 |  | Basic Techiques of Blacksmithing: A Manual for Trainers (Peace Corps, 1982, 102 p.) | ||
 |  | Day 4 | ||
|  | Session: 13. Bellows and forge design | ||
| | Session: 14. Forging an African tang-type axe | ||
| | Session: 15. Case-hardened African field hoe with collar | ||
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Total Time: 50 minutes
Objectives:
* To list and describe design criteria for a forge and
bellows
* To evaluate forge and bellows designs
* To discuss the
feasibility of introducing new forge and bellows designs to local blacksmiths
Resources:
* Attachment 13-A, "The Japanese Style Box Blower"
*
Attachment 13-B, "How to Build a Blacksmith's Blower"
* Attachment 13-C,
"Lorena Forge Design"
* Attachment 13-D, "Forge Pump Designs"
Materials: Newsprint and felt-tip pens
Procedures:
Step 1.
Explain the session objectives and briefly outline
the procedures. -
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Trainer Notes Explain that the design and construction of a bellows and forge will be only briefly discussed during this training since the design of this equipment is extremely relative to and dependent upon the needs, desires and resources of local blacksmiths. |
Step 2.
Have the participants list and describe the design
criteria for a bellows and forge.
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Trainer Notes * Write their responses on posted newsprint according to the example below: Design Criteria Bellows Forge * Assist participants in developing the lists by providing a few examples and asking the following questions: - Do the forges and bellows used here at the training meet the
criteria? If so, how? |
Step 4.
Distribute Attachment 13-A, "The Japanese Style Box
Blower,'' Attachment 13-D, "How to Build a
Blacksmith's Blower," Attachment
13-C, "Lorena Forge Design," Attachment 13-D, "Forgo Pump Designs," and ask
participants to review them.
Step 5.
Have participants discuss the feasibility of
introducing new forge or bellows designs to local blacksmiths.
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Trainer Notes Some questions for discussion include: - Do the designs outlined in the Attachments offer any advantages over traditional types of forges and bellows? How? - Do the new designs meet the criteria developed earlier in the session? - What difficulties might you encounter in attempting to construct one of the new designs at a local blacksmith shop? |
Step 6.
Conclude the session by asking one of the
participants to briefly summarize the major factors which should be considered
in designing a forge and bellows.
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Trainer Notes Caution participants against making recommendations regarding forge or bellows innovations without taking time to thoroughly consider the needs, desires and resources of local blacksmiths. |
Attachment 13-A
The Chinese/Japanese style box blower
This traditional blower has been used in China and Japan for hundreds of years. It may be constructed in varying sizes. It is used in large lever-powered applications for foundries. Medium sizes (12"x18"x30") are used for forges and small versions are used for home cooking fire blowers.
Blowers may be made from almost any kind of scrap planks, if well-sealed around seams and cracks.
The inner slide chamber should be smooth and preferably waxed or varnished.
The two air inlet valves should be made of fairly heavy leather, and the hinge for the air exit flapper valve should be centered carefully. The bevel-cut on the side should align for a good seal.
It is a good idea to leave the top accessible by not sealing it with glue.
Box blower
Attachment 13-B
HOW TO BUILD A BLACKSMITH'S BELLOWS
Allen R. Inversin, Appropriate Tech. Development Unit, Lae, Papua New Guinea
Blacksmith's bellows
BACKGROUND
The idea for this bellows came from the time-tested, valved, teardrop shaped design which has been in use since about the fourth century. However, as leather is not readily available in Papua New Guinea, a slightly modified version was designed using the inner tube of car tires which can be obtained anywhere in the country. The bellows cost very little to build and require no special skills for construction. It provides a continuous blast of air to the forge, which is more than sufficient to fabricate machetes, chisels, chains, hinges, spikes, etc.
MATERIALS
- Two normal-size car tire inner tubes in good condition and one
tube to cut up,
- Four 1-2 cm. boards, each about ½ m. square, of
plywood or narrow boards laminated together.
- Wooden strips around 2x5 cm.,
totalling about 6 m. in length.
- Used steel pipe, 2-3 cm. in diameter,
length 6 m. or more.
- Sheet metal or used steel banding straps.
- Four
metal rods about 5 mm. in diameter and 10 cm. long.
- Nails, about 2 and 4
cm. long.
USE OF THE BELLOWS
Although they are easy to use, the bellows should be stroked in a particular way to prevent the user from becoming unduly tired. Two points should be kept in mind:
- Rather than making quick, short strokes, make smooth, full ones starting with the lower board all the way down, and stroke to compress the lower inner tube almost completely.
- The air reservoir (upper tube) should never be fully extended. If a greater air flow is needed to increase the fire temperature, place weights (pieces of iron, stones, etc.) on the upper board to obtain desired heat. Only stroke fast enough to keep the upper tube partially full at all times. A full stroke every 5-10 seconds should be sufficient; stroking any faster produces more sweat than heat.
Attachment 13-C
LORENA STOVE DESIGN
Lorena stove design
Lorena is a rammed-earth technique that uses a moist combination of screened sand and clay. The sand/ clay mixture is applied in layers and pounded and compacted into molds. The primary advantages of Lorena mix include its low cost, general availability, and good heat-holding capacity. For a complete explanation of the techniques involved in working with Lorena mix, send for a copy of Lorena Stoves, by Ianto Evans and Michael Boutette, from Volunteers in Asia Press, Box 4543, Stanford, California 94305 USA.
