Which mallet and why

[Tom Bender]

When selecting a mallet to drive a chisel, weight is important. Let's look at the math without going deep.

There are two assets a mallet can bring to the work, Energy and Momentum.

Energy = Mass times Velocity squared. Energy = M V V (neglecting the constant 1/2 for this non numerical discussion)

Momentum = Mass times Velocity. Momentum = M V

Now let's go to the shop for an experiment. We'll cut across the grain.

Lets hit with a light and fast mallet, high energy. Fibers are cut but not deeply.

Now a heavy slow mallet, velocity is less important. More fibers are cut. Hmmm why is that?


I believe this can be understood without invoking integral calculus but have hit a wall here.

[Kent A Bathurst]

Now a heavy slow mallet, velocity is less important. More fibers are cut. Hmmm why is that?

You live outside the path of the annular eclipse, which would have provided counteracting balancing forces.

Or maybe your arm-swing delta-V is not correct in terms of the delta-M.

But I still think its the eclipse.

[Edward Weber]

When selecting a mallet to drive a chisel, weight is important. Let's look at the math without going deep.

There are two assets a mallet can bring to the work, Energy and Momentum.

Energy = Mass times Velocity squared. Energy = M V V (neglecting the constant 1/2 for this non numerical discussion)

Momentum = Mass times Velocity. Momentum = M V

Now let's go to the shop for an experiment. We'll cut across the grain.

Lets hit with a light and fast mallet, high energy. Fibers are cut but not deeply.

Now a heavy slow mallet, velocity is less important. More fibers are cut. Hmmm why is that?


I believe this can be understood without invoking integral calculus but have hit a wall here.

When selecting a mallet to drive a chisel, I pick it up and judge the weight.

You also need to consider inertia

[Eric Brown]

When selecting a mallet to drive a chisel, I pick it up and judge the weight.

You also need to consider inertia

I prefer Wood-Is-Good urethane mallets. I make better contact, it's slightly quieter, and it's easier on my hands.
Also, how the weight is distributed in the mallet matters. Too much weight in the handle reduces strike force at the head.
Don't even consider the aerodynamics of the different head shapes.

[Reed Gray]

Well, it is like hammers. What are you hitting? Bigger hammers for driving splitting wedges, smaller hammers for driving finish hails. I have 2 mallets, one sugar maple and one persimmon. The maple is the lighter one, the persimmon is pretty heavy. I also have a small hammer with a mountain mahogany head. I use it for adjusting plane irons with very light taps. It just depends on the job.

robo hippy

[Tom M King]

12, 18, and 30 oz. Wood is Good ones here. I just pick a small one for small chisels, and a big one for big chisels.

[Jimmy Harris]

There's too many factors to be worth your time to consider the mathematics of it all. Like, the mallet it a fulcrum, so the longer the mallet (or further back from the strike zone that you hold the mallet), the faster the head travels, assuming you're using it as a fulcrum and not just dropping it straight down. Which brings into the overall equation body mechanics and how different designs will change your swing. Plus there's the hardness and rebound of the surface being struck to consider. Generally, the harder the mallet face, the more energy will transfer to the chisel. Then you've got wind resistance to throw in there.

It's best to just use experimentation and find out what works best for you. Personally, I like heavier mallets. Let the mallet do the work for you by way of gravity and you can adjust the force applied as necessary by adjusting the starting distance between the mallet and chisel and the point of contact on the mallet. It's easier on my shoulders and arms as all I'm generally doing is lifting the mallet to drop it. To me, around 28-36 oz. is the sweet spot for a woodworking mallet. If I need less force than I can comfortably obtain with a 28ish oz. mallet, I generally don't need a mallet at all. About 5 lbs is the max for me. Beyond that, and I'd rather apply more force on the stroke than lift it repeatedly. Flat or round face doesn't matter to me. Making solid contact has never been an issue.

Everyone is different, so as long as it works for you, it works. I know a lot of people hate soft rubber mallets because of the rebound, but I like them for that reason. It gets them back into position easier and takes less effort. I also like my urathane Wood is Good 30 oz. mallet, though I wish the grip on the handle wasn't so long, as it's only really comfortable to hold near the top. But I like how it sits, handle up, on my bench, and doesn't wear out with use like my rubber and wooden mallets do.

[Edward Weber]

There's too many factors to be worth your time to consider the mathematics of it all. Like, the mallet it a fulcrum, so the longer the mallet (or further back from the strike zone that you hold the mallet), the faster the head travels, assuming you're using it as a fulcrum and not just dropping it straight down. Which brings into the overall equation body mechanics and how different designs will change your swing. Plus there's the hardness and rebound of the surface being struck to consider. Generally, the harder the mallet face, the more energy will transfer to the chisel. Then you've got wind resistance to throw in there.

Your elbow joint is the fulcrum, the mallet is the load on a lever.
vZVVxPlewswNBMmWhJ2ZDw.jpg

[Rafael Herrera]

Energy = Mass times Velocity squared. Energy = M V V (neglecting the constant 1/2 for this non numerical discussion)

Momentum = Mass times Velocity. Momentum = M V

Lets hit with a light and fast mallet, high energy. Fibers are cut but not deeply.

