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Teacher
Edition Contents
Skill,
Tools, & Craftsmanship
Cutting
& Drying Fish
Sharpening
Nails,
Pegs, & Lashings
Falling
Trees &
Small-Scale
Logging
Guns
Chainsaw
Clutch & Chain
Ice
Pick
Shelters
Wood
Stoves
Wall
Tents
Steambaths
Insulation
& Vapor Barriers
Gas
Lamps & Gas Stoves
Travel
Piloting
A Boat
Boat
Design
Magnetos
& Spark Plugs
Carburetors
Compression
Outboard
Motor Lower Unit
Outboard
Motor Cooling System
Dogsleds
Snowmachine
Tracks
Snowmachine
Clutch
Snowshoes
Winter
Trails
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Activities
Note: In the following activities you are asked to use tools and
blades. There is obvious danger. Be careful!
- Collect as many blades as you can. Identify tools for cutting
wood, dirt, metal and food. Are they sharpened on one side or
both? Look at the above edges with a strong magnifying glass.
Draw several of them.
Answers will vary.
- How thick are the edges? Can you find a relationship between
the materials they cut and the thickness?
Materials that cut dirt and metal will have a thicker edge
than those that cut wood and meat.
- Try to sharpen all of the above tools with a file. Are some
of the edges harder than others? What do people use to shape and
sharpen the harder steel tools?
Some steel is quite hard, like the carbide blade tip on a drill
that drills concrete. Steel that cannot be filed can often be
sharpened with a stone, but some metals are too hard for stones,
and must be sharpened commercially.
- Carefully test the blade of a hand plane with a file. Are both
sides equally hard?
No the cutting edge is much harder than the back side.
- Tap the above blades with a piece of hard steel. Do any of
them ring? (Small blades are hard to test.) What can you say about
the steel that rings?
Steel that rings is high carbon steel, and makes a good edge,
although it isn’t necessarily hard.
- Carefully test a dull knife in cutting wood. Bring that same
knife to someone who knows how to sharpen. Ask that person to
sharpen the knife for you. Try it again. Is the difference noticeable?
Like night and day.
- Try cutting wood with a steak knife. What happens and why?
Very difficult. The serrations on the steak knife are too rough
to penetrate the wood.
- Try shaving a piece of wood with a razor designed for a man’s
face. Use gloves. What happens and why?
The razor breaks because it is too thin.
- Try digging with a dull shovel, particularly in a place with
grass or small roots. Sharpen the shovel. Do you notice any difference?
Night and day.
- Look at a dull edge under a magnifying glass. How is it different
from what you expected? Can you understand why pushing such a
rough surface into your work is difficult? Now look at a sharp
edge with the glass. Even this looks crude. Compare both blades
in ten words or less.
It is thick and quite rough. The sharp edge is much thinner,
although the marks from the file or stone are obvious. It’s
a different world down there.
- Scissors don’t cut the same way as a knife. Study scissors
and describe how they cut.
Scissors cut by shearing the material. They don’t penetrate
like a knife. They tear one half of the material from the other.
- Cut fish with a dull knife. Sharpen it and cut fish again.
Estimate what percent of effort was saved by sharpening it.
Night and day.
- Sharpen the chain and cut the same block, again timing the
cut. What is the difference?
A sharp saw could be two or three times faster. But time isn’t
the only consideration. Wear on the saw, bar, chain and operator
are greatly reduced by a sharp saw.
- Ask in the village if anyone knows how to sharpen a Swede saw.
Ask the person for instructions.
There might be someone left who knows how. Inquire in other
villages.
- Collect different files. What are the differences other than
size? Put a piece of paper over the file and with a crayon or
lead pencil do a “rubbing” of the file. Compare the
imprints from the different files.
There are many kinds of files. Some are rough. Some are smooth.
Some are double and some are single cut.
- With an old file, file aluminum (like an old prop). What problem
arises?
Aluminum is soft and files easily, but the aluminum plugs the
file.
- Compare the two sides of a sharpening stone. Which one is for
faster and which one for finer sharpening?
The difference is obvious. One side is rough and the other
smooth. The main thing is to keep the file clean of dirt that
plugs the pores and glazes the surface so it can’t cut anything.
- Sharpen a knife for meat and finish the edge with a butcher’s
steel. Cut a little meat. Now try the same edge on wood. What
do you notice? Strop the edge back and forth on a piece of leather
for a while and then try again on both meat and wood. What do
you notice? Which edge is better for meat, the rough or smooth
one? Which is better for wood?
