48: Chapter 48 First Benchmark

On the eighteenth day, all the farmland was plowed and planted with crops.

When the final handful of soil was filled in, the red sun over the Wasteland was hanging halfway over the edge of the horizon.

Jiang Lin leaned on a military entrenching shovel that had worn down quite a bit, standing on the ridge of the field.

Sweat trickled down his dust-covered cheeks and into the corners of his mouth, carrying a salty and earthy, fishy taste.

The rough fabric of his school uniform stuck to his back, forming hard, crusty salt stains patch by patch.

"Hoo—"

He let out a long breath of stale air.

It was exhausting.

On this Wasteland without the aid of any modern agricultural machinery, turning the soil and planting relied entirely on a pair of hands...

If you put this workload into a short video from his era, it would at least have to be paired with a tragic BGM, and the title would have to be something like "A Record of Modern Youth Surviving in the Wilderness."

But here there were no bullet comments, no likes, only endless desolation and the iron law of having to survive.

On the nineteenth day, Jiang Lin gave himself a day off.

On the twentieth day, while eating baked potatoes for breakfast, he was already thinking about the workbench.

After resting the whole day yesterday, once his mind was cleared, early this morning, all those shelved problems popped right back up.

The low concrete platform against the east wall of the Stone House had an uneven surface; even with steel plates and aluminum shims for leveling, its overall rigidity was still insufficient.

When sawing or filing, the vibrations would transmit back through the table surface, affecting his feel.

He needed a better workbench.

What did a better workbench need?

First, sufficient rigidity.

Benchwork wasn't embroidery; when working, a person's entire body weight had to press down on it.

If the bench was as soft as a spring, all the force would be absorbed, and the workpiece couldn't be cut at all.

Second, sufficient height.

The clamping surface of the bench vise needed to be slightly lower than his elbows.

This was just like a cutting board for cooking; if it was too high, his shoulders would have to shrug up, and before long his shoulders and neck would be ruined.

If it was too low, hunching over all the time would be unbearable.

Third, sufficient stability, with the bottom unable to wobble.

The center of gravity had to be low, the base area had to be large, and ideally, it should grow together with the weight of the earth.

Fourth, it had to be buildable using the existing materials on the Wasteland and the tools he had brought.

He wrote these four points down on a piece of scratch paper, then began to take stock of his assets.

Among the steel plates brought from the Real World, a few were specially prepared for the workbench: two pieces of Q235 steel plate with a thickness of 8 millimeters, each about as big as the combined area of his two palms.

As for what could be found on the Wasteland—concrete chunks and steel bars from the ruins—he had accumulated these and placed them in the material pile outside the Stone House.

After eating the last bite of the potato, he drew a sketch of the combined structure on the scratch paper.

The structure of the workbench was divided into upper and lower layers; the lower layer was built into a solid foundation using concrete chunks and old steel bars, with a height roughly reaching the waist.

The top layer was paved with a flatly polished concrete slab to serve as the operating table surface.

Was stacking concrete chunks really stable?

This thing wasn't playing with Lego; the shapes of the chunks were bizarre and varied.

How they interlocked and how they bore force entirely depended on how they were arranged during masonry.

This was a problem that needed to be tested by hand, not one that could be calculated with a few formulas on a piece of scratch paper.

He tucked that piece of scratch paper into his logbook and got up to rummage through the material pile for concrete chunks.

The construction of the workbench took him a full three days.

He sorted the differently shaped concrete chunks by size and shape.

He picked out the ones that could be used to build the lower layer, putting the ones with slightly flatter surfaces on one side and the angular ones on the other.

According to the measured dimensions, he marked cross-shaped positioning lines on the floor inside the house, picked up a shovel to dig a shallow foundation, and then started building.

Without cement mortar, it relied entirely on dry stacking.

This required that every single chunk had to form a physical mechanical interlock with the others.

After stacking a layer, he would go outside to find a large stone with a flat surface, lift it up like a pile driver, and smash it down heavily.

He tamped it down repeatedly until those chunks were smashed so they no longer wobbled in the slightest.

Finally came the concrete slab.

The concrete slab was dismantled from nearby ruins, with an approximate volume of 60 * 40 * 15.

Of course, in reality it wasn't that regular.