Now a heavy slow mallet, velocity is less important. More fibers are cut. Hmmm why is that?

Velocity is as important as mass. To simplify things, consider you're swinging the hammers at the same speed. Also, let's say the light hammer is 1 unit of weight and the heavy mallet is like 2.

The heavy hammer is hitting the chisel with twice the energy or momentum, as simple as that. You can't directly compare Energy and Momentum.

---

In any case, I looked up what the force exerted on the chisel is when impacted by the mallet. The formula for the Force includes the mass and the velocity squared.

So, if you are still swinging the heavy mallet at the same speed as the light mallet, then the applied force is twice that of the light mallet.

However, you just need to swing the light mallet around 40% faster (because of the square) to match the force of the heavy mallet.

---

I've simplified things somewhat, but I think I'm mostly right. I think the bottom line is that you need to swing a lighter mallet faster to match the effect of a heavy mallet swung slower. There's a point where a heavy mallet is just not as comfortable, so your arm strength is important to find the right balance of speed and mass.

Rafael

[Jim Koepke]

Leverage is another important factor to consider. As already said the further out the head is from the hand the larger the arc it must travel. If it travels the arc in the same time the head moves on a shorter handled mallet it is traveling at a higher velocity.

My two favorite mallets are the cherry mallet on the bottom and the hickory mallet on the right.

Cnerry & Hickory Mallets.jpg

They are about the same weight. The cherry mallet has a longer handle. It is my go to mallet when cutting a mortise.

jtk

[roger wiegand]

I use a small but heavy mallet-- I have a brass one and a maple one I turned and filled with lead (I prefer round mallets for most uses). Tap lightly for a small chisel or fine cut, whack it when using a big gouge to hog off wood. I find I have more control with the heavier chisel. I have a small urethane Estwing deadblow hammer that is also great for heavier work, unfortunately they discontinued it in favor of a much bigger, heavier model.

[Justin Allen]

All things being equal, a mallet that is mass M, moving at velocity V (which is a vector), and striking the chisel at the SAME angle as a mallet of mass = 2M and velocity 0.5V, will impart the same effect on the wood. The vector component is important, as glancing blows reduce the transfer of momentum to the chisel.

Finding the balance between mass and velocity (as Rafael said) that yields the optimum comfort and control will be the most effective at removing wood.

Kinetic energy in this application is misleading, because only a portion of that amount does actual work on the chisel. The contact angle is still applicable here as well, as work is the dot product of a force vector and path vector.

[Rafael Herrera]

The formula I found yesterday gives the impact force as a function of: mass, speed squared and the distance it takes the object to stop.

F = 1/2 * M * V^2 / d

​The distance "d" would be in our case the depth of the chisel cut into to wood. I assumed it was the same in both cases in my post. However, the point of the discussion is to analyze how much cutting the chisel will do when struck my the mallet, so the value of "d" is important.

Weight and speed of the mallet, and the chisel profile can be controlled. The value of d depends on the type of wood we're chopping, so we'll need an actual experiment to compare mallets.

[William Fretwell]

While increasing velocity is very effective at increasing the energy delivered it decreases control and aim. Miss hitting the chisel end can be unfortunate. Simply increasing the mass of the mallett maintains control while delivering more energy.

This does not prevent you from doing both of course. Beating the **** out of a timber frame chisel with the heaviest wood is good urethane mallet I managed to disintegrate the mallett. Had to collect all the little lead pieces all over the floor and the top to epoxy it all back together. The distance moved by the urethane delivering the energy does decrease the force, but the energy is delivered over a far larger area at the end of the chisel. The end of the chisel showed no distress even after hours of pounding.

[Michael Bulatowicz]

The formula I found yesterday gives the impact force as a function of: mass, speed squared and the distance it takes the object to stop.

F = 1/2 * M * V^2 / d

​The distance "d" would be in our case the depth of the chisel cut into to wood. I assumed it was the same in both cases in my post. However, the point of the discussion is to analyze how much cutting the chisel will do when struck my the mallet, so the value of "d" is important.

Weight and speed of the mallet, and the chisel profile can be controlled. The value of d depends on the type of wood we're chopping, so we'll need an actual experiment to compare mallets.

While not wholly incorrect, the picture painted above is incomplete (and is a linear approximation of the actually more-complicated mechanics). Further, "d" in this linear approximation is the distance the mallet head center of mass travels upon impact with the end of the chisel, not the depth the chisel penetrates into the wood. Without delving deeply into the math or physics (which I would be willing to do if you're interested) Justin is correct that momentum is more important than energy in this case, and that the energy perspective is misleading.

Kinetic energy is not conserved in a collision. Meaning, in this case, the kinetic energy does not all go into cutting the wood. Some goes into heat, some goes into sound waves, some goes into energy stored in residual stress in the materials involved: those materials do exhibit some permanent deformation. Some goes into temporary deflection of the materials, which spring back and push the mallet head back away from the chisel. None of that energy goes into cutting the fibers.

Momentum, on the other hand, is conserved in collisions--specifically, the total momentum of the system composed of the mallet, your arm, the chisel, the bench, etc.

A mallet with less momentum will cause the chisel to penetrate less deeply under otherwise identical circumstances, even if the kinetic energy is identical to that of a mallet with more momentum.