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Forging a Taper
The process of tapering is one of the five basic processes used in forging steel. While it is virtually impossible to taper a cold piece of steel, it is very common and easily accomplished while the metal is hot and malleable. I will explain two processes used in forging a taper. The first will be explained using the standard cross-peen hammer and anvil. The second will be explained using a mechanical hammer. In fact, there is a QuickTime movie (1,466K) which shows the tapering process on a 25lb. Little Giant mechanical hammer. This clip will give you a good idea of working the end of the bar to achieve the taper.
The first process will be done on the anvil using a cross-peen hammer. This process can be broken down into two parts. The first (#1 above) process is to rough out the basic form over the anvil horn. Remember to get the metal hot enough. It should be bright yellow in color, almost at the burning state. That way you will get the most out of the heat.
Place your piece over the horn and use the cross-peen section of your hammer. By using the smaller diameter of the cross-peen, you will move the cross sections of metal quicker. Also note that by placing the piece over the horn, you will also extrude, or push the metal outwards. Note that both striking surfaces have a narrower diameter than if you were to use the flat of the hammer and anvil face.
You should also learn to control your hammer blows. When you first start out forging your taper, you should consider working the metal into a square section. This should be done even if you start out with a round bar and you want to end up with a round taper. By maintaining a square cross section, you can see the taper develop better than if you were to randomly strike the different surfaces.
After roughing out the taper on the anvil horn, you will probably want to get another high yellow heat before refining the taper. Remember that it is easier to reheat than to try to finish the taper after it has lost its color. Knowing when to stop will come with practice. When the metal gets to the dull red state and you know you still have to do additional tapering, you should stop and put it back in the fire.
The second (#2 above) and final heat will be done on the anvil face using the face of the hammer. You will want to continue working the piece with a square cross section until you have achieved the desired taper. Note that when you get close to the tip of the taper, you will want to hammer it near the edge of the anvil. Not doing so, will likely damage your anvil and hammer. You will also notice that it will be very difficult to strike the very tip of the work unless it is near the edge.
Now, if you are planing on making a round taper, you should work the piece on each of the four edges. This will then make the taper into an octagon. Further working of the eight edges will eventually give you a round taper.
So much for hand tapering over the anvil. If you are planning to do lots of tapering, and believe me, much of the processes of forging steel incorporates this process, you may want to use a mechanical hammer. The trip hammer, which is similar to the mechanical hammer, dates back to the era of water wheels. The first trip hammers were used in conjunction with water power. The force of water in conjunction with mechanical gears allowed the blacksmith to make a machine that would lift a large hammer head and then drop the head over an anvil base. Thus allowing the blacksmith to work larger pieces of metal with little manpower.
This method of working metal was later redesigned to use electric motors instead of water power. The concepts remained the same but allowed for mechanical hammers to be placed anywhere there was electric power. Today, the typical mechanical hammer has again been replaced with pneumatic and hydraulic hammers. We are not going to go into the differences between the different types of mechanical hammers. Just realize that what you have done on the anvil with the hand hammer is accomplished also on a mechanical hammer. The only difference is that with these mechanical tools, you are able to work quicker and more effectively. You will also note that when you start working larger diameter material, you will come to a point that you wished you had some type of mechanical hammer to help you do the work.
The only point that I would like to make about mechanical hammers is that the piece is pushed, pulled, and turned on the hammer die and control over the amount of force is controlled by a foot treadle. The harder you step on the treadle, the more force is directed to the hammer head.
I hope that this article has given you an idea of the forces required to shape metal. It is only one of the many different types of processes used by the metalsmith to bring form to their creations.
Copyright 1995 Enrique Vega / ArtMetal
ArtMetal Author / Curator: enrique