The topstone is a primitive artificial grinder, and the lathe can be much more complex.

Shen Gui and Li Li met head to head, one person and one hand, holding the drawings handed down by Zhu Pingjin and watching.

"This top bed is dexterous, but this lathe is different, what is the difference between Craftsman Shen?" Zhu Pingjin asked.

Shen Gui pondered for a long time before replying: "Look at the flywheel hanging outward from this lathe is huge, it must be very difficult. The villain thinks that this lathe must be strong and durable. ”

Zhu Pingjin smiled: "It's natural to be strong and durable. But Shen Craftsman only knows its fur, but does not know its essence, so he has not yet started. ”

Hearing Shizi's criticism, Shen Gui was very ashamed. At this time, Li Li beside him raised his head and said: "This lathe has three clamps, one in the front and one on the front, and one on the side." According to the villain's guess, since the gun tube is to be made, the clamp connecting the flywheel end must be rotatable. The rotating fixture, along with the bearing and flywheel behind it, should be hollow so that it can easily hold an iron rod or drill several feet long. Of course, the drill bit can be fixed here, and the iron rod can also be fixed. The other end is the opposite. Between moving and immovable, the drilling can be completed. However, when drilling deep holes, it is most difficult to ensure that the deep holes are straight. The difference between the front and the front is a thousand miles. Therefore, the villain speculated that this lathe is not about the strength of the lathe, but about the accuracy! ”

Zhu Pingjin smiled. Li Li, Zhu Pingjin, didn't understand, only knew that he had studied, and had worked in the Wangfu Gongzheng Institute for seven or eight years, and his family was very difficult.

"What Mr. Li said is not bad. Can you tell us how to ensure the accuracy of this drilling? ”

This has the meaning of school examination. If the answer is correct, maybe the son of the world will look at each other with green eyes in the future. Wang Kunshan's eyes were red with jealousy, but he didn't know anything about it, so he had to hold back his heart and listen to how Li Li answered.

"The villain used to drill wood. This hand drill must be perpendicular to the surface of the wood. If there is a deviation, it must be deviated. If the deviation is found, it has to be scrapped and restarted, and it is not possible to try to correct the deviation. Why? The cover hand drill pipe is extremely long, and if it is forcibly corrected, the drill pipe is very easy to break. The iron rod beaten out of this iron is different in length, different in thickness, different in bend, and the end face of drilling is even more uneven. How difficult it is to drill a straight hole in such an iron rod! Therefore, the villain thinks that the thickness and length of the iron rod must be unified first, and then filed flat to make a blank that can be drilled, and then drilled! ”

Li Li already has the idea of simple industrial production. Highly subdivided types of work and reasonable and orderly processes are common phenomena in modern large industries.

"How do you make this blank of unity?" Zhu Pingjin did not relent. He wants to see what level this technical talent Zheng Anmin highly recommends.

"On the sketch of the lathe, there is a clamp at each end of the front and back ends. On the side of the bed, a clamp was also drawn. This fixture is used to fix the turning tool, and when you press the pedal, the clamp rotates with an iron rod, and the turning tool leans on it to turn the iron rod round. The same method is used to make round sticks made of wood. As long as you turn the stick with a rope bow and put the planer knife together, won't the stick be rounded? But the villain is puzzled, if this car knife can't move back and forth, how to ensure that the thickness of the iron rod is the same? Also, if the two ends of the lathe cannot move back and forth, how to feed the ...... of the turner"

Forgot to draw the bed rail, this is Zhu Pingjian's negligence. The straightness of the lathe guide rail is directly related to the accuracy of the lathe. Li Li found it, indicating that a three-dimensional image of a lathe had been formed in his brain. The screws, handwheels, and other parts that control the forward and backward movement of the turning tool and the feed are also not drawn. This is not Zhu Pingjian's negligence. He didn't know if he could produce a screw under the current production conditions.

Zhu Pingjin talked about the bed guide rail, put the problem of the screw out again, and asked his several skilled craftsmen if they could produce the screw.

Speaking of the screw, Shen Gui of the wooden work immediately retrieved the lost one just now.

