Original subtitles

- [Narrator] Table, circular, chain or jig,

it's one of the most essential tools in the world.

A truly cutting edge technology

worth over billions of dollars.

- We've a lot of mills

all over the United States.

- [Narrator] From humble, prehistoric origins,

through medical discoveries and industrial revolutions.

This tool's ability to both create and destroy.

Have made it a cornerstone of human achievement.

Better stay sharp because you'll never hack through wood

the same way again.

With saws on Modern Marvels.

[saw blade purring]

[upbeat music]

[metal clinking] [water bubbling]

[saw machine purring]

It's an 800 pound behemoth

and it's loose in the Washington state forest.

Spinning at a blinding 200 miles per hour.

It's taking down everything in its path.

[saw blade purring]

It's the circular saw blade on the John Deere 959J

and it means business.

This blade, which at close range

sounds more like a jet engine than a saw.

Takes one second to blow through an 18 inch diameter tree.

It's carbide teeth are bolted to a huge circular blade.

That dishes out punishment for up to 10,000 hours.

Cutting down as many as 2 million trees

before workers have to swap it out.

- It's a hardened steel blade

that is balanced during the manufacturing process,

much like the flywheel on an engine or the tires on your car

so that it spins freely and spins and balanced.

- [Narrator] The Circular Saw is recognized

as the most useful, popular and versatile

of all the power saws.

Spinning at 1200 RPM, this huge saw blade

severs a tree completely before the grab arms grabs them.

- If you actually clamp onto a tree and cut it,

you can induce some stress into the tree

and actually cause some damage to the tree.

And as a result, you're never clamping onto the tree

until after it's cut.

- As soon as you see the first chip flying,

you have to be closing your grab arms

instantly otherwise you are dropping trees

where you don't want them.

- [Narrator] Forest harvesting

the process of cutting and clearing a forest

employs the use of various heavy duty machinery.

The 959J rig is one of these massive machines,

commonly called a Feller Buncher.

And a Feller is someone who cuts down these trees.

The Feller Buncher is used to cut and gather

several trees at once.

The Feller Buncher specs; 90,000 pounds, 294 horsepower,

hydraulics that tilt the cab and an 8,700 pound cutting head

that rotates 310 degrees.

Its power is used to service one thing.

Finding a way to level that blade

into fresh wood cleanly every time.

A skilled Feller Buncher operator

like Dale Stoken is a multitasker.

Maneuvering and stabilizing his machine

on steeps slippery grounds as he chops down trees.

Threads them through the canopies obstacle course

and piles them like so many matchsticks.

With this $600,000 Feller Buncher,

Dale can cut down anywhere from a 100 to 200 trees an hour.

But how do you stay safe while you're harvesting trees

as tall as a 20 story building.

- These polycarbonate windows are literally bulletproof.

And so they're meant to withstand the impact from debris

and trees that that may come down out here in the woods.

- Well, I haven't had any trees fall on this machine yet

tops, rotten pieces, snakes, a lot of dead wood

in the stand of timber.

They bang on it, but it's built pretty heavy duty.

- [Narrator] Ultimately the key to Dale's safety

is knowing his limits.

- A lot of times we have timber

that's too big for the Buncher, can't handle it.

And the steeper ground like, on the backside here,

he's not gonna be able to get in here with that machine.

He slides around too much.

- Dale leaves the job to the crew on foot

to cut down the trees

with an entirely different kind of saw.

A steel MS 460 chainsaw.

This chainsaw's motor engages a Sprocket

that drives the cutting chain.

The saw chain is comprised

of alternating left and right cutters.

Each tooth is capable of cleanly slicing off a chip.

But if the cut is incomplete,

the opposing cutter will finish the job.

Severed chips are carried away through the chip channel

to be ejected at the end of the cut.

[saw blade purring]

With chainsaw in hand, a skilled logger,

will take down a tree like this Western hemlock

in about 30 seconds.

- You start as what's called, your top cut

and you start your saw here.

When you're finished with your top cut,

you get behind your saw

and you look down the site of your saw

out there, 50 to 60 feet

and sight in on something out there.

