Mounting an anvil??

[Peppie]

So I am just getting started in the hobby, and would like some advice.
I plan to do some forgeing, so I thought I would get a good foundation started. I came across a log. I tis 24'' across and 48'' long. I dug a hole and sank 24'' of it into the ground. (serious mass) Here comes the question.
I bought a 12'' length of Rail track. (it is temporary. budget is tight).
Is there any advantage to mounting it vertical as opposed to horizonal because of the mass it is mounted to??

 

[Knight Owl Forge]

This is often a heated debate on many blacksmithing forums, but I have seen videos where they do a side-by-side comparison and the results are very close in terms of rebound. You will gain a tad rebound by mounting it vertically (~5%), but by doing so you are losing a ton of surface area (~75%) and a shape that makes more sense as the top of an anvil. Rebound has a more to do with mass and composition/manufacturing of materials. So, when I first started and used a track anvil, I opted for the more surface area over the minimal gains in rebound. More specific to bladesmithing, it is nice to have a long flat surface for forging blades because it can help straighten and do other tasks. On a good piece of track mounted correctly, you should experience around 50% rebound give or take. That is much better than a lot of ASOs out there like the harbor freight one. They are also decently hard, so they should stand up to more abuse than a cast iron ASO.

 

[Peppie]

TY for the info.
I should have stated that it will be used mainly for Knife making

 

[JTknives]

This is often a heated debate on many blacksmithing forums, but I have seen videos where they do a side-by-side comparison and the results are very close in terms of rebound. You will gain a tad rebound by mounting it vertically (~5%), but by doing so you are losing a ton of surface area (~75%) and a shape that makes more sense as the top of an anvil. Rebound has a more to do with mass and composition/manufacturing of materials. So, when I first started and used a track anvil, I opted for the more surface area over the minimal gains in rebound. More specific to bladesmithing, it is nice to have a long flat surface for forging blades because it can help straighten and do other tasks. On a good piece of track mounted correctly, you should experience around 50% rebound give or take. That is much better than a lot of ASOs out there like the harbor freight one. They are also decently hard, so they should stand up to more abuse than a cast iron ASO.

The track will work fine for something to beat on. The lack of rebound is not a big issue considering Rebound means just about nothing when it comes to forging. You need mass under the hammer and rebound just tells you the mass is solid and that its hard so it wont wear out. But in all practicality, rebound does not make it easier to forge. Think about it, you want your energy to go into the hot steel. If the rebound helps "bonce" the hammer back up then your steel is to cold. Im not saying don't worry about rebound, Mass is most important.

 

[Knight Owl Forge]

If the rebound helps "bonce" the hammer back up then your steel is to cold.

Actually, rebound is quite important in a proper anvil... If it wasn't, people wouldn't have developed a way to test rebound, or testing for rebound wouldn't be the first thing they do when they look at a new anvil. Also, the best anvils wouldn't have the highest rebound ratings if it wasn't important. Rebound is important because it signifies how efficiently the anvil is opposing the force of the hammer. Rebound doesn't have anything to do with 'bounce' of the hammer or whatever (though that is a common misconception, even among guys that have been making knives for a long time), it has to do with Newton's Third Law, which states that each and every action has an opposing, equal reaction. In this case the action is hitting the anvil or piece with the hammer. The rebound indicates how much of that energy is being reflected back into the work piece. If the rebound is low, the anvil is not returning as much energy into the piece, which results in the slower, uneven moving of metal....

The best way to describe why its important is in this case: If you take a piece of square bar and taper the end by hitting a side, turning it 90 degrees and hitting the other side, you should be able to accomplish an even taper if the rebound is high enough... If not, your taper becomes lopsided, because the hammer is deforming the metal, but the anvil isn't nearly as much. That means with a low rebound anvil, you'd have to flip the piece to all four sides to make it even... This takes longer to do.

Ultimately, the bottom line is that rebound is very important to people who blacksmith daily. If you're swinging your arm all day long, you want the best rebound an anvil can provide, because even if realistically, a proper anvil saves you 10% of the swings in a day because it's high rebound (efficiency), then it's totally worth it. If you are forging one knife a month like most guys here, then it doesn't really matter.

 

[Stacy E. Apelt - Bladesmith]

To complete the above, the way to increase the reflected force is to increase the mass below the hammer. That can be done by putting the track endwise, getting a larger anvil,or putting more mass under the anvil. Welding the RR track ont a piece of 1" plate, a big barbell weight, otr setting it in a 20 gallon tub of cement will all increase the reflected force.

