Su You said: "Now we have got three points. The point where the small circle intersects with the left side of the horizontal axis is point A, the point where it intersects with the right side of the horizontal axis is point B, and the point where the big circle intersects with the bottom of the number axis is point C."

"Now we draw a ray from point A. Starting from point A, use a compass to take out five equal segments on this line to get point D."

"Connect point B and point D to get a line segment, and then draw a parallel line to the line segment at each scale point. Then the diameter of the small circle on the horizontal axis is divided into five equal parts. This is the equal division of any straight line that we have already learned.

Methods."

"The next step is the key. As long as we connect the scale between point C and point A and point B, and extend it until it intersects the small circle, we can also get four points one, two, three, four." "We only need to make and

The four symmetrical points on the other half of the small circle corresponding to these four points, plus A and B, make a total of ten points. These ten points just divide the small circle into ten equal parts."

"When you connect every other point, you get a regular pentagon, which means that these five points just divide the small circle into five equal parts."

After talking about connecting the line segments, sure enough, a regular pentagon appeared inside the circle.

Everyone below was amazed at how ingenious this method was, so the children took out rulers and compasses from their schoolbags and started following them in their notebooks.

After everyone had done it once, Su You asked them to divide a circle into seven equal parts and thirteen equal parts. After they were sure that they knew how to do it, he said: "You have been studying with me for so long, so the requirements for you cannot be the same."

Uncle Shi is the same as Grandpa Shi."

"You can't just know the method, you also have to prove why this method can divide the circle equally."

"You go back, teach this method to others, and then discuss how to prove this problem together. A little tip, you can start with three equal parts, and then consider the angle, you should get the simplest proof method."

Shi Tong seemed to understand a lesson, but Shi Fu's eyes darkened.

Looking at a group of children who were inexplicably excited, Shi Fu murmured: "They all understand now? Am I the only one who doesn't understand?"

Shi Tong was flattering: "Actually, I don't quite understand..."

Then Shi Fu slapped her hard on the forehead: "A bunch of kids can't compare to you and you have the nerve to talk?! If you don't understand, you won't be allowed to eat tonight!"

Shi Tong: "..."

After taking the photo of Shi Tong, Shi Fushi went to adjust the spring forging machine he brought.

The spring steel plate is almost the same as the spring steel plate used in the suspension device of later generations of automobiles, but it is reversed. The center is hung on the clutch driven wheel of the waterwheel through a connecting rod, the other two connecting rods are hung on both ends, and the two ends of the forging hammer are hung below.

The forging hammer is like a solid doctor's hat, with four round holes drilled around the iron plate and pierced through the four steel columns.

Steel columns are fixed around the base of the forging machine.

As soon as the machine starts rotating, the forging hammer can move up and down along the steel column, and due to the influence of the spring, it keeps jumping up and down during the movement.

After adjusting the height of the base, Shi Fu shouted to Su You: "Turn on You Baby, let's try the effect!"

A furnace had already been set up in Su You, and a few iron bars were thrown into it.

Soon the iron bar burned red, and Shifu took the iron bar with iron pliers and placed it on the seat of the forging machine.

Su You pulled down the clutch, locked it, and the machine began to move.

"Dang-dang-dang-dang...dang-dang-dang..." Shi Fu stretched the iron rod forward and backward on the forging bed, and in a blink of an eye he flattened the iron rod into an iron plate.

The forging hammer rose, and Shi Fu put the flattened iron plate into the fire and burned it again, then pulled out an iron rod and put it on, with a crooked smile on his face: "It works! It works great!"

Su You was also happy: "That's just right. Give me a few more sets of knives. There are many people in the family and one knife is not enough."

Shi Fu rolled his eyes at him: "Good steel is not so bad! I will teach you a trick today, watch out!"

Shi Tong also put several iron bars he brought into the fire: "Master, good steel should be used on the blade. Let me and dad show it to you today."

After re-adjusting the height of the base, Shi Fu placed the red-hot steel piece on the seat, while Shi Tong took a long-handled chisel like a small flat-blade axe. After banging it for a while, the steel piece was cut into thin strips as wide as the index finger.

Then Ishitomi began to forge several thick iron bars he brought. After forging them into sheets, he used a chisel to cut many holes on one side.

At this time, you can see the value of craftsmanship. The distance between each opening is almost exactly the same. Without years of practice, it would be impossible to achieve this step.

Clamp the still red iron piece into a vise, use small pliers to open the iron teeth staggered in two directions, and insert the thin steel piece originally cut into it.

