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by Francis Trez Cole
Posted 15 April 2011 - 01:41 PM
What is ergonomics? It isthe science of fitting the workplace conditions and the jobs demands. Ergon meaning work and nomics meaning natural law. It is the study of how we work and how it effects our body. How do we apply ergonomicsprinciples in the workplace. There are 2 elements one is static work the other is force.
Static- work refers to themusculoskeletal the effort required to hold a position.
Force- refers to the amount of tension our muscles generate.
The risk factors are prolongexcretion of the hands, heavy lifting, pushing, pulling, vibrations, cold andprolong awkward posture. The level of effect on the body comes from theintensity, 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 it should be done by the largest appropriate muscle group available. Work activities should be performed with the joints at about mid-point of their range of movement. This appliesparticularly 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.
1. The neck should be free the head be forward from the spine.
2. To allow the torso to fan open.
3. Allow the legs to release from the hip joint.
4. 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 handles hould 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.
2. hammerhead (style)
3. anvil height
4. body position (static and force)
Handle well 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 fiber glass or steel with anti shock technology. This study bring to light that thevibration that happens when the hammer hits the anvil is damaging to the handand wrist the low level vibrations is what dose the damage and it happens within 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.
The hammer head, see article “The hammer myth or legend”
Anvil height 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 hardie hole then your knuckles should touch the top die when in place. Or a top and bottom swedge tool that are hit by a hammer the same height should come in play. One of the options is to make anvils to hold guillotine or swedge 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 cork screw 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 you can only get good 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 there 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 of hammers. No one system of swing a hammer is good for the body variation is the key to a good ergonomic balance.
A fairly good report, overall. The subject of ergonomics and bodily movement is broad and should continuously be studied and have more material added. I have no statistics, but I think more money is pumped into Sports Medicine than Occupational Therapy, because there IS more money in that field. Some factors are difficult to evaluate. For instance, heritable traits. Not all of us are born with the punch of a Mike Tyson. Some of us have stronger skeletal frames than others. The same can be said for muscles, ligaments, tendons.
I have a nodding acquaintance with the Alexander Method. I would also suggest that other forms of exercise/stretch/movement be practiced in conjunction with smithing, such as yoga, tai chi, chi kung, sports stretches, and Feldenkrais micro-movements. Runners and athletes are familiar with warmups and warmdowns. Shouldn't the same thing apply to active workers?
Penland Craft School in North Carolina has had a Movement Program for years. They usually have a movement person on staff, a person from a specific discipline, who goes from one craft area to another where he or she can study and correct a craftperson's posture as it relates to the work.
I am wondering about the hammer handle study, however. What is the shape of the wooden hafts in the study? When I purchase a wooden haft, often 2nd growth hickory, it is covered with lacquer and it feels really clubby to my hand, sort of like holding the wrong end of a baseball bat. I always sand and shave it down, and I make the neck on the American style haft quite thin. I make the handle portion fit my hand. I have no studies to prove my point, but I believe the thinned neck not only takes shock properly, but it might even whip in midair on a hefty backswing.
We also get to the subject of objects being termed ergonomic, such as chairs and hammers. For example, "I have an ergonomic hammer."
"Really? Mine is more ergonomic than yours." Whoa! All of this requires study.
I would be curious as to Cole's sources for correct static and force at the anvil. Is this personal conjecture after studying ergonomics?
Stretching and proper movement can help control that tension from hammering. The issue with the wood hammers handle is vibrations here is the link to the study on hammers http://people.seas.h...ers/hammers.pdf. I use some wood handles fiber glass and metal. I my self bought a Stanley hammer with a fiberglass handle and one with a metal handle. Remember the key to good ergonomics is to keep thing changed up no one method is good. different but safe stances different but safe swings. Frank the source is from OSHA applied ergonomic principles in the work place and then personal experiences I would like to here your opinion on the subject.
Before rambling on, I must say that "ergonomics" has become a buzzword, a word that is oft used and not always correctly, especially in advertising and talk shows.
I got a book a few years ago that I thought would answer my questions about stance and movement at the anvil and in the workplace: "Ergonomics and Safety in Hand Tool Design" by Charles A. Cacha, 1999. Well, it was an expensive little booger, and it did not give me much specific help. Turns out that it is written as a college text, probably for students in Occupational Therapy. In terms of an overview however, the book is good because it gets into pathology, physiology, anatomy, anthropometry, kinesiology, and biomechanics...before getting to ergonomics. It has some good drawings.