But precisely because it was irregular, he dug out the Q235 steel plates and logs, using a board as a base and logs as rollers to make a simple inclined plane, and finally used a log as a lever.

It took him most of the day to transport it back, and he almost sprained his back.

To ensure the connection strength between the bench vise and the concrete slab, he ultimately used those two 8mm Q235 steel plates.

One was placed under the base of the bench vise, and the other was placed beneath the edge of the concrete slab.

Using a C-clamp, he clamped the base, upper steel plate, concrete slab, and lower steel plate together like a sandwich.

This was a stable static friction system.

As long as the pre-tightening force of the C-clamp was large enough, this structure would be as good as welded dead.

The bench vise base was re-leveled, the bubble of the level was centered, the bolts were tightened, and he shook it hard.

It didn't budge an inch.

It was as if it had grown into the Earth.

He stood in front of the workbench, placed his hand on the crank handle of the bench vise, closed his eyes, and felt the height.

His wrists hung down naturally, his elbows were slightly bent, positioned just a little lower than his elbows—perfect.

For the first day of training, Jiang Lin's goal wasn't to make things, but rather to process a piece of steel material to the extent that he could spot errors himself.

He took a flat piece of low-carbon steel out of the material area.

This thing wasn't very hard; it was two fingers wide, five millimeters thick, and about a palm and a half long.

[Fifth Wasteland Benchwork Training 001]

[Material: Low-carbon steel flat bar]

[Objective: Saw off a section, trim an end face, and attempt to establish the first datum edge.]

[Evaluation criteria: Do not pursue passing; pursue recording errors.]

The phrase "do not pursue passing" was very important.

If he thought about filing out a flat surface right from the start, the result would only turn into endless frustration and self-deception.

Today's purpose was to let the errors be exposed under the sunlight.

He took down safety goggles from the hook and put them on, without wearing thick gloves.

He could wear them to prevent cuts when moving rough steel materials, but when actually gripping the hacksaw bow or holding the file, it was actually unsuitable to wear them too thickly.

Thick gloves would act like a wall, cutting off the tiny force feedback between the metal and skin.

Moreover, when operating rotating or reciprocating tools, once a stray thread on the edge got snagged by a burr, the hand would be pulled into a dangerous zone.

He tied his cuffs tightly and completely cleaned up the excess screws, spare saw blades, and old hand-wiping cloths on the table.

The area in front of the sawing zone was left empty to prevent the hacksaw bow from hitting anything when pushed out.

The iron filings box was placed within easy reach on the right side, and the small cleaning brush lay obediently beside it.

Looking up, the [Tool Area Safety Rules] written in charcoal on a broken wooden board on the wall was facing him directly.

The first rule among them had been traced very thickly by him: [Eyes take priority over progress.]

Jiang Lin looked at it silently, lowered his head to clamp the flat steel into the bench vise, supported the material with his left hand, and turned the crank handle with his right hand.

The lead screw turned, and the jaws slowly closed, biting onto the steel material.

Feeling resistance, he didn't stop; he turned it another half circle and shook the flat steel hard with his hand.

There was a little bounce, which meant it wasn't clamped securely enough, and it would produce chatter during cutting.

He added another quarter circle.

Now it was stable.

Only then did he pick up the hand saw, install a bimetal saw blade, and tighten the wing nut.

Saw blade direction confirmed.

Teeth pointing forward, adjust the tension.

He flicked the saw blade with his finger, producing a crisp twang.

Neither too loose nor too tight, just right.

Jiang Lin took a deep breath and stood firmly in position.

His feet were staggered, with his left foot in front and his right foot in back, his center of gravity solid.

His left thumb gently pressed against the side of the line drawn on the steel material, with his fingernail touching the side of the saw blade as a guide, while his right hand tightly gripped the saw handle.

The first stroke.

Start sawing, push forward gently.

"Screech—"

The harsh metal scraping sound echoed in the Stone House.

It failed.

The saw blade didn't bite into the metal at all, but instead slid directly along the smooth edge of the flat steel, forcibly dragging out a dazzling white scratch two millimeters away from the marked line.

Jiang Lin didn't rush to push again; instead, he lowered his head and scrutinized the white scratch carefully.

His mind quickly began to review and analyze.