And that will determine where your tree's gonna lay.

Then as your slope cut,

you can come up underneath and you gotta match up

your slope cut with your top cut perfectly.

- [Narrator] The last cut, the back cut,

actually fells the tree.

- You want to be an inch to two inches

above your original undercut.

And with an even hinge wood.

Hinge wood is what's considered the wood that's left,

which actually steers the tree in the direction

you're falling in.

If you're falling this tree this way

and it brushes another tree or an object out there,

the force of that tree springing can spring back

and actually push that tree back on the stump.

I've seen him come back, 20 to 30 feet back up

through the timber before.

If it hits something, it'll come up against that step

that you're gonna have back here.

And that step of wood will hold that tree upon the stump.

- [Narrator] Everything about this job

from falling timber to the saws is dangerous.

- We had a guy get hurt a few years ago.

He didn't get cut with the saw,

but he got smashed by a top came out of a tree

and smashed him and broke his back.

- [Narrator] With all the sound and furry of power saws,

it's easy to miss some of the subtleties

of what makes a saw a saw.

For that it helps to take a look at a simpler saw.

The panel saw, also known as a hand saw.

Of course the defining feature of a saw is its teeth.

- It's got separately formed teeth

that cut into the material and sliced the fibers away

so that it cuts very, very quickly through the material.

- [Narrator] Saw teeth are only sharp on the forward edge,

the cutting edge.

They're also raked, inclined in the direction of the cut.

- On all western hand saws,

the teeth all basically point

in the same direction, forward.

That's because these saws

are de designed to cut on the push stroke.

And when you pull the blade back, the saws isn't cutting.

- [Narrator] And for every tooth, there is a gullet.

- The gullets are the spaces between the teeth

and these spaces are allowed to fill up

with the material that's being cut away.

It's called swarf.

The swarf builds up in these little gullet.

And then soon as the blade exits at the bottom of the board,

the swarf just falls out of the Gus and falls away.

- [Narrator] The last key feature is the kerf.

The width of any saw cut is known as the kerf

and it's worth knowing this measurement

to get the most accurate cut.

- The actual cutting edge creates a wider kerf

than the thickness of the blade.

So the blade has clearance and doesn't stick in the kerf.

- [Narrator] Despite all these design features,

there's still plenty of skill involved

in making a clean cut with a hand saw.

[gentle upbeat music]

- Now the whole trick to getting a nice clean cut

is starting off with a nick on the edge.

But I'm gonna use my thumb

to keep the saw from moving sideways.

And I'm just gonna pull backwards a little bit

to create a starting groove for the saw blade.

Now I'm gonna bring the angle, my saw to about 45 degrees.

[handsaw chittering]

I'm gonna start sawing.

I lift the saw slightly as I go on the reverse stroke,

so the teeth aren't dragging,

keep sawing until I get right near the end.

I gonna get this close.

What I'm gonna do is I'm gonna hold this piece.

I'm gonna slow down.

I'm gonna saw very gently at the very end

to avoid tearing out the corner.

There's my cut.

- [Narrator] But not all saws has cut on the push stroke.

- Japanese saws, all cut on the pull stroke.

Japanese saws are very, very thin.

When you have a thinner saw,

that means you have to remove less wood to make the cut

so they faster.

- [Narrator] Western saws have thicker blades,

so they won't buckle on the more powerful push stroke.

Japanese pulls saw are designed to cut softer woods.

- The reason we wanna work this low,

we want to be able to use our foot

to hold the work piece down

and then use both our arms on the saw

to get lots of power to the cut.

Now, at the end of the cut,

I slow down a little tiny bit, that comes right off.

[handsaw chittering]

- [Narrator] East or west, modern saws are efficient.

But they're most ancient ancestors,

prehistoric flint saws, Circa 8,000 BC.

Were thick and jammed in the cutting groove.

Around 4,900 BC, Egyptians and Mesopotamians

fashion the first metal saw

with relatively soft metals, like copper.

