What is ergonomics? It is the science of fitting the workplace conditions and the jobs demands. It comes from the Greek ergon meaning work and nomics meaning natural law. It is the study of how we work and how it affects our body. How do we apply ergonomics principles in the workplace? There are 2 elements one is static work the other is force.
- Static- work refers to the musculoskeletal the effort required to hold a position.
- Force- refers to the amount of tension our muscles generate.
The risk factors are prolong excretion of the hands, heavy lifting, pushing, pulling, vibrations, cold and prolong awkward posture. The level of effect on the body comes from the intensity, frequency and the amount of time spent on the task.
"All work activities should permit the worker to adopt several different, but equally healthy and safe positions. Where muscular force has to be exerted the largest appropriate muscle group available should do it. Work activities should be performed with the joints at about mid-point of their range of movement. This applies particularly to the head, trunk, and upper limbs".(Corlett 1983)
The father of ergonomics is F. M. Alexander (1869-1955). He had lost his voice chronic laryngitis and as an actor that didn't fair well for him. So he developed a technique of stretching, which is a lot like Tai Chi, and that was the start of the study of ergonomics. It becomes a life style of movement.
- The neck should be free the head be forward from the spine.
- To allow the torso to fan open.
- Allow the legs to release from the hip joint.
- Allow the shoulders to release and hang on the rib cage.
Occupational Safety and Health administration (OSHA) has guidelines for ergonomics so lets look at them to see how hammering fits into them. Hand tools should have soft handles. The handle should not have finger groves. Handled should be angled.
Understanding the basic of ergonomics what are the key points to being a healthy and safe blacksmith.
- hammer head (style)
- anvil height
- body position (static and force)
We're looking at the types of handle we find that there are three wood, fiberglass and metal. It has been shown in a study by William Dvorak, Oliver Haas, Leif Jentoft and Adam Kenvarg | Olin College, February 2008 shows that the best hammer handle is fiberglass or steel with anti shock technology. This study bring to light that the vibration that happens when the hammer hits the anvil is damaging to the hand and wrist the low level vibrations is what dose the damage and it happens with in the first second after the strike. The new handles move the vibrations from the low frequencies to the high frequencies in less than a second. These handles are also soft in texture helping even more. It dose take an effort to get use to the new types of handles but the transition is worth the effort to have more protection for your body.
Well this is a personal thing and there are many factors in the mix. First if it is just the surface to hammer contact then your knuckles should just touch the face of the anvil. If you are using a guillotine tool in your harder hole then your knuckles should touch the top die when in place. Or a top and bottom swage tool that is hit by a hammer the same height should come in play. One of the options is to make anvils to hold guillotine or swage tools to the height you need. So having anvils at different heights is not a bad thing. It is not one height fits all.
Standing at the anvil your body position is very important factor. So lets look at a basic anvil London pattern as a blacksmith you want 2 types of edges on your anvil a soft (rounded corner) and a hard (sharp corner) one on each side. So to work these edges you have to stand on the side of the anvil. Your feet should be shoulder with apart and even with each other. Knees slightly bent and relaxed. Your hammer should land in the center of the face of the anvil. As a chef I taught new cooks motor skills and the example I used was I drew a line from corner to corner in a "X" on the cutting board one line of the X was the knife and the other line was your hand holding the food. Well the same applies to use of the anvil one hand holding the hammer and the other hand holding the stock to be forged. This basic stance helps with your shoulders giving your upper body variation. When you moving one foot forward to work the far side of the anvil or one foot back to work the near side is a good habit this changes you body alignment while keeping you in balance allowing you to have several positions which is good ergonomics. When you use a tool in you harder hole you want to stand at the heal of the anvil that way you are working over the tool and you can see it while you strike. While working the horn you should work on a diagonal this will give you more surface area and keep your stock from wanting to corkscrew as you draw it out. I feel the horn should be on the side that you feel most comfortable with I manly work with the horn on my left I am right handed. I have switched it to the right on occasion depending what I am working on. I like the shop to be mobile rather stationary most blacksmith use triangle (forge, anvil and vice) I like a half circle where I can add or take away tools as needed to fit the job at hand. Remember movement is energy used.
Your swing of the hammer, like a golf swing, can only get better by practice, practice, practice. So with all the movement your arm will do, how can we protect yourself? Lets start at the hand and work up from the point where the hammer hits metal. This is the method for a heavy hammer. Your grip should be loose on the handle. Your wrist should be straight elbow bent. Remember that a joint should be used only at 50% of its full range most blacksmiths work their elbow in the 75% range, which is ok. You do not want to be straight-armed or at less the 50%. There will be shock created from the impact of your hammer on the metal, which will bounce the hammer and help in the return for the next swing. This shock will also create vibration in the handle so to minimize this good handle selection is important. As your hammer bounces off the anvil you should bend at the wrist first then bend your elbow and rotate at the shoulder then extend you elbow and deliver the next strike. This way you will have a full range of motion using all muscle groups to move the hammer and reduce dependence on one muscle group. With good ergonomics in mind you should have different swings for different weights of hammers and different styles. No one system of swing a hammer is good for the body variation is the key to a good ergonomic balance.
The Hammer: Myth or Legend
written by Francis Trez Cole
I have been studying hammers and hammering techniques for some time now and some of the information I have found is very eye opening. Lets start with the type of hammers blacksmiths use. What is a hammer? It is a shaped lump on steel on the end of a wooden stick that you hit metal with in its simplest form. The shape of that lump varies in style from region to region, as well as personal style to ones vision of the work to be done and the desired outcome of the work. The debate will go on for years which type is best I am sure of that. The purpose of this article is to look at the hammers on the market what it dose and how it is used to move metal in our job. The effects it has on the metal and each and every one of us in the field.
