Find a Suitable Spanner

 Dear Readers,

In the construction industry, one of the most commonly used tools is the spanner. This versatile tool is mainly used for gripping and turning fasteners like nuts and bolts. Spanners are tools made to give you a good grip and extra leverage when tightening or loosening rotary fasteners. Usually crafted from carbon steel or drop-forged steel, they come in a range of shapes and sizes to suit different needs.

Metric spanners (mm) and imperial spanners (inch) are both available, but the construction industry mostly uses the metric system. Metric spanners are labeled in millimeters (mm). The nominal size (e.g., M12) refers to the thread diameter, not the spanner size.

The best way to find the right spanner size is to measure the distance across the flat sides (AF) of the nut or bolt head with a measuring tool. If you don’t have one handy, you can refer to a size chart or use a general formula for standard bolts instead.

A general formula provides a good estimate for standard hexagonal metric bolts:

For bolts up to M14: Spanner size = (Bolt diameter × 1.5) + 1 mm.

(e.g., M8: (8 × 1.5) + 1 = 13 mm).

For bolts M16 and above: Spanner size = Bolt diameter × 1.5 mm.

(e.g., M16: 16 × 1.5 = 24 mm).

Spanners are essential tools in various industries including Construction, providing the necessary grip and torque to handle fasteners effectively.

TORQUE TABLE

 Dear Readers,

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

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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Bolt Torque Calculations

Dear readers in continuation with my previous post, Let us discuss about the “What torque should be given for the Bolts?”

The only way to properly determine the optimum tightening torque for a given application is to simulate the exact application. This should be done with a tension indicating device like Torque Wrench or Spanner. The widely recognized engineering formula is T= K x D x P

T=Target tighten torque
K= Coefficient of friction (nut factor / Slip Factor), always an estimation in this formula
D = Bolts nominal diameter
P = Clamp Load or Bolt's desired tensile load (generally 75% of yield strength)

Above Three factors affect how much tension occurs when a given amount of tightening torque is applied. The first factor is the bolt's diameter. Naturally M24 bolts take more force to tighten than M16 bolt. The second factor is the bolt's grade. It takes more force to stretch a 10.9 Grade bolt than it does to stretch an 8.8 Grade bolt because of the greater material strength. The third factor is the coefficient of friction often called as nut factor and it is always estimation.

Keep in mind this is only an estimated value. It may provide satisfactory performance, but it also may not. It is extremely important to realize that this tightening value is valid only so long as all of the aspects of the application remain constant. Don’t think if you are giving more torque means it is good for structure / application, because during the torque operation bolt will be stretched. If more stretched than required it may be broken. So each and every application should be evaluated on its own to determine the optimum torque value for each application. If you are not aware please refer the manufacturer recommendations & Technical specification or use above formula with contingency.

Co-Efficient of Friction / Slip factor or Nut Factor details will be followed my Next Post.

For More details about Torque Click Torque

Best Quote :"Never leave that till tomorrow which you can do today". Have a Nice Day

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

Best Quote. "Never leave that till tomorrow which you can do today" Have a Nice Day.