“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, we 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 because the chisel or nail isn’t moved and the beater bounces off. But it’s the other end of the weight scale that causes problems so let us 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? 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 most humble and obedient servant, could use more of. However, maintaining one’s girlish figure is not adequate justification for using excessively heavy hammers in light of other factors we must also consider.
Besides the herculean strength of your mighty arm and the chisel’s durability, you should also consider the durability of your body. Swinging a hammer that is too heavy stresses muscles, tendons, and bone, stresses that can make the day long, the nights painful, and your work sloppy, if not now then certainly as you age. 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. A word to the wise. We will look at this more in the final post in this series.
Let’s consider the movement of the hammer and the flow of forces that result starting at the beginning. Accelerating the hammer towards nail or chisel initially takes energy and creates stresses on 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, 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, driving the nail so deeply the wood is damaged, or the chisel so deeply it cuts all the way through, or even binds in the wood, is not useful, but is a waste of time and energy that damages our work product and our bodies, and that harms precision rather than improves it.
These forces and the positive and negative results are easier to control if the hammer’s weight is balanced with our bodies, the nail or chisel, and the wood. Heavier is seldom better.
Another factor to consider is the nature of the object the beater is to beat. Nails are one such beatee, but they don’t have feelings while chisels do, so I encourage you consider your chisel when selecting a hammer weight.
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 that amateurs are accustomed to using 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.
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 look at some guidelines.
Oiirenomi & Mukomachinomi Chisels
For most commercially-available woods you are likely to cut with your oiirenomi chisels or mukomachinomi (mortise chisel), 180gm (6.5oz) is a good place to start when using narrower width chisels 18mm and less.
300gm (10.5oz) to 375gm (14oz) is probably good for wider chisels. BTW the standard carpenter’s hammer in Japan weighs 375gm (14oz), but this is too heavy for most precision work using oiirenomi in furniture, cabinets, and joinery work.
For the heavier atsunomi chisels from 12 to 24mm in width, 375gm (14oz) is usually a good weight.
For wider atsunomi chisels, 675gm (24oz) to 750gm (26oz) is good. Maybe as heavy as 937gm (32oz) for motivating wide 48-54mm chisels when cutting hard woods if you have experience, strong wrists, and speed is not important. Yes, within limits, 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.
We also have another series of posts in the batter box about making a handle for your hammer that fits your body and will work most efficiently for you. So let’s talk some more soon.
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