The knife that is sharpened with the butcher steel will cut meat
well, but will be too rough for wood. The edge that is stropped
will be good for wood, but not quite as good on meat. Rough is
better for meat, smooth better for wood.
- Students should each share a story of a time they cut themselves
being careless with a tool.
- Draw or trace a Swede saw blade identifying the two kinds of
teeth. Describe to someone else how each of these relates to a
modern chainsaw tooth.
The V shaped teeth are like the side plate of the chainsaw tooth.
The other teeth are like the top plate.
- Picture in your mind what would happen if a Swede saw blade
had only this kind of teeth.
- Picture what would happen if it had only this kind of teeth.
- If you can get some beaver or muskrat teeth, test the front
and back for hardness. Explain how they are self-sharpening.
The front of the tooth is very hard. The back of the tooth
is softer. The back wears faster than the front, therefore leaving
the thin hard edge. As they are used they are self-sharpening.
- Picture in your mind what is happening when the rakers on a
chainsaw chain aren’t filed evenly. Can you imagine the jerking
of the chain as some teeth bite deeper into the wood than others?
- Put pressure on a bathroom scale with a fish cutting knife.
Record how many pounds you can assert. Now put pressure with an
ulu. How many times more pressure is possible with the ulu? Test
the whole class. First let students estimate the test. How many
times more pressure can the ulu put than the knife? Average the
results. How does the knife serve as a lever?
The ulu can usually put 4–5 times more pressure than the
knife. If you think of the knife as a lever and your thumb on
top as the fulcrum, you will see that the fish actually has a
mechanical advantage over your hand.
Student Response
- What happens when an edge is too thick?
It pushes the work away rather than penetrating the material
- What happens when an edge is too thin?
It cuts well, but breaks easily
- What are the three considerations in sharpening a tool?
At what angle is the edge formed?
How thick or thin is the actual edge?
How rough or smooth is the edge and sides of the blade?
- What two things determine how thick or thin an edge can be?
Hardness of the steel and the material being cut
- Draw a shovel blade sharpened for rocky ground. Draw one sharpened
for ground with no rocks, but lots of roots.
The one for rocky soil will be thicker
- What is the difference between cutting meat and wood in terms
of the friction of the blade?
A blade for cutting meat has a rougher edge. A blade for cutting
wood has a smoother edge to reduce friction
- Draw a Swede saw blade. Which teeth are for cutting fibers
and which for chiseling the severed fibers out of the cut?
- Which is harder: a file or a sharpening *stone?
A stone
- An axe of fairly soft steel has a hard spot. What might cause
this?
Someone hit a rock with the axe and hardened the steel at that
point.
- Why do people put oil or saliva on a sharpening stone?
To float the particles out of the stone so it does not plug
and glaze over.
- Why do we put pressure only on the forward stroke of a file?
The teeth are strong when filing in a forward direction. If
pressure is put on the file during the backstroke, it will fold
the teeth over and damage them.
- Draw a chainsaw tooth. Label which part severs fibers. Which
part chisels the fibers from the cut?
- What do the rakers do on a chainsaw tooth? What happens if
they are too high? Too low?
The rakers determine how much each tooth bites into the wood.
If they are too high, the teeth can’t bite enough. If they
are too low, each tooth will bite too much.
- Why should the height of the rakers be the same on all teeth?
If they are irregular, they will bite unevenly, jerking and
stressing the chain. Uneven rakers will also cause the saw to
kick back.
Math
- When Sal cuts fish she puts about 15 lbs pressure on her knife.
She finds that sharpening reduces the surface area of her cutting
edge by 30%. How much pressure will she apply to do the same work?
10.5
- Hank can cut a block of wood in 30 seconds when his chainsaw
is sharp. It takes 1.5 minutes when it is dull. If he can cut
a tree into blocks in 25 minutes with a sharp saw, how long will
it take with a dull saw?
75 minutes (1 hour, fifteen minutes)
- Hank also discovered that he could increase the speed of ripping
by 35% by filing the rakers on his saw from .025 to .040. If he
could cut 350 board feet before, how much lumber can he cut with
the rakers filed properly?
472.5 board feet
- Hank estimated that it would take him 5 days to cut the lumber
he needed. Once he filed the rakers, he cut 35% faster than expected.
How long will it take him to cut the lumber now? [(x v .35x) z
5]
x = 3.7 days. Not 5-(.35 x 5) = 3.25
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