"If this screw is just wood, it would be very easy to do! The screw is the chute on the log stick. Simply rotate the stick with a rope bow and use a narrow-bladed or sharp-edged hook knife to move the knife diagonally. When the hook knife is eaten into the wood, the twill will slide on its own with the knife holder. It's just that the slope of the hook knife can't be changed, and if it changes, the twill will be uneven......"

The sharp hook knife cuts out the triangular thread, and the narrow hook knife cuts out the trapezoidal thread. With the external thread, the internal thread of the engraved nut becomes very simple. Nail a broach to the end of the screw and pull the screw out of the round hole. There is a protruding pin in the round hole, which is inserted into the external thread of the screw, and when the screw is pulled, it is forced to rotate, and the broach carves the corresponding internal thread into the nut, which is exactly the same principle as rifling in guns. The old fitter called this method "with the metric mother, and the male and female cooperate (Note 1)". Since Shen Gui is a familiar hand, it will be easy to do. Zhu Pingjin took advantage of the victory to pursue, talked about the bevel angle and shape of the thread, as well as their respective characteristics and application ranges, and then instructed Li Li and Shen Gui to go back and slowly explore. This knowledge involves modern mathematics and mechanics, and Zhu Pingjin doesn't know how much the other party can understand when he talks about it.

After the lathe finished speaking, Zhu Pingjin took advantage of the fact that there was still time in the afternoon to step up the talk about steel. One is fried steel and the other is crucible steel.

Frying steel has been around in China for a long time, and it is an extremely primitive two-step steelmaking method. Iron smelting first, then steelmaking, is relatively close to the modern steelmaking method (Note 2). The iron-making furnace and the iron-copying pond are used in series, and the semi-continuous operation is initially realized. The molten iron is released from the iron hole under the iron-making furnace, and then the iron hole is plugged with earth, and the iron-making furnace can continue to be fed and produced. The molten iron flows into a square pond next to the furnace, and is quickly sprinkled with concentrate powder or sun-dried tidal mud powder, and several people stand on the side wall of the square pond and stir it in the molten iron with willow sticks, which can immediately fry mature iron, or fried steel. The dry powder of tidal sludge contains iron oxide and iron silicate, and the concentrate powder is iron oxide, which can be sprinkled into the molten iron to promote carbon oxidation and reduce the carbon content of molten iron. The shallow and wide square pond, coupled with the rapid agitation of willow sticks, can promote the contact between molten iron and air, promote oxidation, and accelerate the formation of wrought iron. This is similar to the air or oxygen blowing in modern converter steelmaking.

There are many advantages of fried steel: large output, simple and safe production, and low cost, so the steel on the market in Daming is mainly fried steel.

But frying steel also has big drawbacks. In addition to the difficulty of precise control of the composition, the biggest problem is steel slag, which cannot be ruled out. Steelmaking is not only a simple oxidation reaction, but also requires slag removal and purification. Pig iron liquid contains a large number of impurities such as silicon, calcium, phosphorus, sulfur, etc., silicon and calcium are useless, phosphorus and sulfur are harmful, and the carbon content must be controlled. Roasting steel turns pig iron into mature iron, and while reducing the carbon content, the melting point of molten iron rises. The melting point of pig iron is only about 1,200 degrees, and steel reaches more than 13,400 degrees. As for pure iron, it is more than 1,500 degrees. When the dry powder of tidal sludge and concentrate powder are added to the molten iron and stirred with a willow stick, the carbon content of the molten iron decreases, the melting point rises, and the molten iron immediately begins to condense, turning into a thick sesame paste that cannot be separated, and the molten iron and iron slag are completely mixed together and cannot be separated at all. The rapid agitation also caused a large number of bubbles to be mixed into the molten iron, and the carbonized fractured part of the willow stick was also mixed with the iron.

It is conceivable that this kind of shoddy fried steel, which contains a large number of iron slag impurities, can be used in the manufacture of gun barrels? Isn't that a blow up as soon as you put it on fire? Not to mention making drill bits that are more demanding than the barrel. The blacksmiths of the Ming Dynasty were well aware of the defects of fried steel, so the fried steel had to be re-forged (hot forging) repeatedly in order to barely meet the requirements for use.