- And naturally they could only cut very, very soft woods.

Then we basically progress to a point

where we use harder and harder materials.

Bronze and bronze alloys that have the ability

to hold a little bit of a better edge,

right up until we get to iron.

And of course, iron is where we make a major leap

into tools that were really capable

of doing some pretty serious work,

felling trees and cutting up very thick logs.

- [Narrator] The saw of the Iron Age,

roughly 700 BC to 50 AD.

Incorporated two breakthroughs;

teeth that were raked in the direction of the cut

likely in Egyptian innovation

and from the Romans, set teeth bend to the left and right

that created a kerf.

The 19th Century brought widespread use of steel.

Giant crosscut saws soon replaced axes

for the job of cutting down the old growth forests.

[tree thuds]

Ah saws, they're used to cut down trees

and to slice and chop wood.

The modern chain saw packs the power,

but is still popular choice today.

It's lighter and more flexible and commonly called,

the saw that sings.

Is a crosscut saw.

They become much scarcer than they were in 1939.

With their large teeth designed to cut in both directions,

These saws are still considered

the most efficient cutting tool in the forest.

- It's called a misery whip.

They nicknamed that because listening to it,

whip back and forth through the trees

and pulling it like a whip.

And by the end of the day, it was miserable.

So they would take an axe, chopping undercut

in the front of the tree,

whichever direction they wanted it to go.

And then they would start with the crosscut saw.

If you had a tree that was 15 feet in reality,

you had to have a 20 foot or larger Misery whip saw.

You were pulling a lot of steel through there.

- Just hold that.

- Lot of work. [Calvin laughs]

Now that ain't bad.

Just a lot of pulling.

- You ready Hoss? - Yeah.

- Timber!

- [Calvin] This saw right here

is the reason they always said

would never be able to cut it all.

You never would to what this saw.

[Calvin laughing]

- [Narrator] Luckily for loggers,

if not for the forest environment,

the two man crosscut saws day has passed.

But for timber sports competitors like David Moses

and his wife, Annette from Snoqualmie Washington,

this old school saw presents an opportunity

for them to show their skills.

David's father trains them.

- Timer's ready, contestants ready!

One, two, go!

[saw blade chittering]

- This is a modified peg and raker.

And the way these cutters are,

they'll make two cuts on either side

of the wood, which will make a line.

And then this ranker come through and push underneath that

and it'll pull out a noodle.

And the longer the noodle, generally the faster the cut is.

- [Narrator] But these teeth that make the saw sharp

also make it dangerous.

Annette had a painful reminder of this

while competing in July, 2006.

- We were coming back.

We were coming off towards the bottom

and we went right across my knee.

And somehow it moved, just came right across,

ended up with 22 stitches.

- [Narrator] But it wasn't the end of Annette's competitive.

- In fact, we kept going and then when we were done,

I went to the hospital.

Came back and single bucked.

We're a different breed.

- [Narrator] And this chainsaw is also a breed apart.

Few saws are as fast and as dangerous as David's hot saw.

A stock chain saw that has been modified for maximum power.

- This is a hot saw.

And it's a Rotax hot saw,

which is half a snowmobile,

twin cylinder snowmobile engine.

- [Narrator] You heard right?

He said snowmobile.

This $5,000, 35 horsepower hot saw, runs on racing fuel.

Has a motorcycle exhaust pipe,

weighs in at 50 pounds and feels

nothing like a stock chain saw

that would've just 1/6 the power.

- There's just a tremendous amount of force.

So it takes some getting used to.

So the first year I was a little bit scared of it.

You don't wanna stand at the front end of the saw

because there's possibilities of any of the teeth

breaking off and shooting out at the end,

which can come off like a bullet.

- [Narrator] In action, the saw lives up

to its powerful billing.

Do not try this at home.

- Timer's ready!

Contestants ready!

One, two go!

[power saw revving]

- 8.53 that's with three cuts.

So that's with his practice chain, not bad.

The modern lumber mill.

Its basic components haven't changed in a hundred years,

but the heart and soul of the mill,

the saws are thinner, sharper, stronger and faster.

