Special Purpose Bolts

Dear Readers,

Typical examples of the bolt for special purposes are as follows:

Stove Bolt

A stove bolt has a round flat head which is beveled 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

Domed, enlarged head shape and Designed to keep bolt from pulling through suitable tool.

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.

Type of Bolts

Dear Readers,

Some of the most commonly used bolts are illustrated below: This would be very useful for all construction engineers.

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. It is used for Construction and machinery applications.

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 is 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, certain parts of locomotives and Wooden works.

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. 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.

For More Information about Grade of Bolt Click Here

For More Information about Weight of Hex Bolt & Nut Here

Unit Weight of Hex Bolt and Nut

 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.

Bolts and nuts can be made of various materials such as steel, titanium or plastic. The finish or plating on a metal bolt or nut affects its look and durability. Below are some common finishes and benefits:

• Zinc - Most common, low cost, resists corrosion and rust

• Nickel - Very hard finish, higher investment, good corrosion resistance

• Chromium – Bright finish, good rust and corrosion resistance

• Chromate – Adds color, shine, superior rust resistance

• Anodizing - Aluminum, hard oxide surface, excellent corrosion resistance

Generally purchasing of fasteners are in Kilograms instead of pieces. But we could not know how many numbers available per Kg. For construction purpose, Bulk purchase is advisable. Hence below count table will be useable. Counts are based on 50Kg

For More Information about Grade of Bolts Click Here

For More Information about Torque Clique Here

Hardness of Bolt

Dear Readers,

Generally the grades of bolts are starts from 4.6 to 12.9. Also known as Ordinary bolt (Commercial Grade),  HT Bolt (High Tension) & HSFG Bolts (High Strength Friction Grip). 

The bolt designation system is based on two numbers. The first number represents the ultimate tensile strength of the bolt, 400 MPa, 800 MPa or 1200 MPa respectively. The second number represents the point at which the bolt will permanently stretch. A 4.6 grade bolt permanently stretches at 60% of its ultimate, an 8.8 grade bolt at 80% and a 12.9 grade bolt at 90 % of its ultimate.

Technically it can be quoted that the first number is the tensile strength of the bolt material (N² )/100. 

The second number is = 1/100.(the ratio of the Proof (or Yield ) stress and the Tensile strength expressed as a percentage = 100.[Yield (Proof stress) /Tensile strength] /100

For Example the tensile and proof strength of the steel for a 8.8 bolt is therefore calculated as follows

Tensile strength = 8 X 100 N/mm² = 800 N/mm² and Proof strength = 0.8*800 * 100 /100 = 640 N/mm² (generally speaking 80% of 800N/mm2)

The lowest grade is 4.6, commonly known as commercial grade. Next comes grade 8.8, known as structural grade, and finally, the highest grade is 12.9, known as HT / HSFG bolt. 

Available grade of bolts are 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 9.8, 10.9 & 12.9

Generally foundation bolts are made from 4.6 or 4.8 Grade

Hardness of bolts are as follows

Torque for HT / HSFG Bolts

Dear Readers,Wish You a Happy Durga Pooja.

 

Based on my previous posts you may familiar with grades of bolt, torque of bolt, torque calculations and slip factors. However it is a real challenge in construction industry to determine the torque for bolts. Technically it is based on the applications. Some times client mentioned in drawings or you may get it from technical specifications but most of the times both are missed out. Given below is an ideal chart. This is one of my rare collections. Hope it will be very useful to all engineers.

 

For More Details about Torque Click my Previous Post Torque

For More Details about Grade of Bolts Click my Previous Post Grade

For More Details about Torque Calculations Click Calculation

For More Details about Slip Factor/Nut Factor Click Nut Factor

 

Best Quote: "Search a beautiful heart not a beautiful face. Beautiful things are not always good but good things are always beautiful".

Grade of Bolts

Dear Readers,

Being a construction engineer, we very often use the bolts. Generally the grades of bolts are starts from 4.6 to 12.9. Also known as Ordinary bolt (Commercial Grade),  HT Bolt (High Tension) & HSFG Bolts (High Strength Friction Grip).

The bolt designation system is based on two numbers. The first number represents the ultimate tensile strength of the bolt, 400 MPa, 800 MPa or 1200 MPa respectively. The second number represents the point at which the bolt will permanently stretch. A 4.6 grade bolt permanently stretches at 60% of its ultimate, an 8.8 grade bolt at 80% and a 12.9 grade bolt at 90 % of its ultimate.

Technically it can be quoted that the first number is the tensile strength of the bolt material (N² )/100. The second number is = 1/100.(the ratio of the Proof (or Yield ) stress and the Tensile strength expressed as a percentage = 100.[Yield (Proof stress) /Tensile strength] /100

For Example the tensile and proof strength of the steel for a 8.8 bolt is therefore calculated as follows

Tensile strength = 8 X 100 N/mm² = 800 N/mm² and Proof strength = 0.8*800 * 100 /100 = 640 N/mm² (generally speaking 80% of 800N/mm2)

The lowest grade is 4.6, commonly known as commercial grade. Next comes grade 8.8, known as structural grade, and finally, the highest grade is 12.9, known as HT / HSFG bolt.

Available grade of bolts are 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 9.8, 10.9 & 12.9

For More Details about Torque Click Torque

For More Details about Torqe Calculation Click Calculation

For More Details about Slip Factor Click Factor

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NUT Factor / Slip Factor

Dear readers, in continuation with my previous post, Let us discuss about the Coefficient of friction

The basic formula T = K x D x P stated earlier takes these factors into account and provides users with a starting point for establishing an initial target tightening torque. The K factor in this formula is always an estimate. That is the coefficient of friction, frequently referred to as the "Nut factor." / “Slip Factor “

The value of this factor indicates that harder, smoother, and/or slicker bolting surfaces, such as threads and bearing surfaces, require less rotational force (torque) to stretch (tension) a bolt than do softer, rougher, and stickier surfaces

If Surface is not treated Slip factor is 0.20

If Surface is blasted, any loose rust removed, no pitting than Slip factor is 0.50

If Surface is blasted and hot tip galvanised than Slip factor is 0.10

If Surface is blasted and painted than slip factor is 0.30

The most commonly used bolting K factors arc 0.20 for plain finished bolts, 0.22 for zinc plated bolts, and 0.10 for waxed or highly lubricated bolts.

For More details about Torque Click Torque

For More Details of Torque Calculation Click Tor-Cal

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TORQUE

Dear Readers,

Being a Construction Engineer, We often used a word "Torque" during tighten the bolts. Let us discuss about Torque.

Torque is a force that tends to rotate or turn things. You can generate a torque any time that you apply a force by using a wrench / Spanner. When you use a wrench, you apply a force to the handle. This force creates a torque on the nut, which tends to turn the nut.

Torque is a measure of the turning force on an object such as a bolt or Nut. For example, pushing or pulling the handle of a wrench connected to a nut or bolt produces a torque (turning force) that loosens or tightens the nut or bolt.

The torque units contain a distance and a force. To calculate the torque, you just multiply the force by the distance from the centre. English units of torque are pound-inches (lbf.in) or pound-feet (lbf.ft.); the SI unit is the Newton-meter (Nm); the Metric unit is Kilogram Force Meter (Kgf.m) / (Kgm)

Torque Conversion factors

Newton Meter (Nm) to Foot Pounds (lbf.ft) = [1Nm = 0.738 lbf.ft]

Kilogram Force Meter (Kgf.m) to Newton Meter (Nm)=[1 Kgm=9.80 Nm]

How to calculate the Torque and Torque Values  / Charts will be followed my Next Post

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