I started with a ship full of max-level veterans, and I'm just a complete noob.

At nine o'clock on the morning of the third day, Lao Sun rolled up his sleeves above his elbows and sat down at the worktable in the confidential cubicle, with the anode copper block removed from the magnetron in front of him.

Fang Xudong stood to the side, arms crossed, watching Old Sun examine the copper block for three whole minutes without saying a word.

"Master Sun?"

"Don't rush."

Old Sun didn't even look up. He lowered the lamp, letting the light cut into the inner wall of the third cavity at an angle. He squinted for a long time, then changed the angle.

"Form milling cutter".

He finally spoke, using his thumbnail to trace a line along the bottom of the cavity wall.

"Look at this curve. It wasn't milled out in one go. It was shaped in one go using a special forming tool with a curved surface. A few tenths of a millimeter of allowance was left at the corner, and then it was finished by hand."

Fang Xudong leaned closer to take a look.

How can you be sure it's handmade?

"The knife marks are unevenly spaced."

Old Sun turned the copper block under the lamp and pointed to an extremely fine spiral pattern on the inner wall.

"Look, this isn't the tool marks from a lathe, where the spacing varies. It's the result of a rotating grinding head pressing in by feel."

He then pointed to cavity number six, which was the cavity with a relatively wide slit, and there was a parallel pattern on the wall.

"It's more obvious here; the direction is different from the other cavities. It's probably because they found it was too narrow when it was milled out, so the fitter fixed it with a fine file, and then polished it with a grinding head afterward."

Fang Xudong pushed up his glasses, his expression shifting from curiosity to a complex admiration.

"So, this thing is half mechanical and half manual?"

"right."

Old Sun put down the copper ingot and wiped the copper dust off his hands.

"Large-scale work relies on machines, while precision depends on people. I can do it myself, but I need the blueprints for that forming milling cutter and good copper material."

"Speaking of copper..."

Jiang Ming interjected, walking over from the other end of the cubicle with a small piece of oxide residue that Fang Xudong had scraped off the inner wall of the waveguide yesterday.

"Old Sun, look at this break."

Old Sun took the thin, almost transparent copper shavings, held them in his palm and examined them under the light, then gently bent them with his fingernail.

"Oxygen-free copper".

He spoke with great certainty.

"On what basis do you make this judgment?" Fang Xudong asked.

"If the oxygen content of copper is high, the fracture surface will be dark, the ductility will be poor, and it will break easily when bent. This piece can be bent to this extent without breaking, and the color is a bright red without any bluish-gray tinge, indicating that the oxygen content is very low."

Old Sun put the copper shavings back into the aluminum box.

"This material is essential for high-vacuum welding; otherwise, air bubbles will form in the weld, and it will leak when a vacuum is applied."

Jiang Ming wrote on the appraisal report: The anode copper block is preliminarily identified as oxygen-free copper, with the specific grade to be confirmed by spectral analysis. The machining method is rough milling with a special forming milling cutter, followed by hand finishing by a senior fitter, with an accuracy of ±0.1 millimeters.

Fang Xudong put the small bottle of oxide residue into his tool bag.

"I took the spectrum back to the Institute of Physics and got the results in three days."

Jiang Ming nodded.

"The report will not be finalized yet; it will be added together with the spectral results and precise magnetic field measurements."

At 1 p.m., Jiang Ming returned to the testing station to check the readings for the 440th hour.

The five tubes remained stable, and the microammeter pointers returned to their positions, showing no abnormalities as yesterday.

Xiao Zhao meticulously recorded the data and calibration results every eight hours in his duty log.

"Sixty hours to go."

Xiao Zhao said something in a low voice, as if talking to himself.

Jiang Ming didn't respond. He simply drew today's data points on the graph paper and used a ruler to connect the five most recent points into a line segment.

Flat, level, as if measured with a ruler.

At 3 p.m., the security department's phone rang.

Jiang Ming answered the call from the next office. The flat-headed clerk's voice came through the receiver, speaking half a beat faster than usual.

"Jiang, there's been progress on the email exchange in September."

"explain."

Between September 12th and 14th, the foundry workshop's mailroom received three internal letters. The mailing list indicated that they were from the Technical Department, the Labor Union, and the Logistics Department, respectively.

Jiang Ming didn't interrupt, his fingers unconsciously circling the telephone cord once.

"We checked the letter from the technical department; the handwriting wasn't Liu Shouxin's. It was a normal parts drawing notification sent by a clerk in the technical department. The letter from the logistics department was also fine; it was a seasonal notice for labor protection supplies, and the sender and receiver matched."

"What about the letter from the union?"

"That's where the problem lies."

The officer lowered his voice.

"The handwriting in the registration column was very messy, with several words strung together, making it difficult to read. We checked the union's document dispatch log for September and found that no letters had been sent to the foundry workshop at all."

Jiang Ming remained silent for two seconds.

"In other words, someone slipped a note into the exchange envelope in the name of the union."

"Yes. I'm currently checking the entry and exit records of the union office that day, as well as the staff on duty in the postal sorting room."

"Tell me if you find out."

When Jiang Ming hung up the phone and returned to Workshop No. 1, his steps were heavier than when he left.

The Grey Pigeon line is tightening, and with each step it takes, it gets one step closer to the core of its factory area.

At 6 p.m., Xiao Zhao finished the last instrument calibration of the day and was preparing to put the standard resistance box back into the cabinet.

He suddenly stopped moving and glanced at the testing platform.

"Jiang Gong."

Jiang Ming looked up from the pile of reports.

"The microammeter of the 0.2 oz. is shaking."

Jiang Ming took three steps to the testing platform.

The slender pointer of the microammeter does indeed swing slightly on both sides of the scale, which is visible to the naked eye. The amplitude is small, but the frequency is irregular.

"When did it start?"

"I just noticed it when I looked back after finishing my work."

Xiao Zhao's voice sounded a little tense.

"The calibration during the previous eight hours was fine."

Jiang Ming bent down and stared at the watch face for more than ten seconds.

The pointer swings by about ±0.3 microamps, which isn't much, but it's annoying.

"Take the standard container again."

Xiao Zhao deftly connected the alligator clips of the standard resistance box to both ends of the microammeter and switched it to the calibration setting.

The pointer immediately and steadily pointed to the calibrated value without the slightest tremor.

"There's nothing wrong with the watch itself."

Jiang Ming straightened up and looked along the measurement line of the 0.2 oxonium oxide, from the anode lead-out end all the way down.

The 448th hour.

There are 52 hours left to go until the finish line.

His gaze fell on the string of terminals and solder joints in the middle section of the high-voltage line.

One of them is loose.

This isn't a major problem, but if it's not resolved tonight, there will be an inexplicable jitter data entry on the record sheet tomorrow.

The 500-hour life test requires data from every hour to withstand point-by-point review during acceptance testing.

"Old Sun."

Jiang Ming's voice wasn't loud, but the echo from Workshop No. 1 was loud, and Lao Sun heard it from the south end.

"They're here."

"Working overtime tonight, checking the live wiring."