Dahlstrom Lumber Mill in Hoquiam Washington

is a big log mill.

It handles, well, big logs.

- Generally that means a log,

maybe over 20 inches on the small end.

We can run up to five foot from the log through our mill.

- [Narrator] As these large Western hemlocks

roll into the mill.

The first saw they face is a deck saw.

- The deck saw we have here is a chainsaw.

Basically like every chain saw.

This one has a bigger teeth on it.

It's got an eight foot bar on it.

It's capable of cutting logs up to over five feet.

- [Narrator] The chainsaw bucks the logs

or in layman's terms, cuts them to length.

Then the operator runs them through the debarker,

which preps them for the head rig.

A steel bandsaw that does most of the job

of sawing logs into lumber.

- And the band is actually 35 feet in length.

The rim speed or the speed of the blade

is about 8,800 feet a minute or a hundred miles an hour.

- [Narrator] This large bandsaw turning on

six foot diameter wheels is the workhorse of the mill.

It's large enough to cut the big logs.

It's more energy efficient than a circular saw.

And it slices a thinner curve than a circular saw.

Cutting back on wood waste.

As the log approaches,

the head Sawyer attempts to slice the most high grade

or appearance grade lumber out of the outside of the log.

A laser helps the Sawyer to place the bandsaw.

The cants sliced boards that have not been edged

rule down the conveyor belt towards the edger.

- Every saw in the edger is identified

on that table with a laser light.

So the operator knows if he sends that piece of wood

in there exactly where it would be cut.

- [Narrator] A 250 horsepower motor

drives a bank of six circular saws, spinning at 1,750 RPM.

The blades are expensive and require constant maintenance.

- Friction builds heat

and heat is like the enemy of the saw blades or steel.

It warps and distorts it.

So you gotta keep your saw blades cool.

Our band mills and our edge are water cooled.

As you saw, waters is sprayed on the blades

to help keep it cool.

- [Narrator] In addition, carbide cutting teeth,

which are wider than the plate,

curve out kerf for the saw is spin.

Friction is also the enemy of the bandsaw.

- When you get a bandsaw hot,

it can possibly leave the wheel.

It distorts it so bad and it can walk off the wheel.

[upbeat music]

- [Narrator] To maintain the bandsaws,

a saw pier sharpens and widens the teeth,

so that they'll cut a broad enough cut

for the blade to run cleaning.

- This is called wedging.

It's how we make the saw teeth wider

than the plate of the saw.

This turns and it forces the metal up

to the point of the tooth,

which makes it spread out and wider than the plate.

And then we shape it back and then grind it sharp.

And it's ready to go.

- [Narrator] With the help of their dog, Marius

John and Laurel Robarge run the blade maintenance shop

at Dahlstrom lumber.

As they sharpen the blades over several months,

they will grind the width of each blade down

by a couple of inches.

This process extends the life of the blades,

but eventually makes them too narrow to use.

Heat also causes blades to warp.

- You'll get these hot spots and it'll expand.

And then your saw starts wobbling in there.

[metal clinking]

And then we get 'em after that

and you just sit and you bench 'em until the lumps are out

and the teeth are sharp.

Benching is basically what I'm doing on this anvil.

Making sure that if you got high spots

that you gotta pound them back down.

- [Narrator] As the lumber leaves the mill,

it's on its way to becoming an essential part

of some kind of structure.

But one day that structure may face remodeling.

When that time comes an entirely different saw

the Milwaukee Sawzall will be there.

The Sawzall is a reciprocating saw.

A power saw with a blade

that moves back and forth during cutting.

The Sawzall aim is to live up to its name.

- What can't you use Sawzall for,

from cutting birthday cake, to lumber,

to demolition, to fire and rescue to...

I even knew a guy he talked about,

he wanted to get rid of a stump.

So he actually used it to cut down in the ground

to cut the roots of the stump so he could pull it out.

- [Narrator] The Super Sawzall

is the top of the Milwaukee line.

And includes orbital cutting action.