I am sure there will be those who like their hammer better than other hammers on the market, good for you. If it works for you that is great. This will help new blacksmiths find a lot of information on hammers in one place so you can make up your own mind how best to invest their money to give them the best hammer for their dollar.
So what do you expect to do with your hammer? Move metal to a desired shape. Looking at the shape of hammers faces they are only two types flat or rounded.
There are many variations and combinations of these hammers faces. A German style, rounding hammer, cross peen, straight peen, Ball peen, Swedish style, French style, Dutch style, Japanese style, Scythe style, and Hofi style just to name a few. All have a flat and or round face to the hammer. The flat face of the hammer is to make smooth and flat marks on the metals surface the rounded part is designed to move the metal in a radiating shape or in a straight line to help move metal faster in a given direction. The blacksmith must choose the hammer, which best meets there needs.
Lets look at the Japanese style hammer first why to get it out of the way I feel its design is a shape of function it has a lot of mass on a short curved handle. Why, well that is simple, look at a samurai sword and the shape of the blade it is faceted; those facets run the length of the blade. As the blade smith works the shape of the blade the angle of the hammer falls on is in alignment to the blades facets. In the same shape is a dogface hammer used by file makers for the same reason he is always cutting on an angle.
So those are the exceptions now lets look at the rest of the hammers you can only hit a hammer 5 ways flat, toe edge, heal edge, right side edge and left side edge. The reason to hit a hammer on its toe the edge away from you is to move metal towards you. The heal of the face will move metal away from you and the right and left side edge will move the metal to the sides. The flat strike will clean up any strike marks and make the metal smooth. I see this as the Habermann method although others have claimed it as their own. The real question is where did they get the enlightenment to think of this.
What happens when you hit a piece of metal at the right temperature on an anvil with a hammer? The force of the hammer comes in contact with the metal and it has to spread it absorbs some of the impact. Then it gets to the point where it will not move any more. The hammer then has to recoil helping the hammer back up into the striking position. Managing this motion is the goal to get the most amount of work with the least amount of energy expended. This is where Newton's II law comes into play. The handle length needs to be the same length lets say 14". If you could swing a 50 pound hammer at 10 ft. per second you archive 500 foot pounds of force and if you could swing a 2 pound hammer 250 ft. per second it is lighter so you can move it faster you would create the same amount of force. A 50 pound hammer has a much larger face so the impact mark would cover more metal where the 2 pound hammer has a smaller face would make a deeper mark in the same metal. By no means do I want you to swing a 50-pound hammer unless you are a striker. Some farriers like a long handle with a light head some blacksmith like a short handle with a 32 oz. head or larger. Foot-pounds is a mathematical game it is deciding what will work best for you. Myself I like a hammer 2 pounds with a 14" handle. It gives me the option to swing at full length or to choke up on the handle for more controlled blows.
How lets look at the handle what are the 3 factors when considering type of handle yes I said type. There are three types of handle: wood, fiberglass, and metal. With these types we must look at shape and vibration conductivity. The purpose of the handle is to give you something to hold on to and to be able to steer the head of the hammer to the target. Shape a handle should be conical in shape smaller near the head of the hammer and larger where you hold it. I like a longer handle with 2 progressions so I can hold the handle in the middle or at the end to gain more velocity.
Vibration conductivity the vibration range that is produced from the hammer striking the metal on the anvil comes in 2 forms high and low frequencies. High frequencies go away fast and will cause very little damage to the hand, wrist and elbow. Low frequencies on the other hand are what cause the damage. The handle that transfers the low frequencies the best is wood. Yes, tests show that fiberglass and metal push the low frequencies waves out of the handle and they become high frequencies faster protecting the body better. I know this comes as a shock to me as well but the science is sound. For new smiths the hardest skill to learn is hammering. I bought one of each to see how they work and I was able to get use to the fiberglass faster. On the other hand I do like the feel of the metal handle. The great advantage of these hammers they can be bought at Lowe's or Home Depot for around $20.00. It is a great starting point for the beginning blacksmith and a great exercise for the experiencedAaå one. The face of the hammer will have to be dressed.
Years ago while working as a Chef there were many chefs that tried to convince new cooks that the $150.00-$400.00 knife was the way to go it will make them a better chef. But I believe that a $20.00-$30.00 knife was the way to start to learn how to use it and care for it and make the mistakes with. I think the same is true with blacksmithing. Then you can learn to make your own is another option as you gain experience.
So armed with this knowledge searching for a hammer starts we all have different size hands so you will find the one that fits you best. In holding a hammer as a smith you are guiding it to the target. Your hand should be wrap around the handle with a loose grip you fingers should not touch the base of your thumb. While you are swing if someone took hold of the hammer it should come out of your hand. As far as your thumb goes using it on top of the handle for light blows off anvil is fine like starting a scroll but heavy blows will damage the nerve in you hand. Next we will look at your stance and swinging the hammer the study of ergonomics. I hope this helps.
Learning to Blacksmith - Getting somewhere - YouTubewww.youtube.com/watch?v=28O_yYLi9Po
International encyclopedia of ergonomics and human factors - Google Books Resultbooks.google.com/books?isbn=041530430X
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