Nuts, Bolts and Its Types
A bolt contains two parts a shank and head. The cylindrical portion of the bolt is known as the shank. The shank is threaded at the tail end for a sufficient length so as to effectively engage with a nut.
The shape of the head is depended upon the purpose for which bolt is required. The nut is a type of a fastener which has a threaded hole in it. The nut is always used in joining with a mating bolt to fasten various parts together.
Types of Nuts and Bolts
Different forms and types of nuts and bolts are as follows:
- Form of Bolts
- Hexagonal-headed bolt
- Square-headed bolt
- Cylindrical or cheese-headed bolt
- Cup-headed or round-headed bolt
- T-headed bolt
- Countersunk-headed bolt
- Special Purpose Bolts
- Stove bolt
- Carriage bolt
- Hook Bolt
- Expansion bolt
- Foundation or rag bolt
- Eye-bolt
- Stud
- Forms of Nut
- Hexagonal Nut
- Square Nut
- Ring Nut
- Cap Nut
- Cylindrical or Capstan Nut
- Dome Nut
- Wingnut or Thumb Nut
1. Forms of Bolt:
Some of the most commonly used bolts are illustrated below:
Hexagonal-headed bolt
This is the most common form of a bolt and is used for general fasting purposes. The hexagonal head is chamfered at its upper end.
To prevent rotation of the bolt while screwing the nut on or off, the bolt-head is held by another spanner. A hexagonal-headed bolt illustrated in the figure.
Square-Headed Bolt
This bolt is commonly used when the head is to be accommodated in a recess. This recess is made of square shape so that the bolt is prevented from turning when the nut is screwed on or off.
When a square-headed bolt is to be used with its head projection outside, it is provided with a neck of square cross-section. This prevents rotation of the bolt. This bolt is commonly used in bearings for the shaft. A square-headed bolt is shown in the figure.
Cylindrical or Cheese-Headed Bolt
This type of bolt is used where projecting corners are unacceptable, and where the space for arranging the bolt-head is relatively limited. The rotation of the bolt is prevented by means of a pin inserted into the shank just below the head.
The projecting part of this pin fits into a corresponding groove in the adjacent piece. This bolt is commonly used in big ends of connectors, eccentrics, etc.
Cup-Headed or Round-Headed Bolt
This bolt is used when projecting are undesirable and where better appearance is required.
It is usually provided with a sung forged on the shank just below the head, as shown in the figure. To prevent rotation of the bolt. This bolt is it used in the construction of tanks and certain parts of locomotives.
T-Headed Bolt
This type of bolt is used for securing clamps, vices, and other accessories to the tables of machine tools.
The tables are provided with T-slots to accommodate the T-heads. The neck of this bolt is usually square in section to prevent rotation of the bolt A T-bolt is shown in the figure.
Countersunk-Headed Bolt
This form of a bolt is used where the head of the bolt must not project above the surface of the connection piece.
It may be provided with a snack or a neck to prevent rotation of the bolt.
2. Special Purpose Bolts:
Typical examples of the bolt for special purposes are as follows:
Stove Bolt
A stove bolt has a round flat head which is bevelled on the underside to fit a countersunk hole, it is provided with a slot on the head, as shown in the figure.
For screwing the bolt into a nut by means of a screwdriver. This is used for assemblies where precision is of no great importance, and it is desirable to have the head of the bolt flush with the surface of the work.
Carriage Bolt
This is used for fastening wooden parts together or for fastening metal parts to wood it has squared portion directly under the head to prevent rotating when the nut is tightened or slackened. A carriage bolt is shown in the figure.
Hook Bolt
The hook bolt, shown Fig. is used in semi-permanent fastening in concrete.
This is also used in cases where there is no room for a bolt hole through one of the pieces to be connected, or in cases where a bolt hole would seriously weaken a piece. So the hook bolt is used for attaching shaft hangers to the flanges of joists and girders.
Expansion Bolt
This type of bolt is used in attaching parts to brick, stone or concrete walls and floors hee bolt has an internally threaded split sleeve which is slipped into a hole made in the wall and then expanded by running in the screw. This is shown in Fig.
Foundation or Rag Bolt
The rag bolt, shown in Fig. is used for fixing into the stone concrete foundation, the head is wider at the bottom than at the top, and is led into a tapered hole.
The tapered head is cut in an uneven manner (jagged) and moulted lead or sulfur is poured into the taper hole to fill the space between the lead and the stone or the concrete as the case may be. Where great strength is required, four parallel bars or keys are used in addition.
Eye-Bolt
The eye-bolt, shown in Fig. is very commonly used for lifting purpose. It is screwed or turned inside a threaded hole on the top of the machine.
Electric motors and medium and lightweight machinery are equipped with one or more eye-bolt so that they may be readily lifted and moved by an overhead crane.
Stud
A stud is shown in Fig. consist of a plain piece of cylindrical steel which is screwed at both ends. It has no head like a bolt. The nut-end is threaded for a length slightly more than the thickness of a nut or nuts to be used.
The other end called the metal end. It is threaded for a length at least equal to the diameter of the stud. The stud is used in place of a bolt when a bolt. Stud is commonly used to cylinder covers engine cylinders.