- Normally a reciprocating action

is straight back and forth.

Orbital cutting is more of a circular cut,

it's a much more aggressive cut.

Now have a unique feature to Milwaukee.

It's a 360 degree rotating handle.

This is nice 'cause it allows the contractor

to adjust the handle to the most comfortable position.

Generates zero to 3000 strokes per minute.

So it's literally the fastest

reciprocating saw on the market.

- [Narrator] The Sawzall has no problem

cutting through wood screws and nails.

Even the steel hinges on this door.

- The Sawzall was introduced in 1951

and originally developed for plumbers and electricians.

And actually what they were looking for

was compact, durable, lightweight solution

to cut basically anything that they ran into.

- [Narrator] The original Sawzall

was a heavy all metal tool.

Today's version, incorporates plastics and nylons

for lighter weight and vibration dampening.

This Super Sawzall in its blades

are made at a Milwaukee Electric Tool Plant.

Which is not in Milwaukee.

- And Greenwood, Mississippi,

the heart of the Mississippi Delta, catfish and cotton.

The building itself is 150,000 square feet.

It may send a thousand Sawzall a year.

- [Narrator] The key to making a machine

that's always just about anything,

is manufacturing blades for all types of materials.

- The blade we're looking at now is for metal cutting.

And the reason we know that, because the teeth are finer.

There's more TPI or Teeth Per Inch.

Because you don't wanna have

it's aggressive bite when you're cutting metal.

Comparing it to wood, you can take a heavier cut,

a larger chip because the wood is softer.

Then on metal you have to have a finer tooth.

As you see on this blade,

the tooth is much different from the previous one.

It's much larger.

The angles are different.

The depth of the gullet is different.

And this one is designed for a very aggressive

sheetrock and plaster cutting.

- [Narrator] There were no saws

involved in the manufacture of saw blades.

The teeth are ground in.

- The blade process begins with the uncoiler

with a coil of steel.

The encoiler, encoils it into the straightener.

The blade material is straightened

prior to going into the press.

Once it gets into the press,

the blades are stamped out to the configuration

of the blade itself.

Once they are loaded off of the press,

the blades are accumulated into handfuls sort of robots.

The robot swings over,

picks it up and loads into the grinder.

- [Narrator] A ceramic grinding wheel

grinds the saws tooth pattern into a pack of 90 blades.

The grinding wheel forms and sharpens the teeth

as a mixture of water and lubricant

washes metal filings away.

Workers then load the blades into furnaces

to temper the metal in order to retain its hardness

and its flexibility.

The National Cathedral,

the Empire State Building, the Pentagon.

They all have one thing in common, Indiana limestone.

- What's unique about Indiana limestone

is its ability to be worked.

It's a soft stone relative to limestone.

It's very consistent in color.

For that reason it's been chosen as a building stone.

- [Narrator] The stone projects, an aura of permanence

stateless, calm.

But today the process of cutting it into blocks

is anything but calm.

[machine trilling]

At the quarry, the first cut is the deepest.

In this case, 15 feet down into the limestone bed.

The saw for the job, a WF Meyers, Diamond Belt Saw.

Though designed specifically

for the task of quarrying stone,

it resembles another popular saw.

[power saw machine revving]

- Just picture a chainsaw for example.

And we put a belt around a bar

that is in geometry very similar to handheld chainsaw.

Instead of using a chain,

we use a belt that has the diamond segments

and the plastic around it.

- [Narrator] The belt saw is Diamond studded teeth,

will slice out almost 30,000 square feet of limestone

before needing replacement after 375 hours of operation.

Cutting with diamonds is a simple principle.

To cut something hard, it takes something harder.

And diamonds are one of the hardest materials known to man.

- Diamonds of cells are the cutting tool.

They're just like the teeth on a saw.

Powder itself, what holds the diamonds in

but the diamonds do the cutting.

- [Narrator] The powder in this case,

20% carbide and 80% cobalt is mixed with the diamonds.

Cold pressed into shape

and then hot pressed to form a hardened segment.

