, with a lighter hammer then I use, Peter is able to move twice the metal?  I've watched him do in two heats things I know would take me four-six heats.  Why?, Because Peter is able to accurately swing his hammer under acceleration and is able to do it better then I.   So better advise might be "Learn to use your tools"

[dbrandow]

anvil weight is irreverent. [...]

 

Again, intuitively that doesn't make much sense to me. Take a 100lb anvil, put it on a piece of rubber, now hammer a piece of hot steel on it. Repeat the experiment, but replace the 100lb anvil with a 1lb piece of 14 gauge steel. Think you'd have the same experience? Then anvil weight obviously matters, at least to some extent.

[Francis Trez Cole]

dbrandow first why would you want to put an anvil on a piece of rubber that dose not make any sense. The whole goal it to make the anvil,stand,and earth one.

Gerald You are so right Peter Ross is very accurate. He defiantly uses newtons law as an art form.

[bikecopXXX]

It's complicated. Simplify it. What feels the best? A hit that doesn't come back at all, cause all the energy went into moving yellow metal. Yeah. If it bounces back you didn't move any metal. If the anvil moves much, same result. And the anvil does move, even if you bolt it to the earth. The earth is a relatively soft spring.

[WayneCoeArtistBlacksmith]

I think that the thought of ratios comes from the power hammer comments above and some have taken it out of context, 

[Frank Turley]

Sliding off topic a bit, I think Gerald Boggs was getting into an area that leaves the ratio theories partially in the dust. I'm talking about the shape of the anvil and the skill of the worker. The 600 pounder was too big, too wide a face, too thick a horn or heel, for some things. The bickern was in many early shops, especially in Pennsylvania and Ohio, because the London Pattern anvil "needed help." A smith could often do better on the bickern's pyramidal horn and its narrow face.

 

Reference Peter Ross hammer acceleration, he is also highly skilled...can offset and fuller with the hammer face, among other things. He had a saying, "Make 50 of them; throw 45 away." I'm also minded of the old saying of George Ernest, an early California smith: "Some people hit it and watch where it goes; I know where it's going to go before I hit it."

 

Post Script. George Ernest began making farriers' tools for sale in 1946. He was especially known for his fine hoof nippers. His initials still accompany the present business, G.E. Forge and Tool Works.

[rockstar.esq]

Again, intuitively that doesn't make much sense to me. Take a 100lb anvil, put it on a piece of rubber, now hammer a piece of hot steel on it. Repeat the experiment, but replace the 100lb anvil with a 1lb piece of 14 gauge steel. Think you'd have the same experience? Then anvil weight obviously matters, at least to some extent.

 

Reading this I think you're confusing a couple points.  

 

First off one of the most frustrating things about learning physics is how damaging it is to intuition.  To "make the math work" you need to imagine the force of the hammer's blow downward being matched by a force from the anvil into the hammer.  If the reaction force out of the anvil is greater than it's mass times gravitational pull - it'll jump (or try to).

 

Anyone who's hammered a dime on concrete knows the dime jumps and the concrete stays still.

 

Efficiency in this case is going to be all about getting 100% of the force transferred into the stock without any rebounded energy.

 

Because hammers are heavy and we're working by hand it helps us to trade perfect efficiency for hammer rebound.  The ratio of hammer to anvil mass seems to me to be more about the concern that the anvil will move about.

 

None of which is to say you don't have a point.  I think what hasn't been said so far is that "all things being equal" folks don't often move heavy anvils.  They tend to make very strong and secure mounts for them.  Lighter anvils like farrier's use are often mounted less securely.  Mounting any anvil on a rebounding surface is unlikely to benefit it.  

 

Mass as a single factor is a fairly poor indicator of anvil performance.

[thingmaker3]

A blacksmith and an engineer walk into a bar...

[John McPherson]

......they should have ducked!

[Glenn]

Very good reply John LOL

[evfreek]

...

 

It sounds like there is a part 2 to the paper that is not included...any idea about that?

 

One thing he doesn't address is anvil geometry. A bigger anvil has a bigger sweet spot generally, but that sweetspot is even bigger if the waist is thick, as someone else noted.  Only mass directly in the shear cone under the hammer is fully effective.  That's why simple anvils of vertically oriented rail track and round or square bar feel so good for their weight.   Humans are puny and a few percent efficiency is easily noticed.  The bits outside the shear cone (horns) are less efficiently coupled to the main cone and are effectively attached to it by springs. 

 

...

 

Hi Bikecop.  There is a second part to the paper, and this also includes the bibliography, which does make things more straightforward.  You are correct about the "chicken".  The analysis assumes a point mass.  This, as practical experience notes, is more efficient than an elongated object.  It is surprising, however, how little off center mass saps from the forging efficiency, but the loss grows as the square of the distance from the center of mass (left as an exercise to the reader).

[evfreek]

But is it a valid application of the math?  No where does it take into account securing the anvil to the earth.  In short, practical experience doesn't support his claims.

Hi Gerald.  The analysis assumes no contact between anvil and earth.  Thus, it produces an pessimistic answer (underestimate of efficiency).  Accounting for a connection is not trivial.  This calculation is significantly beyond the textbook applications of conservation of energy and momentum.  Before calculations of this type are made, the hammer-anvil impact force needs to be estimated.  This estimation will open the door to the above and other interesting statements, and will appear in the second and forthcoming parts of the paper.