"Starting the saw slipped; the initial downward cutting force was insufficient, failing to form a groove on the surface of the material. Or perhaps the left hand's guidance wasn't stable enough and shook."

He found the position again, raised the hacksaw bow slightly, maintained a fifteen-degree angle, and rested his left thumb against it again, giving a very slight yet firm guiding force to the side of the saw blade.

Pull lightly.

Push lightly, feeling a little resistance.

Pull lightly again.

The scale on the edge of the flat steel was finally rubbed away, revealing a bit of silver-white, and a very shallow notch was ground out.

It was just a tiny notch, less than a millimeter deep.

Jiang Lin continued to maintain this angle and pushed lightly.

Click.

The feel changed; the saw teeth bit into the solid metal.

For a split second, he instinctively wanted to add force, wanting to saw this piece of iron open in one go.

Just as the muscles in his arms were about to press down, a movie-like flash appeared in his mind of that snapped saw blade during his first attempt.

Lateral stress, the saw blade snapped, the back of his hand hit the bench vise, and it swelled for two days.

He had almost fallen back into his old bad habits.

He immediately stopped moving and took a deep breath.

Push again.

Exert force when pushing, transmitting the body's weight along the arms to the hacksaw bow.

Relax when returning, simply pulling the saw blade back without adding extra wear to the tooth surface.

Try to make the hacksaw bow travel in a straight line.

Slash, slash, slash...

The metal produced a dull sound of being steadily cut, and the sound began to become rhythmic.

As the kerf deepened slightly, fine iron filings began to fall rhythmically like gray snowflakes.

He had been sawing for less than five minutes when his arms began to ache.

That persistent soreness that inevitably caused his movements to deform.

The first thing to fall into disarray was his shoulders.

In order to exert force, his right shoulder unconsciously began to shrug up.

Once his shoulders became disordered, the trajectory of his elbow joints followed suit, no longer being a standard linear reciprocation.

Once his elbows became disordered, his wrists unconsciously began to compensate for this deviation, trying to pull the saw blade back onto a straight line.

Disaster struck.

That kerf, which should have originally clung closely to the scriber's score mark, was deflecting outward at a speed visible to the naked eye.

He clearly felt that he was pushing straight, but in three-dimensional space, the entire saw frame had already undergone a slight tilt.

And the saw blade jammed in the gap, due to the distortion, emitted an extremely uncomfortable friction sound, as if screaming.

Jiang Lin stopped immediately, removed the hacksaw bow, lowered his head, and leaned in close to look at the kerf.

Sure enough, the kerf had deviated.

Viewed from above, a small included angle appeared between the kerf and the straight line he had originally drawn.

If he ignored this included angle and continued sawing, the entire section of material would definitely be sawed by him into an ugly slanted opening.

Jiang Lin stared at that gap for a moment without trying to correct it.

Forcing a change of direction in such a deep gap would cause torsional stress on the saw blade within the gap.

It would easily snap.

He put down the saw, picked up a pencil, heavily marked the direction of the deviation on the surface of the material, and drew an arrow.

He opened the logbook again to record.

[Error 001: After fatigue, shoulder and elbow trajectories turned into arcs, kerf deviated to the left.]

[Handling: Stop forced correction, retain the error sample.]

Recording completed, continue sawing.

This time, he deliberately slowed down.

After his movements slowed down, the problems instead popped up like bamboo shoots after a spring rain.

When fast, due to inertia, he naively thought he was doing a perfect linear motion.

Slowing down, he discovered that every single joint in his body was lying, betraying him.

His shoulders felt tired, wanted to save effort, and thus began taking shortcuts.

The elbow joint felt the angle was uncomfortable and wanted to steal a bit of angle.

Amid tiny vibrations, the wrist unconsciously adjusted the posture of the hacksaw frame.

Even the waist and knees were participating in this instinctive compensation of how to make things more comfortable.

This was by no means as simple a one-dimensional action as holding a saw and pushing it forward with the hand.

This was a complex human biological mechanism attempting to defy its own instincts, trying to make a thin, brittle saw blade move along a straight line that did not exist in an absolute Physics sense.

Jiang Lin suddenly understood a principle: the entry barrier to fitting might not be learning how to use a file and a saw at all.

But rather learning first to control this flawed physical machine of one's own, which always longed to slack off.