As these diamond infused segments cut stone,

the cobalt carbide alloy slowly wears away.

Continually exposing fresh diamonds at the cutting surface.

- The diamonds sit in through the segment

and as this segment wears,

the diamonds stay sharp on the surface of the segment

all the way through.

- [Narrator] The diamond segments are then braized

or soldered at high temperatures to steel mounts.

Heated to 1200 degrees, the molten silver solder fuses

the segment to the steel mount.

- It gets cherry red.

It has to melt the silver and you gotta work it around

and make sure that you have a good surface on each one

so that it holds good.

'Cause as you probably can figure it

takes a pretty good hold because that stone...

Whenever it hits that stone

that's what does the cutting of the stone.

- [Narrator] The segments will cut everything

from limestone, to granite, to marble, to slate.

The segments are sharp,

but they wouldn't stay that way without lots of water.

The belt saw guzzles 50 gallons a minute.

It pressurizes the water in a labyrinth theme system

inside the hollow guide bar

and shoots it out beneath the belt

at 50 pounds per square inch.

The belt hydroplanes on the pressurized water reducing wear.

- [Eddie] It also allows the cuttings that we've created

to be flushed out so that we're not constantly

re-cutting the same old stone

and prematurely wearing out the belts.

- [Narrator] The computer controlled saw

will cut a 15 foot deep 70 foot long channel in eight hours.

- It's an auto saw.

You program it right there in that cut

and it'll go down all on its own, automatically.

Never you have to fool with it.

- [Narrator] After the saw has completed the vertical cut,

workers drill horizontal holes

and hydraulically split the rock along the bottom.

Removing the limestone and 50 foot long,

five foot wide, 15 foot deep sections.

Though the Meyers quarry saw his cutting edge,

it's merely the most modern application

of stone cutting techniques,

first practiced thousands of years ago.

The most prolific ancient stone cutters

were the Egyptians who worked extensively with limestone.

Metal saws, fashion of copper, bronze and sometimes iron

were used with sand or emery,

a cutting grit like modern day diamonds

to fashion blocks of limestone over 6,000 years ago.

- In order to get the abrasive particles

to stick to the edge that use a resinous substance

of some kind, you know, plant resins

to get those particles against the stone

or the material that they were trying to cut.

[cutting machines trilling]

- [Narrator] In stone mills,

a modern version of this abrasive fed cutting technique

was widespread before the advent of diamond studded

cutting teeth in the 1960s.

100 years ago, gang saws like these

at B.J. Hoadley Quarries, would've been fed with

an abrasive slurry of sand or silica

to enable them to grind through limestone.

Today, these old fashioned saws are still at work,

but they've been updated with diamond teeth.

- This is a rocking gang,

what they call lift gang.

And it lifts and hits lifts and hits.

And the slurry gets trapped

in between the segments and in the middle.

'Cause when it's cut and the first one will cut,

then the slurry will get trapped in between the segments.

And then the second one has cleaner spot to cut.

And it just carries it all out

to the end of the blade with water.

- [Narrator] At Indiana Limestone Company,

fully modern mill.

The job of slabbing stone block from their quarry

is accomplished by gigantic diamond belt saws.

- The blocks come directly from the quarry

looking just like this.

And the first wheel operation of fabrication that we do

is to slab them.

We use these narrow belt saws.

- [Narrator] Cutting 14 inches per minute,

this saw slices a block into seven slabs in one hour.

It works much like the quarry belt saw.

But uses a narrower cutting belt.

- The belt travels around in a circle

through the two big wheels hydroplaning across it.

It's about washing the slurry out,

allowing the diamond to dig next and dig next

and if the slurry is there, it can't do that.

- [Narrator] Once blocks have been slabbed,

they're run through an assembly line

of 40, 48 and 64 inch circular saws.

Tipped with diamond cutting teeth

and running at a surface speed of 10,000 feet per minute.

The stone is cut to last.

Phil Beyers and Eddie Brooking

have been brazing diamond teeth to saws

for more than 80 combined years.

- While we have a lot of mills in this area,

but we ship all over the United States.