 

A significantly simplified and more approachable set of articles is running in the CBA magazine as well as some other local publications.  As expected, they have attracted quite a bit of controversy, primarily due to the author's gaps in clarity and anticipation of the kinds of questions.  There should be another installment appearing soon, perhaps in the next issue.

[John B]

A blacksmith and an engineer walk into a bar...

 

and saw his reflection in the back of the bar mirror.

[dbrandow]

dbrandow first why would you want to put an anvil on a piece of rubber that dose not make any sense. The whole goal it to make the anvil,stand,and earth one.

Gerald You are so right Peter Ross is very accurate. He defiantly uses newtons law as an art form.

 

Quite obviously I wouldn't do that in reality, what I presented was a simple thought experiment meant to demonstrate that anvil size (and geometry) clearly do matter.

[evfreek]

I am not a physicist, but I find myself skeptical of some of the physics and math that has been presented in earlier comments. Specifically, I am skeptical because it doesn't discuss the compressive strength of the anvil. The anvil isn't moving (assuming its anchored reasonably well), so the key factor is how much the anvil compresses underneath the blow (before returning to its original state), something that obviously isn't visually apparent. If we were to use some of the earlier formulas, a 100lb anvil made of rubber would behave the same way as a 100lb anvil made of steel, which is obviously ludicrous. The difference is that rubber compresses dramatically further under the same force than steel does. The mass and geometry of the anvil also matter, a 1lb 14 gauge piece of steel sitting on a piece of rubber will compress dramatically more under the same force than a 100lb steel anvil sitting on the same piece of rubber will.

No need to be skeptical.  Just understand the limitations of the simplified analysis.  The paper considers a freely suspended anvil (not anchored).  All the lost energy goes into moving the anvil.  For the first calculation, full rebound, there is a hidden assumption of no anvil deformation, because a point mass cannot store energy in its deformation.  The similar is true for the second calculation, but with the empirical observation of the coefficient of restitution, the additional assumption is introduced that most of the deformation is in the target (hot metal).  This conclusion does not follow from the analysis!  It is an experimental observation from industrial forging processes.  That is why it is so annoying to have a missing bibliography.  Most industrial forging processes occur at e = 0.1 - 0.2.  This is much closer to full stick than full rebound.  Most beginners and finish forging processes are at 0.8 or worse.  These numbers can be searched on the Internet, but they are only tabulated for large industrial forging hammers.

[dbrandow]

Reading this I think you're confusing a couple points.  

 

First off one of the most frustrating things about learning physics is how damaging it is to intuition.  To "make the math work" you need to imagine the force of the hammer's blow downward being matched by a force from the anvil into the hammer.  If the reaction force out of the anvil is greater than it's mass times gravitational pull - it'll jump (or try to).

 

Anyone who's hammered a dime on concrete knows the dime jumps and the concrete stays still.

 

Efficiency in this case is going to be all about getting 100% of the force transferred into the stock without any rebounded energy.

 

Because hammers are heavy and we're working by hand it helps us to trade perfect efficiency for hammer rebound.  The ratio of hammer to anvil mass seems to me to be more about the concern that the anvil will move about.

 

None of which is to say you don't have a point.  I think what hasn't been said so far is that "all things being equal" folks don't often move heavy anvils.  They tend to make very strong and secure mounts for them.  Lighter anvils like farrier's use are often mounted less securely.  Mounting any anvil on a rebounding surface is unlikely to benefit it.  

 

Mass as a single factor is a fairly poor indicator of anvil performance.

 

I completely agree with your point about using intuition in math/science, at least generally.  But in some specific cases, I believe you can use intuition as a 'sniff test'.  Believe me, I do understand 'equal and opposite reaction', but I also understand, in my non-physicist way, the difference between a perfectly elastic collision and the inelastic collisions we see in the macroscopic environment we are typically interested in.

 

I suspect you are correct, that mass as a single factor is a poor indicator (although I'd be interested in seeing real math/physics that demonstrated this), but at the same time I'd be deeply suspicious of the notion that it has no effect whatsoever.

[dbrandow]

No need to be skeptical.  Just understand the limitations of the simplified analysis.  The paper considers a freely suspended anvil (not anchored).  All the lost energy goes into moving the anvil.  For the first calculation, full rebound, there is a hidden assumption of no anvil deformation, because a point mass cannot store energy in its deformation.  The similar is true for the second calculation, but with the empirical observation of the coefficient of restitution, the additional assumption is introduced that most of the deformation is in the target (hot metal).  This conclusion does not follow from the analysis!  It is an experimental observation from industrial forging processes.  That is why it is so annoying to have a missing bibliography.  Most industrial forging processes occur at e = 0.1 - 0.2.  This is much closer to full stick than full rebound.  Most beginners and finish forging processes are at 0.8 or worse.  These numbers can be searched on the Internet, but they are only tabulated for large industrial forging hammers.

 

In the case of that specific analysis, I think I'm far more skeptical of the applicability of its findings to the real world question than I am to its contents, given how different the scenario it envisages are from the one we are actually using.