Bottom Blast Forge; Side Blast Forge
Attachment 13-D
FORGE PUMP DESIGNS
Fan-type forge pumps
Double-acting piston forge
pump
Total Time: 3 hours, 10 minutes
Objectives:
* To make an African axe
* To build endurance by working
heavy metal in several consecutive heats
Resources: Attachment 14-A, "African Tang-Type Axe"
Materials: One section of leaf spring (car), ¼” thick per station; prototype axe with handle; several branches of wood suitable for handles (see Step 13).
Procedures:
Step 1. (5 minutes)
Briefly explain the objectives and pass a
prototype axe among participants for observation.
Step 2. (10 minutes)
Ask the group to identify the metal
source and components of the axe, and list on newsprint the
steps involved in
its production.
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Trainer Notes * Be sure the following components of the axe are mentioned in the discussion: - cutting edge * Participants, at this point in the training, have 1 earned and used most of the techniques involved in making an axe. As they identify the steps involved, assist only at points where new techniques are being introduced; e.g., forming the tang. Their list should include the following steps: - hot-cut the leaf spring * Mention that in a more industrialized situation, the axe surface would be finished using a flatter, but for training purposes, this is not necessary. |
Step 3. (5 minutes)
Distribute Attachment 14-A, and ask
participants to refer to it as they watch the trainer's demonstrations and
during their forging process.
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Trainer Notes Explain to the group that since axe forging entails considerable labor, only one axe will be made per team. |
Step 4. (10 minutes)
Discuss the leaf spring as a source
metal and demonstrate how to hot cut it.
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Trainer Notes * Ask for a volunteer from the group to test the leaf spring for hardness and discuss its properties. * Have the group discuss the local availability of leaf spring and suggest alternative materials for axe-making. |
Step 5. (15 minutes)
Have the teams go to their stations and
hot-cut their leaf springs.
Step 6. (10 minutes)
Explain and demonstrate the upsetting of
the work-piece and peening of the axe head.
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Trainer Notes Be sure to discuss the following points: * proper techniques for using cross- and straight-peen hammers * use of quick, light blows to keep the heat in the metal, to allow longer workability and to reduce bending. |
Step 7. (30 minutes)
Have the teams upset the blades and
draw-out the tangs on their axe heads.
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Trainer Notes * Circulate among the stations providing assistance when requested. * Pay particular attention to participants' hand hold on hammers, force of blow, quickness and posture. |
Step 8. (10 minutes)
Demonstrate how to finish the axe
surface and forge the wedge tang.
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Trainer Notes While forging the wedge tang, mention the danger of burning the small tang in the forge. |
Step 9. (20 minutes)
Have participants finish and forge the
wedge tang.
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Trainer Notes Assist any teams who appear to be experiencing difficulty. |
Step 10. (15 minutes)
After the teams complete the forging
process, have the participants, as a group, identify problems encountered in
each step and discuss possible solutions.
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Trainer Notes To provide structure to the discussion, chart their responses in the following manner on newsprint: |
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Step |
Problem |
Avoid By |
Correct By |
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upsetting etc. |
Bending, folding etc |
light, quick hammer blows etc. |
corrective, quick straightening etc. |
Step 11. (25 minutes)
Have the teams grind and temper their
axes.
Step 12. (5 minutes)
Briefly discuss the handle of the axe
and demonstrate how to align and mount the axe head.
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Trainer Notes * Have the group identify suitable wood types for making handles and discuss shaping techniques. * Explain the significance of the burl on the end in keeping the handle from splitting and adding weight to the axe. * Mention that axes may be soaked in mud to keep handles from splitting and to keep the axe head secure. |
Step 13 (30 minutes)
Have participants find suitable wood for
handle-making, form the handles, and mount their axe heads.
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Trainer Notes * If appropriate wood types are available in the vicinity, ask the teams to explore the area and find branches from which to form the handles. * If wood is sparse, provide the group with several pieces of raw material from which to choose. |
Attachment 14-A
STEP BY STEP ILLUSTRATION OF AXE-MAKING PROCEDURES
African Tang-Type Axe
1. Material
2. Upsetting
3. Spreading
4. Drawing Out Edge
5. Drawing Out Tang
6. Mounting
Handle
Total Time: 4 hours
Objectives:
* 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
Resources:
* 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.
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Trainer Notes * Preparation for this session will involve: - completing one prototype field hoe (see Step 2) |
Procedures:
Step 1. (5 minutes)
Explain the session objectives and
briefly outline the procedures.
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Trainer Notes 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.
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Trainer Notes 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.
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Trainer Notes * 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.
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Trainer Notes * 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.
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Trainer Notes * 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.
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Trainer Notes * 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.
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Trainer Notes * 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.
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Trainer Notes Provide assistance whenever necessary. |
Step 9. (10 minutes)
Reconvene the group and have them
discuss any technical difficulties which they encountered.
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Trainer Notes 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.
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Trainer Notes * 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. |
Attachment 15-A
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.
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