He closed his eyes and tried to break down his movements in his mind.

The shoulder joint provided a large range of displacement; it was the power source.

The elbow joint controlled the direction of propulsion; it was the guide rail.

The wrist joint was responsible for fine-tuning posture; it was the stabilizer.

The waist provided overall support, and the knees and soles of the feet controlled the shift of the center of gravity.

If any part exerted a little too much force or took a slight shortcut, the saw blade would immediately give the most honest answer.

Deviating from the path, getting stuck in the slit, vibrating violently, or snapping directly.

Having figured this out, his pace became extremely slow.

Every two minutes of sawing, he would invariably stop to check.

He checked whether the direction of the saw kerf had deviated again, touched the saw blade's temperature to see if overheating caused annealing, shook the workpiece to see if it was loose, and even checked whether the vise base was firm.

This caused the progress to be excruciatingly slow.

Sweating profusely, he sawed a short piece of low-carbon flat steel for nearly twenty minutes.

Until with a clang, a small piece of steel fell onto the floor covered with an old cloth.

He bent down to pick it up and let out a wry laugh.

The cut was pockmarked as if gnawed by a dog, sloping like a slide in an amusement park.

The end face was even more gruesome: high on one side, low on the other, and covered with rough burrs.

"How ugly!"

He couldn't help muttering a complaint to himself.

If this were placed in a metalworking internship class at a university in the Real World, handing in such an assignment would definitely result in being chewed out by the instructor and given a big failing grade.

Jiang Lin looked at it for a few seconds, but there was no disappointment in his heart.

This was his first real result today.

At any time, reality was more important than looking good.

He walked aside, picked up the vernier caliper, clamped both sides, and measured the difference in length.

Millimeter-level, the value was very small.

But it was enough to prove that the tilt he had seen with his naked eyes just now was not an optical illusion, but a solid Physics fact.

He quickly made a note in his notebook.

[Sawing completed.]

[End face tilt is obvious.]

[Length difference between both sides: approx. 1.8 mm.]

[Heavy burrs.]

[Physical stamina consumption: moderate.]

[Tool wear: saw blade not broken, tooth surface condition to be observed.]

Indeed, the saw blade not breaking was already a phased victory in his eyes.

After snapping five saw blades in the garage, he had already understood that before mastering the technique, not ruining the tools themselves was already progress.

Blanking finished, next came the main event.

Filing.

To put it bluntly, sawing merely separated the material; what truly imparted precision to the metal and turned it from a piece of scrap iron into a qualified part was filing.

Jiang Lin clamped the steel stock with its terrible edges back into the vise.

This time, the clamping position was much lower than when sawing, exposing only the end face that needed to be processed to prevent the material from bending and vibrating during filing.

He selected a medium-tooth flat file from the tool rack.

The length was appropriate, and the wooden handle rubbed his hand a bit raw.

Today's goal was very simple: to flatten this end face.

It did not involve complex curved surfaces, just a single flat plane.

He held the file handle with his right hand, pressed his palm against the end, and pressed the base of his left palm against the front end of the file.

Take a deep breath. Push.

"Squeak—"

The file awkwardly skipped across the end face.

It wasn't completely failing to bite into the metal, but it was close.

The sound was chaotic, harsh, and incoherent.

He knew the reason: he pushed too urgently, and the downward pressure given by his left hand was too heavy.

The front end of the file was pressed down low, resulting in a shiny scratch being heavily gnawed off near the outer side of the end face, while the inside wasn't touched at all.

Stop, look closely, record.

[Filing error 001: Excessive left-hand pressure, front end cutting too deep.]

Once more.

Adjust according to the posture in "Basics of Fitting".

When pushing the file out, the pressure of the left hand should gradually decrease, and the pressure of the right hand should gradually increase, keeping the file in a relatively balanced straight-line trajectory throughout the movement process.

Sounded like a simple linear equation with one variable.

But when you wanted to execute this equation with your flesh and blood, it was simply a disaster.

Every time it was pushed out, the force exerted by the wrist could not achieve a smooth and continuous linear change at all, but rather came in sections and pauses.

The wrist was like a sluggish valve.

Slowing down when it should decrease, pressing too much when it should press.

After filing back and forth for a dozen rounds, a large area of the end face was indeed polished bright.

