“All that is gold does not glitter,
Not all those who wander are lost;
The old that is strong does not wither,
Deep roots are not reached by the frost.
From the ashes a fire shall be woken,
A light from the shadows shall spring;
Renewed shall be blade that was broken,
The crownless again shall be king.
J.R.R. Tolkien, The Fellowship of the Ring
In previous articles in this series about hammers to use with our chisels, your most humble and obedient servant discussed the varieties of hammers and the types of faces suitable for using with our chisels. In this article we will examine not only hammer weights but other factors to help your chisel work go more efficiently.
Beater & Beatee
You can usually tell when a hammer is too light for the job because the chisel or nail isn’t moved much and the beater bounces off. But it’s the other end of the weight scale that causes more serious problems so let’s consider the case of too heavy hammers so we can bracket the Goldilocks weight: Not too heavy, not too light, but just right.
Some people like to use heavy hammers for striking chisels. 2~3-lb ox-killers are good for some jobs, but there are a few things you should consider before defaulting too such a heavy lump.
Is the impact force produced by a heavy hammer really necessary to drive a chisel? Too often not so much. But not everything we do must focus exclusively on efficiency: swinging a hammer is good exercise and it burns calories, something those with excess “ dignity,” such as your humble servant, could use more of. However, in light of other factors discussed below, I urge you to resist the natural compulsion to remain one of the “beautiful people” by maintaining at all costs a sylphlike figure worthy of Paris Fashion Week by obsessively using overly-heavy hammers. Relax, for you already look mahvelous, darling, absolutely mahvelous!
Besides the herculean strength of your mighty arm and the chisel’s durability, Gentle Reader should also consider the durability of your body. Swinging a hammer that is too heavy can over-stress muscles, tendons, bones and joints, stresses that can make workdays long, nights painful and your work sloppy, if not now then certainly as you age. More on that subject in a future article.
But if the weight of the head is a good balance with the work you are doing, and you have a good handle on your hammer or gennou, things just go better. We will look at this more in the final post in this series.
Let’s start at the beginning and consider the movement of the hammer and the forces generated when accelerating it towards nail or chisel and the resulting stresses produced in muscles, tendons, bones and joints. Obviously, it is wise to keep these stresses within acceptable limits, especially if you need to repeat this movement hundreds or even thousands of times in a day. It should likewise be obvious that a hammer that is overly heavy makes limiting these stresses difficult.
Now that we have the hammer moving, let’s examine what happens when it stops as it strikes nail or chisel. Is wacking the nail or chisel as hard as possible the goal, or is the goal to drive the nail into the wood the right depth, or to motivate the chisel to cut wood an appropriate distance? If the latter, then there is a practical limit to the impact force required.
In other words, does driving a nail so deeply the wood is damaged unnecessarily, or does wacking a chisel so hard it cuts all the way through the board, or even binds in the wood, help us do better work?
Are the excessive stresses and vibrations flowing and slamming through one’s joints and tendons as a result of the violent acceleration, deceleration and impact forces generated when swinging an overweight hammer healthy and helpful? Or do they just waste energy, damage our work product, cause bruising, pinching, grinding and numbness and generally wear out hands and arms? Do these excessive stresses and vibrations improve our precision?
The positive and negative results of using a hammer are easier to control if the hammer’s weight is balanced with our bodies, the nail or chisel, and the wood.
Another factor to consider is the nature of the beatee. Nails often suffer from hammer abuse, but they don’t have feelings or form mutual support groups with monthly meetings and free coffee and donuts, while chisels do, so I encourage you be sensitive to your chisel’s needs when selecting a hammer weight. Oh, and don’t forget to donate a box of fresh donuts occasionally (with sprinkles).
Our chisels are hand-made professional-grade tools intended to be used by craftsmen who demand the extra sharpness and cutting longevity only hard, fine-grained steel makes possible. Therefore they are not as tough as the soft, sharpened Chinese screwdrivers sold by the big corporations as chisels that amateurs are accustomed to nowadays. Accordingly you should select a hammer weight that won’t damage the blades or splinter the handles of your fine chisels even if you must use them all day for days on end hard enough for the impact forces to make the handles hot. You may be as strong as John Henry, but a 2-lb hammer will destroy most any chisel given time and determination.
Weighty Matters
Of course, the harder the wood, the deeper the cut, the wider and heavier the chisel, the heavier the hammer needed. But what is an efficient hammer weight? Let’s consider some guidelines.
Oiirenomi & Mukomachinomi Chisels
For most commercially-available woods you are likely to cut with your oiirenomi chisels or mukomachinomi (mortise chisel), 260gm/9oz/70monme is a good place to start when using narrower width chisels 18mm and less.
300gm (10.5oz/80monme) to 375gm (14oz/100monme) is probably good for wider chisels. BTW the standard carpenter’s hammer in Japan weighs between 375gm (14oz/100monme) to 450gm (16oz/120monme), but this is too heavy for most precision work using oiirenomi in furniture, cabinets, and joinery work.
Atsunomi Chisels
For the heavier atsunomi chisels from 18mm to 24mm in width, 375gm (14oz/100monme) ~ 450gm (16oz/120monme) is usually a good weight.
For wider atsunomi chisels, 675gm (24oz/180monme) to 750gm (26oz/200monme) is good. Maybe as heavy as 937gm (32oz/250monme) for motivating wide 48-54mm chisels when cutting hard woods if you have experience, strong wrists, and speed is not important. Yes, within limits and with a good handle, lighter weight hammers tend to accomplish more work quicker.
As Captain Barbossa explained the Pirate’s Code, these are “more what you’d call “guidelines” than actual rules.”
In future posts in this series we will examine factors such as how to use hammers and chisels efficiently, and how to avoid injuries.
Until then, I have the honor to remain,
YMHOS
PS: We have also published another series of articles about making a handle for your hammer that fits your body and will work most efficiently for you, beginning HERE. So let’s talk some more soon.
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