|Basic Techiques of Blacksmithing: A Manual for Trainers (Peace Corps, 1982, 102 p.)|
Total Time: 4 hours
* To forge a field hoe with collar
* To discuss case hardening as an alternative to tempering
* To case harden a field hoe
* To examine difficulties encountered by local blacksmiths in making agricultural tools
* Attachment 15-A, "African Field Hoe"
* Andrews, pages 119-122.
Materials: One completed field hoe, one piece of field hoe material ready for swaging, one field hoe ready for case hardening, carburizing agent, approximately 20 square feet of 1/8" mild steel.
* Preparation for this session will involve:
- completing one prototype field hoe (see Step 2)
Step 1. (5 minutes)
Explain the session objectives and briefly outline the procedures.
Explain that there are many different designs of field hoes which vary greatly from country to country. The design used in this session is meant to provide participants with the basic steps involved in making a hoe and may not necessarily be appropriate to their work sites.
Step 2. (10 minutes)
Distribute Attachment 15-A, "African Field Hoe." Pass around a sample field hoe and ask that participants examine it carefully and think about the procedures involved in forging it.
Point out that the procedures illustrated in the attachment can serve as a guide.
Step 3. (15 minutes)
Ask participants to describe the steps involved in making the hoe, and point out any new techniques which they have not yet seen demonstrated.
* Explain that they have already practiced most of the techniques necessary to make the hoe.
* Some of the techniques with which the participants will be experimenting are:
- cutting the stock to proper size (10"x5")
* During the discussion, it can be assumed that participants will identify the swaging of the workpieces as a new technique which they have not yet practiced.
Step 4. (10 minutes) Briefly explain and demonstrate the process of swaging.
* For the demonstration, use a workpiece which has been pre-cut and taken to the point of swaging the collar.
* Be sure to point out and explain proper use of swages and fullers and several applications of the processes.
Step 5. (2 hours)
Have the participants form their work teams and make a field hoe up to the point of case hardening.
* Circulate among the work teams and provide assistance whenever necessary. Be careful to allow participants the maximum opportunity to work among themselves and creatively seek ways of overcoming difficulties they may be experiencing.
Step 6. (10 minutes)
Reconvene the group and have participants discuss case hardening as a viable alternative to tempering for local blacksmiths.
* Ask participants to identify some of the factors which make it difficult for local blacksmiths to temper steel. Mention such factors as the unavailability of temperable steel stock (other than leaf springs) and the time and heat required to draw out leaf springs.
* Explain that their hoes are made of 1/8" mild steel which cannot be tempered. The hoes can, however, be hardened by putting a hard coat or "case" on the outside of the steel. This process is called "case hardening."
* Briefly describe the process of the molecular migration of carbon into steel.
* Ask the participants to describe how case hardening can be a desirable alternative to tempering.
Step 7. (15 minutes)
Demonstrate the proper procedures and techniques for case hardening a field hoe.
* Include in the demonstration such techniques as:
- proper use, mixture, and placement of carburizing agents
* Briefly describe alternative carburizing agents (wood, charcoal, animal bone, leather, etc.) and mention other methods of case hardening.
Step 8. (35 minutes)
Have the participants return to their stations and case harden their hoes.
Provide assistance whenever necessary.
Step 9. (10 minutes)
Reconvene the group and have them discuss any technical difficulties which they encountered.
Stimulate discussion and a sharing of experiences by asking:
* Which techniques seemed easy to perform? Why?
* Which seemed difficult? Why?
Step 10. (10 minutes)
Conclude by asking participants to discuss the difficulties encountered by a local blacksmith in making agricultural tools.
* The following questions can serve as a guide in focusing the discussion:
- What problems did you encounter in attempting to make the hoe
based on the instructions given?
* Mention that in the next session, participants will be asked to make a cross-peen hammer based on a set of instructions and that they should bear in wind the key points of this discussion during that activity.
AFRICAN FIELD HOE
Select and cut materials
SELECT AND CUT MATERIALS
Lightweight, durable field hoes can be forged from heavy gauge sheet metal. Car bodies, truck panels, and some tank containers (water heaters, propane tanks) are potential sources of this type of metal.
To make an all-purpose field hoe, begin by cutting a piece of 1/16" mild steel (sheet metal or other) into a rectangle 10" x 5". If the metal is not flat, flatten it.
FULLER THE STOCK (optional)
When leaf spring or other heavy metal is used, the stock must be fullered. Bring the stock to forging heat and notch it at the point where the blade material separates from the collar (socket) material.
In order to make the notches, use a set of top and bottom fullers. The set may consist of:
1) handled top fuller, anvil-held bottom fuller (hardy)
2) two cast iron or steel pipes (the bottom pipe can rest on the ground or be held in a vice)
3) swage-block bottom fuller (turn the swage block on its side and use the built-in fuller), handheld top fuller (pipe or handled)
Cut the blade corners; spread the blade, taper the blade; round the blade
CUT THE BLADE CORNERS
Heat the end of the blade and cut off the corners. This will make it easy to give the blade a rounded nose later (Step 5).
SPREAD THE BLADE, TAPER THE BLADE
Bring the blade to forging heat and begin to draw the nose into a taper. Direct hammer blows so that the metal spreads and forms a curved blade, and the blade thickness graduates from 1/16" to 1/32" from back to front.
ROUND THE BLADE
Heat the blade and bring the edge to finished roundness. Hold the blade at right angles to the anvil and hammer the uppermost edge; if the metal has been uniformly heated, both top and bottom edges will be worked with each hammer stroke. (The action of the hammer strike will be equal to a reactive "strike" by the anvil.)
Sink the blade; form the collar
SINK THE BLADE
Bring the blade to forging heat and lay it ever a mold having the desired curve. Use a wide ball-peen hammer to "sink" the blade into the mold. The mold can be pre-made by pounding a finished blade into hard earth.
An alternative method for bending the blade is to hammer it over a form (anvil, car bumper, earthen mound, etc.)
FORM THE COLLAR (socket)
Form. the collar by heating the socket material and hammering it around the horn of the anvil (7A). Finish it by closing it around a bick horn or other tapered object similar to a hoe handle (7B).
Select a handle; mount the handle
SELECT A HANDLE
Choose a hardwood with the desired thickness and shape and hew it into a handle. Tree forks make excellent handles because they have tight, twisted grain. Taper the shaft so it slides into the collar.
MOUNT THE HANDLE
Place the shaft into the collar. Set it by tapping the heel of the handle on a rock or log.
The blade can be taken off the handle by tapping the shaft against any hard surface.