But it was extremely unevenly bright.

The high spots were polished with a metallic luster, while the low spots still retained the deep marks sawed down just moments ago.

Horrible to look at.

This indicated that these dozen or so strokes of his merely shaved off a few of the most prominent high points, and there was still a Pacific Ocean separating him from true flatness.

He put down the file, grabbed a 90-degree square, and leaned it against the end face.

Look against the light.

The light arrogantly leaked out from the gap between the square and the end face.

One end leaked a lot, like opening a window, while the other end leaked a little, just a slit.

It wasn't bulging in the middle.

This time it was an inclined plane.

Jiang Lin put down the square and suddenly found it funny.

When practicing in the garage, no matter how he filed, he always ended up filing a convex surface high in the middle and low on both sides.

Now arriving at the Wasteland, when making his first benchmark block, he actually filed a perfect inclined plane.

Mistakes were truly colorful and never repeated themselves.

He didn't try to use great force to correct the inclined plane all at once.

That would only create new disasters.

He first picked up a pencil and drew the light leakage situation in his notebook.

A rough schematic diagram: high on the left, low on the right, messy filing marks in the middle, and thorny burrs on the edges.

Then he continued.

Filing was a hundred times more tormenting than sawing.

When sawing, you could at least see the saw kerf deepening bit by bit visibly to the naked eye, giving a sense of achievement.

But with filing, sometimes you pushed sweatily for a long time, leaned the square against it, and found that you had simply filed one mistake into another mistake.

Shrinking the inclined plane, the middle began to bulge again.

Shaving the bulge flat, the other side caved in again.

Always chasing balance, always breaking balance.

...

Working all the way until noon. When he stopped his hands, Jiang Lin felt that his right hand no longer belonged to him, the soreness rushing straight to his brain along the nerves.

The web of his thumb, where calluses originally grew, was rubbed red by the rough wooden handle of the file, hurting burning hot at the slightest touch.

Both arms were as heavy as if filled with lead.

He gently blew away the iron powder on the surface of the steel plate and removed this ill-fated workpiece from the vise.

After more than an hour of his repeated ravaging, that originally dog-gnawed cut had indeed changed drastically, filed into a face gleaming with a silver-white metallic luster.

Touched by hand, it was even somewhat smooth, and the edges no longer cut the hands.

Jiang Lin took a ragged towel from the side to carefully wipe the greasy sweat from his hands, and picked up the 90-degree knife-edge square once again.

Pressing the inner side of the square tightly against an unprocessed reference side of the steel plate, he gently pressed that sharp, straight knife-edge against the surface he had just filed out.

Aiming the workpiece at the light source of the dim LED low-voltage lamp overhead, he narrowed his eyes and stared at the place where the knife-edge and the metal made contact.

Light would not lie.

As long as there was even an extremely tiny gap, photons would stubbornly penetrate the obstacle and hit his retina.

Between the knife-edge and the metal surface, Jiang Lin saw an obvious band of light.

The middle was black, fitting completely.

While at both ends, the light leaked so brightly it was blinding.

He applied a little force with his fingers, and the square on that surface could actually sway slightly like a miniature seesaw.

"High in the middle, low at both ends. Going around in circles, it has returned to the convex surface."

Jiang Lin sighed with a wry smile.

He was very clear on the reason.

Because during the starting and ending stages of filing, to overcome inertia, his wrist would instinctively produce a downward pressing movement, causing a thin layer of metal to be filed away at both ends' edges.

The absolute plane defined by Euclidean geometry that he envisioned in his mind turned into a miniature hill in actual physical operation.

Unreconciled, he turned the steel plate over, changed to another direction, and measured it longitudinally.

This time, the light leakage situation became even weirder.

The left side leaked light, the right side didn't, and a few irregular light spots flickered in the middle.

What did this indicate?

It indicated that this surface was not only a convex arc surface, but also a three-dimensional curved surface with left-right tilt and pitted surfaces.

For the first time, he realized so deeply that the so-called plane was not as simple as looking flat.

It was a Physics rule forced out by squares, light slits, feeler gauges, and hundreds of failures.

And the current him hadn't even touched where the threshold of this rule was.

Wanting to carve this rule onto a stubborn piece of steel with bare hands was indeed very difficult.