Then put it into the furnace and heat it red, take it out and continue forging. The steel and iron will soon be forged into one.

At this point, Su You understood: "Wonderful, wonderful! What a great way to cut corners!"

Shi Fu rolled his eyes: "It's true to reduce materials, which one of your eyes saw me cutting corners?!"

Shi Tong muttered on the side: "With the forging machine, it really saves a lot of work. Master seems to be right..."

In any case, several pieces of iron pieces embedded with steel were soon completed. Shi Fu really saved materials to the extreme. After cutting the iron pieces into the size required for the knife, he also used thick iron and iron pieces to create the handle.

That part would rather spend a lot of extra labor than waste a single star of good steel.

The next step is fine-tuning, which can only be done manually.

The knife shape is quickly punched out, the blade is thinned and ground with a grinding wheel.

Grinding wheels are now extremely convenient to make. Because of the presence of water glass, you can use quartz powder or corundum powder, that is, jade sand, add certain lubricants such as graphite and copper powder, mix it with water glass, and press and roast it to make the desired shape.

Grinding wheels of any shape.

The main purpose of roasting is to react the water glass with carbon dioxide and produce partial porcelain.

In addition to grinding wheels, metal sheets can also be used as substrates and sprayed with a spray gun to obtain cutting sheets of metal and stone.

Water glass reaction products are acid and high temperature resistant, and the temperatures generated by grinding and cutting will not cause melting and desanding. This method is still used in later generations.

There is a large pot hanging on the grinder. There is a three-layer silk cover on the outlet of the large pot. Half of the cover hangs down. The amount of water can be controlled by the number of turns the cover wraps around the spout.

The Shi family and his son are still modifying the lathe with higher precision. Before the brass ball valve came out, they could only make do with this method.

The Shi family father and son began to sharpen the knife, while the children went to help make wooden knife handles and knife boxes.

In the evening, several sets of knives were created.

According to Su You's requirements, a set of knives includes five bone-cutting knives, picking knives, fish knives, slicing knives, and melon and fruit knives.

Each set of knives is stored in a wooden box, which is similar to the kitchen sets of later generations.

Su You took out the slicing knife and took a look. He saw that the boundary between the steel and the iron on the blade formed a regular wavy dividing line. He couldn't help but clicked his tongue: "It's completely different from the burning edge line. The craftsmanship of this steel inlay is really amazing."

It’s amazing! It can be described as exquisite!”

Shi Fu laughed so hard: "You really think you know everything, but you don't know this?"

Shi Tong explained with a smile: "Master, this is a scholar who turned to be a blacksmith. It is not unusual for him not to know the traditional craftsmanship. Master, this is called horse tooth inlay. Blacksmiths with a little skill in the Song Dynasty can do this. After all, steel is relatively precious.

Generally, ironworks will save on using it."

Only then did Father Shi think of another question: "You baby, you actually need five knives to cook a meal? I'm afraid the cooks in the palace are not as meticulous as you. You are the only one in Song Dynasty."

A portion?"

Su You danced with a large knife: "Tonight, I will let you taste the power of authentic Su's twice-cooked pork!"

The so-called Su's twice-cooked pork was a name chosen blindly by Su You, but it was actually the Lianshan twice-cooked pork in later generations.

The method of making twice-cooked pork is actually the same as that of ordinary twice-cooked pork. The difference is only in the knife technique. Ordinary twice-cooked pork is cut, while Lianshan twice-cooked pork is cut with a large blade.

The meat was brought by Shi Tong from the city. He knew that the master liked to scratch his mouth, and besides everything else, he must have brought several kilograms of fresh meat with him every time he came.

He said it was filial piety, but in fact he ate more than two suyous alone.

Cook the butt meat until just cooked, let it cool, turn it sideways, trim both sides, and then use a large knife to slice it from the top.

The sliced ​​meat is thin and large, almost the same size as an adult's palm.

Then put the meat slices into oil pan and deep-fry them, remove the excess fat, add bean paste, black bean paste, pickled ginger and stir-fry until fragrant, then add some soy sauce, spicy rice oil, add green garlic sprouts and stir-fry, add salt and it's ready.

The pot is gone.

Today we have guests. In addition to the ordinary dishes cooked by the group, Su You added this as a treat.

Hachigong came back to accompany the guests. When he saw the plate of twice-cooked pork, he said: "This meat slice is really big. If you don't have a bottle of good wine, it won't be enough for this dish. Hengzhi, should we drink citrus wine or osmanthus wine?"

Shi Fu was so happy that he frowned: "Hachigong, you have so much wine at home?"
Chapter completed!