Little Engineer's Diary: Nuts & Bolts

Hi, there!!

Pausing my drawings a few days because of the my master thesis. But i'm again here with a new and amusing issue. Okey. I will commence to talk about nuts and bolts immediately! Alright. Initially, we must talk what's the nuts and bolts?

Bolts are the most widely used resolvable machine elements. The bolt is made by pulling a screw into a cylindrical bar. In principle it is obtained by helically wrapping a profile on a cylinder with equal pitch.The wedge effect is utilized in the anchoring process. Moreover, screws are the easiest way of the spinning motion translate to forward. The screws are normally right helical. In this circumstances, when the nut is turned clockwise in the bolt the connection is tightened, otherwise it is loose. The bolts and nuts run on the principle of force connection. Generally, forces of tension and compression in the axial direction compel the bolts.They are operated under tension forces(*).

What is the tension force?
We come to the most important issue that a material engineer should know. It is a common term used in strength calculations. Okay, but what is this?

Let's think of a simple bar. We will load forces which is parallel to the axis of the bar, equally magnitude and opposite to each other on both ends of this bar. If we want to calculate the tension in this bar according to the accepted method of sectioning, we will have to take a section from where the bar will be calculated. Let's take this section perpendicular. We will take into section the external force that affect. Thus, we will get single internal force impacting on parpendicular to the section. According to the equilibrium of the internal forces, the reaction force will be produced against action force. And both will be the same magnitude. This tensile force pair will compel the two surfaces of the cross section to seperate from each other, ie to pull one from the other. According to this compulsion, materials exhibit different fracture. We classify the materials as ductile / brittle according to shape of fracture. If the material shows elastic deformation and suddenly fracture, is brittle. But if material demonstrates waisting and plastic deformation, is ductile.

Let's go back.
Advantages and disadvantages of bolts&nuts
• Highly reliable operation
• Repeatedly removable and installable
• It is very easy to supply because it is completely standardized
• Manufacturing is easy and cheap
• Easy to replace
• Stress accumulation occurs due to geometry
• Sensitivity is not sufficient in some applications
• Thawing can be prevented, but loosening can not be avoided(**).

The bolts are classified according to the German Standardization Institute(DIN). Generally, St37, St42 and St70 steels are used. These steels are named according to the tensile strength. That is, the strength of St 37 steel in the 1 mm2 cross-sectional area is 37 kP / mm2 or about 370 N / mm2. Materials such as Al alloy, brass, teflon, polyamide are also used for various purposes bolts. If there is no big force in the manufacture of the bolts, St37 steel is usually used. St37 is a plain carbon steel.

About plain carbon steel
Low carbon steels involves cover the greatest amount of world steel production. Low carbon steel are used bolts, nuts, reformable machine parts and in construction sectors. The steels in this group are steel containing 0.20% carbon. In addition to, this steel also include components such as very few amount of Mn, Si, P, S. Their mechanical properties are limited. They are cheap and easy to shape. Their hardening ability is low.

It's okay here. Now let's look at my drawings.

6 corners shafts

Right-helix

How are we going to squeeze these machine elements?
Tightening and unscrewing of the bolt connections is done with a spanner or screwdriver. Wrenchs and screwdrivers are called according to heads or ends. I has draw a fork spanner and a flat screwdriver here.