After having a lunch of salt and pepper potatoes, Jiang Lin didn't return to the workbench to continue filing.

It wasn't because he didn't want to, nor was it because he flinched, but because he knew that continuing would be meaningless.

Fatigue would cause muscle control to plummet linearly, and movements would deform irreversibly. Once the movements deformed, every stroke he pushed out next would be adding weight to the existing mistakes, making the repairs worse and worse.

The Wasteland gave him time, but he couldn't waste time on pointless grinding.

Grinding hard to the end would only cause his mindset to collapse.

He placed the workpiece on an old cloth, took out his old mobile phone, and took a photo of it.

[Fitter sample: No. 001]

[Status: Unqualified.]

[Problem analysis: Starting to saw slipped, saw kerf severely deviated; unable to cope with biological energy-saving instincts during filing, leading to over-cutting at both ends, convex filing surface; complete failure in establishing the reference plane.]

After finishing this passage, Jiang Lin stared at the word "failure" for a long time.

In the past, when doing mathematics and Physics test papers, if a big question was done wrong, as long as one checked the answers, sorted out the derivation logic, and knew where the questioning point was and what it was testing, that question would be considered mastered.

But in the Real World of engineering and manufacturing, between understanding it in the brain and being able to make it with the hands, there lay a despairing gulf.

[Knowing the name of a mistake does not equal being able to correct it.]

In the afternoon, he put away the files and began practicing scribing.

In the eyes of many laymen, in fitting work, sawing off metal required strength, and flattening metal required skill, so scribing should be the simplest link, right?

Isn't it just holding a pen and drawing a line?

Jiang Lin used to think so too.

Just scribing: take a steel ruler, hold it down, take a sharp scriber, and draw a line along the edge of the ruler.

A three-year-old child could do it.

But when he truly stood in front of the workbench and pressed that steel plate ruler onto the waste flat steel, he discovered that things were simply not like that at all.

The steel ruler would slip.

No matter how much force you used to press it, on the slippery surface of the metal, subject to a slight lateral force, it would silently slip out by one or two millimeters.

The scriber would deviate.

The scriber was not a pencil with a soft tip; the scriber had a tungsten steel tip of extremely high hardness.

When sliding across, encountering resistance from the metal surface, if the wrist softened slightly, the needle tip would deviate from the edge of the ruler.

With the slightest change in pressure under hand, the drawn lines varied in depth.

The surface of this piece of material retained its black scale, along with tiny rust spots left from previous storage.

When the scriber passed over the black scale, the trace was clear.

When passing over a rust spot, the needle tip would jump, and the trace instantly blurred.

What made Jiang Lin feel most helpless was that he currently didn't have a truly reliable baseline edge at all.

The premise of scribing was that you needed a straight edge as a reference.

But the material in his hands had an edge that was already a defective product sawed crookedly and filed slantingly just now.

If you drew a line, no matter how straight, along an unreliable edge, you were merely extending the unreliability outward.

If the foundation was crooked, no matter how you built the building, it would be crooked.

Jiang Lin held the scriber, suspended in mid-air, and paused for a long time.

Finally, he helplessly put down the tools.

[Scribing premise: There must be a baseline edge first.]

[The current sample does not have a qualified baseline edge. Today, only scribing feel and force training can be done.]

He did not forcefully pretend that he could draw precise lines.

Instead, he rummaged through the material pile again to find a piece of flat steel that had not been sawed and whose edge was relatively straight compared to its factory state.

Selecting the straightest side, he tentatively designated it as the temporary baseline.

The steel ruler was pressed down.

The middle finger, index finger, and ring finger of his left hand spread apart and exerted force, pressing tightly against the ruler body like an eagle's talons to prevent sliding.

His right hand picked up the scriber.

There was a trick to holding the scriber; it wasn't the vertical posture of holding a pen, but rather tilting outward at an angle, with the needle tip closely pressed against the edge of the ruler.

You couldn't trace back and forth; tracing back and forth would make the line thicker, turning into a double line.

Try to complete it in one go.

He took a deep breath, held his breath, exerted force with his wrist, and slid uniformly along the edge of the ruler.

Screech—

A faint sound.

The line came out.

Very thin, very shallow.