One common method is getting a #10 washtub and filling it with quikrete. Set the anvil on the top of that tub with some support boards so it only sinks in up to the base rail rim ( about 3/4"). This will keep the track from bouncing around. Orient the two tub handles so they are inline with the anvil ends, and use them to hold hammers as well as move the tub.

 

[Knight Owl Forge]

That can be done by putting the track endwise,

I agree that mass has large impact on the overall performance of an anvil (thinking of the equation for Newton's third law, where mass is an integral part of it), but I think there is this misunderstanding that mounting a track anvil on end will dramatically increase the rebound (the overall mass of the track remains unchanged). While there is a slight increase in rebound, the gains is nearly negligible in the grand scheme of things. That is why I advise mounting it horizontally. Instead of trying to explain it myself here is a video, which proves that the gain in rebound is minimal, while the loss in surface area of the anvil is dramatic. The video also clearly and correctly explains why rebound is important.

 

[Stacy E. Apelt - Bladesmith]

No, the mass is much more concentrated under the rail anvil surface when mounted on end.
Take a one square inch spot. Horizontal, there is about 6" under that spot, this there is 6 cubic inches of the mass. On end a 24" piece of that track has 24" under the 1 sqin spot, thus it has four tines the mass under the hammer.

The problem with mounting it on end is it offers a rather small forging area. Thus, increasing the mass under the anvil is the better option.

I have a 125# anvil sitting on an antique 400 pound acorn table as a base. This puts a lot more mass under the anvil base. It works like it was a 300# plus anvil.

 

[JTknives]

Actually, rebound is quite important in a proper anvil... If it wasn't, people wouldn't have developed a way to test rebound, or testing for rebound wouldn't be the first thing they do when they look at a new anvil. Also, the best anvils wouldn't have the highest rebound ratings if it wasn't important. Rebound is important because it signifies how efficiently the anvil is opposing the force of the hammer. Rebound doesn't have anything to do with 'bounce' of the hammer or whatever (though that is a common misconception, even among guys that have been making knives for a long time), it has to do with Newton's Third Law, which states that each and every action has an opposing, equal reaction. In this case the action is hitting the anvil or piece with the hammer. The rebound indicates how much of that energy is being reflected back into the work piece. If the rebound is low, the anvil is not returning as much energy into the piece, which results in the slower, uneven moving of metal....

The best way to describe why its important is in this case: If you take a piece of square bar and taper the end by hitting a side, turning it 90 degrees and hitting the other side, you should be able to accomplish an even taper if the rebound is high enough... If not, your taper becomes lopsided, because the hammer is deforming the metal, but the anvil isn't nearly as much. That means with a low rebound anvil, you'd have to flip the piece to all four sides to make it even... This takes longer to do.

Ultimately, the bottom line is that rebound is very important to people who blacksmith daily. If you're swinging your arm all day long, you want the best rebound an anvil can provide, because even if realistically, a proper anvil saves you 10% of the swings in a day because it's high rebound (efficiency), then it's totally worth it. If you are forging one knife a month like most guys here, then it doesn't really matter.

I'm sorry but I don't buy it. Since you went to the physics we will use that to explain it. The ball bearing test is a test of an elastic collision where kinetic energy and total momentum are conserved. Its not a perfect elastic collision hence the ball bearing not returning to its dropped height. but as soon as you introduce a softer material into the system it goes from an elastic collision to an inelastic collision. The softer the material is between the hammer and anvil the more inelastic the collision becomes. With an inelastic collision total kinetic energy is not conserved but total momentum is. This kinetic energy is absorbed into the softer material which gives us heat, sound, deformation exc. Because we are now dealing with an inelastic collision our hammer and anvil just need to be hard enough to not add to the inelastic system. This means The anvil and hammer need to be harder then the squishy bit in the center. If the hammer or anvil are able to be deformed by the hot metal then we loose kinetic energy into those and not into the the item we want. This would in fact require more work to be put into the system then if only the center item was absorbing the kinetic energy. But remember in an inelastic system total kinetic energy is not conserved but total momentum is. This is where the ratio of hammer mass to anvil mass comes into play. To calculate this its the mass and velocity of the hammer plus the mass and velocity of the anvil. This is assuming a perfect inelastic collision like a car crash.
mv(hammer) + MV(anvil) = (m+M)V where V is final velocity.
This gets simplified down to (m*v+M*V)/(m+M)
You can quickly see that as the mass of the anvil increases the resulting final velocity drops. This also comes full circle back around to anvil mounting and why its important. lets do a simple math calculation to demonstrate this. Say our hammer weighs 3lbs and our anvil weighs 100lbs. Say we drop our hammer from 3ft this will end up hitting the anvil at 9.5 mph. This gives us these numbers
(3lb*9.5mph+100lb*0mph)/(3lb+100lb)=28.5/103=.28mph
This means when the hammer hits the anvil everything wants to move towards the ground at .28mph. So if we have a crappy mounting for our anvil then this mounting will absorb this. As soon as we mount it properly we have basically increased the mass of the anvil to a MUCH higher number which drops the final velocity and puts more energy into the workpiece.

