Chapter 99 (2/2)

This kind of screw is made by hand. In the production process, the screw embryo should be forged first, and then the nail head and the round nail body should be hammered out on the embryo; Then, a saw is used to cut a groove in the nail head, and a screw plate called die is used to make threads.

The production process of this kind of screw is complex and expensive, so the early screws were sold by themselves, and ordinary people can't master the technology of processing screws.

However, Ferguson just mastered this technology, so under his leadership, the seven or eight blacksmiths worked hard for a whole day to make four one meter long pull rod screws and more than ten quenched steel pieces on hook cutters.

Shi Xiong didn't know how to pull the rifling at all. He only knew that the rifling of the later gun barrel was pulled out with special equipment. Where did he see the manual rifling equipment in the middle of the 18th century.

So this time, Lieutenant Ferguson opened stone bear's eyes.

The hook knife and the pull rod screw are fixed, and then the rifling can be pulled.

Although the diameter of the steel bar used to install the hook knife is slightly smaller than that of the barrel, the diameter of the hook knife is slightly larger than that of the barrel if the steel plate is added. So it takes a lot of effort to pull the hook knife. Because the hook knife is almost pulled from one end of the barrel to the other in a ”hard squeeze” way.

The hardness of the steel sheet is greater than that of the barrel, so whenever the hook knife is pulled from one end of the barrel to the other end, the hook knife will pull out a slide of grooves from the inner wall of the barrel.

Of course, under the fixed barrel, there is a very ”complex” linkage mechanism in this era, which is also another core part of the lathe. The function of this mechanism is to adjust the rotation speed of the barrel according to the length of the pulling distance.

Yes, although the barrel is fixed in the middle of the two guide rails, it can't move back and forth, but it can rotate.

When the workers pull the hook knife, along with the movement of the wooden sliding table, a tough ox belt is driven to hang on the sliding table, and the ox belt is connected with a small wooden pulley at the bottom of the broaching machine through a wooden pulley at the other end of the broaching machine.

When the sliding table moves, pull the cattle belt, and the cattle belt drives the small wooden wheel to rotate. And another small wooden wheel coaxial with the small wooden wheel will also rotate. This small wooden wheel also has a cow belt connected with another big wooden wheel. This big wooden wheel also has a coaxial small wooden wheel, and that small wooden wheel will also have a belt connected with another bigger wooden wheel

This is actually a very simple three-stage belt drive reducer. When the sliding table is pulled, three groups of coaxial wood wheels under the broaching machine are pulled by the movement of the belt. Because after three decelerations, the biggest wooden wheel turns the slowest. In addition, the coaxial small wooden wheels of the last group of wooden wheels are connected with the fixed barrel, so once the sliding table is pulled, the barrel will rotate at a very slow speed and uniform speed.

In this way, with the uniform rotation of the barrel, each time the hook knife is pulled, a female rifling with a certain degree of entanglement can be broached. When a female rifling reaches a predetermined width, the second rifling is pulled in another position.

This kind of manual wooden broaching machine was the most important tool used by the early American colonists to pull rifling. Even after the appearance of steam machinery, this kind of manual broaching machine was still used in a small range.

However, although the rifling of rifles in this era is not as easy as that of later generations to be pulled hundreds of times, if we want to pull out a qualified rifling, we have to pull it at least 20 times. So, it's a hard job.