Because of insufficient force, when the scriber reached the middle section, it was slightly tugged by a small rust spot, the needle tip jumped, and that line showed a visible slight tremor in the middle section.

Jiang Lin frowned and continued to scribe the second one.

This time, he learned his lesson and increased the pressure under his hand.

The line was indeed deeper, and the reflection was also very obvious.

But just as it was about to finish, due to excessive force, the tip of the scriber suddenly deviated from the edge of the ruler, abruptly scratching a short and ugly cross on the material's surface.

For the third one, the pressure control was poor, and the line was sometimes deep and sometimes shallow.

For the fourth one, because his left hand pressed for too long, his muscles relaxed, and the ruler slipped.

It slipped by half a millimeter.

Half a millimeter.

On past Gaokao exam papers, if a ruler slipped by half a millimeter, drawing an auxiliary line wouldn't affect the score at all.

But on machined metal, it was already a disaster-level mistake.

Jiang Lin stared intently at those crooked lines on the material, suddenly realizing like an enlightenment why that battered book listed scribing separately as one of the most important foundations of benchwork.

Scribing was not drawing pictures on paper.

Scribing was the first time visually transferring the absolute dimensions from the blueprint onto the rough actual material.

This was the first step from virtual to reality.

Once this step was transferred incorrectly, all subsequent sawing, filing, drilling, and connecting would be built on a wrong foundation.

Compounding mistakes with mistakes, the final assembled thing would definitely jam.

Especially on the Wasteland, under the condition that he didn't even have a bench drill at present, scribing appeared even more fatal.

Because he couldn't rely on precise hole positions to organize mechanical structures, he could only rely on edges, notches, clamping components, and old holes originally on the scrap material to piece things together.

Every line he scribed might determine whether several subsequent pieces of material could be correctly meshed together.

He let out a deep breath, put down the scriber, and picked up the center punch.

The center punch was a conical small iron rod used to punch a small pit at the intersection of the lines to facilitate the drill bit's positioning during subsequent drilling.

The tip aimed at the intersection of a certain line and the edge drawn just now.

His left hand pinched the center punch, his right hand picked up the small hammer, and he tapped gently.

Clink.

The sound was crisp.

Moving the center punch away to take a look, that point was too shallow; if a drill bit was applied, it would definitely slip away.

He put the center punch back to its original place, wanting to touch it up.

Tapping again.

Clink.

Taking it away to look.

Jiang Lin closed his eyes.

It missed.

During the second strike, the tip of the center punch did not perfectly fall back to the center of that extremely shallow pit from the first time, but instead deviated by a little under half a millimeter.

What should have been a perfectly circular small pit had now become a small oval resembling the number 8.

Jiang Lin looked at that oval center punch mark and was silent for a full minute.

[Center punch error 001: First strike too shallow, second strike return inaccurate, mark elongated.]

He suddenly felt that all day today, he was being humiliated by various low-level actions.

Sawing couldn't cut through, and was crooked.

Filing couldn't make it flat, and was slanting.

Scribing couldn't make straight lines, and shook.

Punching couldn't make accurate marks, and was vague.

Every item sounded dead simple.

But when it solidly fell into his hands, every item didn't obey the brain's command.

Towards evening, the light dimmed.

He no longer touched any metal.

Cleaning first.

This was also written in that book, part of the training.

Iron filings must absolutely not be swept by hand; they easily pierce into the flesh.

He used a small brush to sweep those gray iron filings on the workbench into the box on the right without leaving a single bit.

The file was brushed with a special steel wire file brush, cleaning the iron filings in the tooth gaps along the grain.

The saw blade was dismantled and wiped dry.

A thin layer of engine oil was applied to the file's surface to prevent rust.

The center punch and scriber were wiped clean and put back into the hard plastic box.

The lead screw of the bench vise was carefully checked with a rag once to confirm that no obvious grit had entered.

All tool areas were restored to their original positions from before work started in the morning.

The material area was covered with rainproof oilcloth.

After finishing all this, the sky on the Wasteland was completely dark.

The low-voltage LED lamp in the Stone House lit up.

The light happened to fall on the small wooden box at the bottom.

Lying in the box was his achievement for the whole day today: a piece of low-carbon steel that was sawed crookedly, filed full of potholes, scribed with trembling lines, and punched off-center.