At this stage, it is impossible for Zhu Pingjin to achieve a leap in steel quality by improving the process of frying steel. If he wanted to get high-quality steel, his only solution was to use cheap fried steel as raw material and carry out crucible remelting. Anyway, it's the nature of scientific research, and cost is not the main issue.

The use of crucibles in China has a very long history, dating back at least to the Han Dynasty. When Zhu Pingjin was in Ya'an, he also used the Yingjing sand vessel, a specialty of neighboring Yingjing County, to boil water and drink tea. The firing of this sand vessel is completed by smoldering in a crucible. Ordinary converter steel belongs to boiling steel, and crucible steel belongs to sedative steel, the oxidation reaction is sufficient, there are not many bubbles in it, and the slag removal is convenient, like the broth to remove blood foam, scoop off the steel slag on the surface. Because of the long reaction time, crucible steel can also be easily added with various beneficial elements as needed to produce steel for various purposes. However, in Zhu Pingjian's previous life, crucible steelmaking has been eliminated in large-scale industrial production because the output is too small and the cost is too high, and it is mainly used to smelt special tool steel in small workshops, or to do steel composition testing in laboratories. Heating is no longer carbon, but electricity.

Steelmaking requires a high temperature of about 1,600 degrees, so the steelmaking crucible can not use ordinary clay crucibles, but can only be used in a small amount of clay to add a large amount of graphite or kaolin clinker to the special crucible. The melting point of natural pure graphite is as high as 3,600 degrees and 50 degrees, far exceeding the melting point of steel, and it is used in steel smelting without pressure. The graphite composition is pure carbon, which can increase the carbon content of the steel in small amounts during the steelmaking process. To increase the carbon content of the steel and make high-hardness high-carbon tool steel, graphite powder must also be added to the crucible. To increase the steelmaking temperature, preheated high-temperature air must be used in addition to coke with the right particle size. The high-temperature air can be heated by the heat dissipation of the furnace itself, or by a flame alone.

Zhu Pingjin talked in detail about the crucible steelmaking, and the Feng brothers' eyes popped out. There is an iron furnace handed down by his grandfather's grandfather in his Feng family's workshop, and they have been helping adults pull bellows by the stove since they were children, and they have also used crucibles to melt molten iron, but none of them know much about Shizi. Shiko's description is vivid, as if he had worked by the stove. But neither of them could figure it out, how could they be a lowly craftsman with the dignity of the prince?

Zhu Pingjin devoted himself to teaching his technique, and he has completely entered a state of selflessness. The feelings of the person being taught are not within his consideration. Metal materials science and its heat treatment is a broad and profound science, and it is also the basis of machining. In the absence of thermometers and modern heat treatment equipment, the operator's own experience must be judged.

For example, high-carbon steel and low-carbon steel, under the high-speed friction of primitive grinders such as gyros, the number of sparks flying out and the number of threads are different. The master can take the workpiece and pestle it on the grinder to make a roughly accurate judgment of the carbon content of the steel.

For example, the heat treatment of steel, normalizing, tempering, quenching, carburizing and other required temperature, time and cooling rate are also not close. Without a thermometer, you can only tell the color of the steel with your eyes.

Another example is that ordinary twist drill bits are generally made directly of high-carbon steel, rather than carburizing low-carbon steel. People who haven't really played it won't be able to figure out the difference between high-carbon steel and carburized low-carbon steel.

But these learnings from practice are difficult for Zhu Pingjian. He has worked at the grassroots level, from intern to master. Through systematic knowledge teaching, he let several people present have some basic cognition and take some shortcuts, instead of blindly groping in practice and wasting a lot of time to take detours.

Note 1: Convention. The male thread is male and the female thread is female. Why can't it be the other way around? Guess what.

Note 2: The modern steelmaking method adds solvents such as limestone to the molten iron, and then adds oxygen to blow to promote the oxidation and exothermic reaction, which greatly increases the temperature of the ladle. With high temperatures, there is high activity. In this state, desulfurization, siliconization, and phosphorus removal are relatively thorough. After the slag iron is separated, it is decarburized. Many comprehensive measures can greatly improve the quality of steel.