I will let trent explain it better then I did

 

[Knight Owl Forge]

What I am getting at is that the overall mass of the object is more important that the mass under the impact zone of the hammer. Let's say we were to measure the difference between the mass under the impact zone on a horizontal track and a vertical track. Let's say the mass under the impact zone on the vertical one is four times greater than the horizontal one... If rebound relied heavily on mass under the impact zone, you would should see a major increase in rebound by mounting it vertically. However, the video I posted above clearly shows that this is not the case. The dramatic increase in mass under the impact zone seems to only increase the rebound by 5%. Ultimately, I think rebound is more closely effected by overall mass, material composition, construction methods, mounting, and a bit by hardness.

 

[Knight Owl Forge]

I'm sorry but I don't buy it. Since you went to the physics we will use that to explain it. The ball bearing test is a test of an elastic collision where kinetic energy and total momentum are conserved. Its not a perfect elastic collision hence the ball bearing not returning to its dropped height. but as soon as you introduce a softer material into the system it goes from an elastic collision to an inelastic collision. The softer the material is between the hammer and anvil the more inelastic the collision becomes. With an inelastic collision total kinetic energy is not conserved but total momentum is. This kinetic energy is absorbed into the softer material which gives us heat, sound, deformation exc. Because we are now dealing with an inelastic collision our hammer and anvil just need to be hard enough to not add to the inelastic system. This means The anvil and hammer need to be harder then the squishy bit in the center. If the hammer or anvil are able to be deformed by the hot metal then we loose kinetic energy into those and not into the the item we want. This would in fact require more work to be put into the system then if only the center item was absorbing the kinetic energy. But remember in an inelastic system total kinetic energy is not conserved but total momentum is. This is where the ratio of hammer mass to anvil mass comes into play. To calculate this its the mass and velocity of the hammer plus the mass and velocity of the anvil. This is assuming a perfect inelastic collision like a car crash.
mv(hammer) + MV(anvil) = (m+M)V where V is final velocity.
This gets simplified down to (m*v+M*V)/(m+M)
You can quickly see that as the mass of the anvil increases the resulting final velocity drops. This also comes full circle back around to anvil mounting and why its important. lets do a simple math calculation to demonstrate this. Say our hammer weighs 3lbs and our anvil weighs 100lbs. Say we drop our hammer from 3ft this will end up hitting the anvil at 9.5 mph. This gives us these numbers
(3lb*9.5mph+100lb*0mph)/(3lb+100lb)=28.5/103=.28mph
This means when the hammer hits the anvil everything wants to move towards the ground at .28mph. So if we have a crappy mounting for our anvil then this mounting will absorb this. As soon as we mount it properly we have basically increased the mass of the anvil to a MUCH higher number which drops the final velocity and puts more energy into the workpiece.

What don't you buy exactly? You said that rebound isn't that important, to which I responded by saying that rebound is in fact important because the higher the rebound, the faster you can move metal. I have forged on various anvils of varying mass, composition, hardness, rebound and so on... The anvils with the highest rebound and mass have shown to move metal at a faster pace. Looking at Newton's third law, it makes sense.