Not only here, it's everywhere, Canada everywhere.

But this is what they call the home of the limestone.

- Limestone capital of the world

is what they bill it as.

- [Narrator] Rightly so, Indiana's limestone

is of the highest quality and most plentiful in the world.

The mill and quarry saws get down and dirty every day.

When you look at a saw,

what it's designed to cut is not always a obvious.

The basic wood saws, most of us recognize them.

Stone saw is a little less common and harder to place.

But this saw, for the surprising amount of power and speed.

It must be for something fairly serious and it is.

This is the MPower 6,300 oscillating saw

designed to cut bone.

A surgeon turns to the saw for large bone surgeries

like total hip and knee replacement

or for more delicate procedures

like anterior cruciate ligament or ACL repair.

- In several sporting activities,

the anterior cruciate or the front ligament

tends to be torn and can get torn.

What we need to do surgically speaking

is to replace that ligament with a separate tendon

that we harvest from the patient.

- [Narrator] The replacement tendon

will be anchored by two 10 by 25 millimeter bone grafts

harvested from the knee by the MPower 6,300.

This cordless $17,000 steel aluminum plastic saw

can accommodate over a hundred different types of blades,

tipped with serrated teeth

and covered in a hardened chrome coating

to reduce friction when cutting bone.

The saw's variable speed blade oscillating from a dead start

to 14,000 cycles per minute,

offers the surgeon increased control.

- That could start it up slowly just to score the bone

without much vibration or jump until I get it started.

[power saw revving]

And then I can go ahead and go for broke.

- [Narrator] The combination of a thin profile

yet stiff blade allows the surgeon

to plunge the saws tip directly into bone.

- The saw blade has depth marks on it.

And I can watch my depth marks as I cut.

- [Narrator] In an actual surgery,

these bone were grafts would be screwed in place

to anchor the new tendon replacement

for the torn anterior cruciate ligament.

Ultimately, the greatest challenge

for surgical saws comes after surgery.

When they're cleaned and then run through an autoclave,

a device that uses steam to sterilize equipment.

- The autoclaves run at about 272 degrees Fahrenheit.

So looking at that, you have to have electronic components

that can withstand that type of heat.

Go through their hundreds of cycles a year

for each handpiece.

And then still focusing on getting it to work each time.

- [Narrator] For all but the most recent history

of medical saws germs were unknown

and sterilization was not practiced.

- The early physicians knew that cutting off a limb

was really the only way to save a patient's life.

There were no antibiotics.

There was no nothing else you can do to avoid sepsis.

So even going back to Greek and Roman times

amputation was an operation that was carried out.

- [Narrator] A surgeon would've given this 1730s,

German amputation saw only a cursory cleaning.

- Sterilization came in at the end of the 19 century.

So essentially they would take this saw

from patient to patient without cleaning it.

And that was one of the reasons why infection

killed far more people than the surgery itself.

The friend of the surgeon in those days was speed.

The faster you could get the limb off the better

because patient didn't tolerate it very well.

And it would be used to saw back and forth

on a patient's arm or leg while two assistance

or more were holding the patient down.

- [Narrator] Though, this practice must have been brutal,

it's even harder to imagine the use

of the earliest medical saws, prehistoric stone instruments.

- The earliest civilizations, thousands of years ago,

used saw like instruments made from flint stones

actually to cut into bones

and even do potentially brain surgery in the skull.

- [Narrator] Trepanation, sawing

or boring holes in the skull is one of the oldest surgeries,

dating back as far as 6,500 years.

The practice was widespread among the Inca and Maya.

And was accomplished by abrasion,

cutting and drilling techniques.

It speculated that these cultures performed Trepanation

to treat head trauma suffered in battle or accidents,

to relieve headaches for ritualistic reasons

And even perhaps to release evil spirits.

Today, trephination is still used

in some neurosurgical procedures.

This trephine set was handcrafted

in Philadelphia in the 1840s.

And would've been used to treat hematomas

or bleeding on the brain.