If at this moment, someone from the Real World pushed open the door and walked into this Stone House, they would probably only find it ridiculous.

A dignified city-wide science top student.

A grinding expert who had lived for decades in a ghost place like the Wasteland and self-taught most of the undergraduate Physics system.

Tossing and turning here for a whole day, sweating a jin, made such a gadget that was even worse than junk.

But in Jiang Lin's heart, there wasn't a shred of feeling that it was ridiculous.

He knew that this ugly thing was the coordinate origin on his path of manual processing.

It was very important.

Starting today, he truly knew that he stood at the very bottom of this path.

After dinner, Jiang Lin sat in front of the stone table as usual.

He reviewed the few pages of training logs recorded during the day, organized his thoughts, and then turned on that precious laptop, clicking open "Introduction to Error Analysis".

This was the evening class he assigned to himself.

His current progress had already read to the second chapter.

The core concept was: when a physical quantity was calculated through a formula from several measured quantities that themselves carried errors, how on earth should the error of the final result be estimated?

He stared at the screen and read that famous formula.

The uncertainty synthesis formula.

In layman's terms, it was the uncertainty of each input quantity multiplied by its partial derivative with respect to the output quantity, then taking the sum of squares, and finally taking the square root.

If it were doing problems in the past, he would unhesitatingly memorize the formula and then plug in the data.

But now, he had a different thought.

He wrote down a specific example on the draft paper that had just happened during the day.

This afternoon, he filed that piece of flat steel, then used a try square to inspect the flatness of that surface, staring at the leaking light seam.

At that time, he wrote in the log: The light transmission amount is about 0.05 millimeters.

This was a physical measurement he made on the flatness of that filed surface.

But now, he asked himself, how much error was actually hidden in this 0.05-millimeter measurement itself?

He began to dismantle.

First, the eyes.

The sensor he used to judge the light transmission amount was his own eyes.

Under that dim light, the human eye's limit of resolution for light seams was roughly between 0.03 and 0.05 millimeters.

This depended on the angle of the light source, the angle of his observation, and even whether he was inattentive at the time because he was hungry.

He took an intermediate value, and the uncertainty of the eyes was approximately u1 = 0.04 millimeters.

Second, the try square.

That 90-degree knife-edge try square had a factory-rated precision of 0.02 millimeters.

However, this ruler had followed him through time and space, experienced the bumps of the Wasteland, was usually stored in a Stone House with huge temperature differences, and might have suffered slight bumps.

Its actual precision had definitely decreased.

He estimated a conservative value for this tool's uncertainty, u2 = 0.03 millimeters.

These were the two core sources of uncertainty. And they were independent.

Jiang Lin substituted these two numbers into the root-sum-square synthesis formula he had just learned.

Mental calculation could yield the result.

The square of three, the square of four, makes the hypotenuse five.

The total synthesized uncertainty of his judgment on the flatness of the filed surface was neither more nor less, exactly 0.05 millimeters.

Calculating to here, Jiang Lin's hand holding the pen froze in mid-air.

What did this mean?

This meant that when he narrowed his eyes this afternoon and swore that the light seam represented a 0.05-millimeter physical gap, after superimposing this plus or minus 0.05-millimeter system uncertainty, the actual true physical gap could be anywhere between 0 millimeters (completely flush) and 0.10 millimeters (a huge deviation).

Jiang Lin looked at the conclusion on the draft paper and didn't move for a long time.

When messing around blindly in the garage, he also used a try square to inspect the filed surface, looked at the light transmission, and then triumphantly wrote down in his notebook that the light transmission amount was about 0.05 millimeters.

At that time, he thought that was a number as definite as truth.

Until tonight, in this drafty Stone House on the Wasteland, after calculating this simple root-sum-square formula under the light, he suddenly came to a realization.

That was not a definite number at all.

That was just an estimate with a huge tolerance.

And before this, he had unexpectedly never thought about how wide the range of that tolerance actually was.

Jiang Lin took a deep breath, feeling as if something in his brain had been unblocked.

Closing the computer and turning off the light.

The Stone House plunged into absolute darkness and tranquility, Jiang Lin wrapped himself tightly in his sleeping bag, and closed his eyes.

Tomorrow, keep battling it out stubbornly.