I have been concerned over the years with getting students to swing and stand properly at the anvil. I was in a 12- week horseshoeing school in 1964, and our instructor looked at me hammering one day and said to the class, "Boys, I want you to watch Turley here. He has the proper hammer swing for drawing metal. Go back to it Turley, so that they can watch." I was flattered but also flabbergasted. The old man hardly ever paid a compliment. I went back to hammering, and the old man approved. That experience is embedded in my peanut brain. I remember my stance and swing from that time, and I've tried to emulate myself BOL. As Cole describes above, I do keep my feet side by side when drawing metal, but they are not shoulder width, maybe half shoulder width. I can't tell you whether that is good or bad. Shoulder width might be better. I'm a student of tai chi since 1981, and it is recommended that we have shoulder width stances a good deal of the time. With shoulder width, your leg/foot bone column is vertically in line with the pelvic girdle. And yes, sometimes one foot is ahead of the other, but it is still shoulder width. As Cole says, one foot can advance or step backwards when smiting iron; it depends on what you're doing. In the tai chi Yang Form, there is a beginning arm raising and lowering which is done in a relaxed manner. It has a feeling of "swimming in air." An attempt is made to not use muscles, but to "let the wrists float forward and upward" to shoulder height. The arms follow. Then the arms withdraw and are lowered to the side. This exercise is nigh a dead ringer for a hammer swing. In martial arts, it is a bridge and a push.
In tai chi and chi kung, we are told to "unlock our joints." This, I feel, is good advice. If you tell a person to bend their knees a little, they usually bend them too much. Unlocking the joints is a different feeling. Let's say that you stand at attention as we do in the service and then lock your joints, you are definitely uncomfortable. Then, tell yourself to unlock all joints. You "let go." Now you're ready for a more relaxed approach to the physical work.
I tell my students that in the U.S., we learn to throw, especially in sports, such as baseball, football, and basketball. In Europe, there is more kicking because of the popularity of soccer. We are rock throwers; who hasn't skipped a rock on water? Well, I tell my struggling students that hammering is akin to throwing. If you're feet are grounded, there is an energetic lash-like bodily movement in the hammer lift and hit.
Edward Martin, recently deceased, was a superb smith from Closeburn, Scotland. I visited him in Closeburn a few years ago, and he produced a gold medal that he received from The Worshipful Company of Blacksmiths in London in the year, 2000. It was about 3" in diameter. It said, "Awarded to Edward Martin, Supreme Master Blacksmith." Mr. Martin said it was the third such medal awarded in the last 100 years. I had met Mr. Martin in the U.S., first at a farriers' conference in Albuquerque, and later at a symposium in Lexington, Kentucky. He said that when he swung the hammer in drawing metal, "There is a wee bit of a draw-back feeling as you contact the iron which may be more apparent than real." Well, that is sort of an airy statement, hard to define, but I watched him work. I believe he was talking about the arc of the swing, so it appears that the hammer is moving toward you upon contact, not absolutely vertical, nor pushing away. Some beginners use sliding, pushing-away blows, mistakenly thinking that they are really moving metal. No way. Hit the iron fair and square.
There is some bending forward when addressing the work. I make an attempt to keep the bending minimal, and I try to bend forward from the sacrum, keeping a straight back. Occasionally, I will catch myself bowing my back, not good, because I'm wearing bifocals and am taking a closer look at the work.
Uri Hofi has a method of shifting the haft in the hand when he is drawing metal, expecially when working the end of a bar. This allows the outside edge of his square faced hammer to make contact with the iron, thereby acting as a fuller. This creates friction heat. If you watch Hofi work, his swing is a good grounded swing, regardless of how the hammer is held.
My personal anvil is now two inches above large knuckle height. It seems more comfortable for me, although I had my anvil at knuckle height for years.
One of my teachers was Ernst Schwarzkopf's book, "Plain and Ornamental Forging." The book has a drawing of a hand holding the hammer handle, and the artist shows a huge thumb wrapped around the handle, NOT on top of the handle. I've tried to follow that example. In taking tennis lessons, we are sometimes told to "shake hands with the racket." Well, the thumb goes around, NOT on top. That "shaking hands" grip is what I encourage.
And now, a quotation from Cacha's book, which may help us to understand the ergonomics concept. Pacha says this definition is a narrow one, because it zeros in on the hand tool aspect, leaving out all the physiology and kinetics (which were covered in previous chapters).
"...a specific definition of ergonomics is the discipline which studies how human beings physically posture themselves in relationship to the many different types of artifacts they have created. The artifacts vary in size and complexity and may include vehicles, buildings, furnishings, equipment, materials, controls, implements, and tools. The ergonomist applies the principles of anatomy, physiology, kinesiology and biomechanics to achieve a major mission: the control of muscuoskeletal disease.
Additional missions include the control of other diseases such as cardiovascular disease, as well as, the goal of providing a comfortable environment which leads to efficiency and fewer errors and mishaps."