By cutting a hole in the skull,

the surgeon allowed blood to exit

thus relieving pressure on the patient's brain.

- The way that the trephine find would work

is there was a central pin

and the pin would slide in and out

to direct exactly where the cuts will go.

The trephine would be turned

and the cut made would be circular

to whatever depth was indicated.

And then the skull flap was then lifted with an elevator,

which is this instrument right here.

- [Narrator] Sawbones carpenter,

though it's unclear when these slang terms for doctors

enter the lexicon.

They derived from a surgical practice

that though ancient came into its own

as a result of modern warfare.

- Most civil war amputation sets have multiple thin blades

because they had to be traded out quite frequently.

There were over 30,000 amputations

in union forces alone.

Everything from fingers,

which the survival rate was quite good for

up to mid thigh amputations

where the survival rate was less than 50%.

Both from bleeding and trauma of surgery

and also infection which obviously set in

very commonly prior to the age of antibiotics.

- [Narrator] This early saw was called an osteotome.

It was made in the 1830s

by an orthopedist named Bernhard Heine.

- It is the first mechanical chainsaw.

And as you can see, is a bit unwieldy to use.

It's quite heavy.

It has to be directed to a very specific point

for the very small teeth.

And it was so expensive to make and to maintain

that I just don't think it survived very well.

- [Narrator] Medical saws come in a variety

of shapes and sizes, but they're not the only ones

whose purpose is to save lives.

[siren wailing]

When it comes to life and death,

you need a chainsaw that can cut through walls and roofs

in any rescue situation.

An earthquake,

hurricane

or fire.

[upbeat music]

Smoke is pouring from a burning building.

A firefighter is trapped inside.

- [Narrator] Each passing moment

cuts into his chances of survival.

- So we're making entry.

[glass crackling] [power saw revving]

- [Narrator] Though, this is just a training exercise,

it highlights the importance of one piece of equipment,

the Stihl Magnum Rescue Saw.

- That's all when it encounters something behind here

conduit, nails, two by four, four by four,

it cuts right through that with no problem at all.

We went in there with a quick extraction

and got him out here to safety.

All is good.

- [Narrator] Designed exclusively for rescues.

This saw can make repeated cuts through wood and metal.

This durability is what makes it special.

Now firefighters have used chainsaw since the 1950s.

This specialized type of power saw evolved slowly.

Chainsaw chains were prone to breaking

when they encountered extreme heat

and metals embedded in walls and roofs.

So for decades, firefighters relied mostly on axes

to chop out access and ventilation holes.

But this process could eat up valuable time

during a rescue effort.

In 1992 faced with these obstacles,

the Virginia Beach Fire Department sought the help

of the world's largest chainsaw manufacturer, Stilhl.

Stilhl's engineers designed a more durable saw

that could withstand the extreme heat firefighters face

when cutting ventilation holes.

The best standard chains

may have only a portion of the cutter dipped in carbide.

Whereas the cutting edge on the RDR

or Rapid Dural Rescue chain

is entirely covered in carbide

which gives the teeth greater impact resistance.

At the firefighters request,

saws designers also made modifications

to the body of the chainsaw.

- Our structural firefighting gloves

are big and they're thick.

So it's very difficult to grip the old starter handle,

so they develop this for us right here.

It's very easy to grab with your gloved hand.

Another thing that they did

was this wrap around handle right here,

this gives us ability to use it right or left.

Most chainsaws are right-handed saws.

So we needed that flexibility up on a roof or in a house

or somewhere where we need it right or left operation.

Another thing that you see right here is this front guard.

Basically what happens is when you're cutting

asphalt shingles, roofs that have tar in there,

the tar will strike the exhaust system and stick.

So they developed this guard that you see right here.

It's easy to clean up, protects us all and works very well.

[power saw revving]

- [Narrator] They are sharp, powerful and can be dangerous.

And when they're doing their thing,

it's often best to keep our distance.

But they do or bidding

helping us to shape our environment,

to build, to destroy and even to save lives.

And when push comes to shove, they can even make music.

[gentle lifting music]