 

[JTknives]

What i was trying to say is that rebound does not mater to an extent. Think of rebound as a spring on your anvil. You drop your hammer on the anvil and the spring compresses. The spring converts kinetic energy into potential energy which it then releases back into the hammer pushing it back up. This is an elastic collision where kinetic energy is conserved, its Newton's third law. The hammer and surface of the anvil act as springs upon each other. Thy store the kinetic energy and push back creating rebound. It all comes down to this one simple principle and that is Yield strength. We all know that hardness does not change the stiffness of a steel or how much it will flex with x weight. What hardness does do is increases its yield strength so it can flex further with more weight before it deforms plastically. We all know this when it comes to knives but it also applies to our hammers and anvils. We drop the hammer on the anvil and the surfaces compress and as long as we don't exceed the yield strength of the hammer or the anvil we will not dent them. Once you hit it hard enough that your exceed this number you deform the surface and create a dent. The reason dropping a ball bearing on different steel surfaces have different rebounds is because of this same principle. Softer steel plastically deforms under the dropped ball which moves us further down the elasticity chart into a greater inelastic state. The kinetic energy of the ball is absorbed by the small dent it made when it exceeded the yield strength of that steels surface. As we make the surface harder and harder the steel has a higher yield strength which dents less which absorbs less kinetic energy. What I'm getting at with all this is one simple fact. As long as the hot steel has lower yield strength then the hammer or anvil it will deform and absorb the kinetic energy. The hammer and anvil just like a knife have a set yield point depending on there hardness. As long as we don't exceed this number the anvil will preform just as good as one that is much harder. This is because we know that making something harder does not make it stiffer. Mass on the other hand plays a big roll, the higher the mass the more energy it takes to move it. If your moving your anvil with every strike then energy is being wasted. Mass makes things stiffer so standing a track on end is a stiffer orientation then laying it down. I will go out on a limb and say that mass its self affects rebound very little. You just need enough to provide stiffness to the material under the dropped ball. This is why mass does not mean greater rebound.

 

[RayseM]

I am loving this thread though I don't have any need for an anvil.

BF rocks - er - BOUNCES - yeah, that's it, BF bounces

Ray

 

[Peppie]

So I made an 18'' long anvil out of a piece of #141 rail. I am getting ready to mount it. Is it better to get a 48'' X 24'' log, dig a hole 24'' deep and drop the log in there. (A lot of work) Or will I notice a big differance if I were to just screw it to a 20'' tall X 24'' diam. Log just sitting on the ground?

 

[Stacy E. Apelt - Bladesmith]

As said, the more mass under the anvil, the better. However, with a RR track anvil, I think your 20" log will be fine.

Knight Owl,
To show the error in your logic, let's take it to the extreme. A piece of steel 4X8X6" weighs about 50 pounds. A strip of sheet .125X8 and 200 feet long weighs 50 pounds. Obviously, forging on the thicker block will be more efficient than forging on the 1/8" thick sheet .... even though they have the same mass.

 

[Knight Owl Forge]

Stacy,

I didn't say that shape of the anvil doesn't have ANY impact on the rebound, just that when you move from a horizontal mounted track to vertical track that the gains are marginal compared to loss of surface area. If you plotted rebound as a function of anvil shape from least ideal to most ideal, it would be a curved graph, meaning that when you move around in the middle of the curve (horizontal to vertical mounting of a track for example), not a lot of change happens in regards to rebound.

JTKnives,

While I agree that hardness plays a role in rebound that isn't always the case. For example, some of the cast Russian anvils that are notoriously soft can produce higher rebound than anvils that have harder faces. You talk about yield strength in hot steel and that if it is less than the anvil and hammer, then the rebound of either of those doesn't matter... Well, to a degree you are correct, but a LOT of the energy you are imparting on the piece on the anvil transfers through the piece to the anvil below. If that anvil seriously lacks rebound, it will not be able to return some of that energy back to the piece. Again, I never claim that a 20% increase in rebound equals a 20% increase in efficiency, and that is because a lot of energy is placed into deforming the metal like you describe. I'd say a 20% increase in rebound would probably net you less than 5% gains in overall efficiency. So based on that assessment, I would say the 5% increase in rebound by mounting a track vertically will return less than 1% efficiency, and that is trading away like 70% of the surface area!

 

[Randy3000]

As a man that holds degrees in math and physics, i just have to wonder, how hard can it be to just try both and see for yourself? The real world experience and determining yourself you are doing it the best way has to be far superior and much more personally meaningful than any scientific reasoning.

 

[Atlas Knife Company]

My golf clubs have more rebound than my anvil. That doesn't make them a better anvil. Furthermore, surface area isn't as important for knifemaking as it is for blacksmithing.