Few Tips Help Buy Accurate Metric Tap Bolts

Machines as well as components, which are joined with screws and bolts, feature distinct torque specifications. Fasteners, such as metric tap bolts, are manufactured specifically to go through a nut/hole, which is pre-tapped to create a mating thread for that fastener. These rivets are designed to be conveniently used by any pneumatic tools or a wrench.

Metric Tap Bolt

How to identify metric tap bolts

People looking for these types of bolts may easily get confused with the American bolts. They are quite different in the measuring technique. While American bolts use the number of threads/inch as a measurement, the metric bolts use the distance between the threads.

Metric Bolts marked with Numbers to Indicate their Relative strength

These bolts are normally measured in millimeters as the standard reporting unit.

How to measure

The shank diameter of this bolt should be measured first, which is the distance from one side of the bolt to the other through the center

Metric grade to SAE grade Comparison

The number of threads should now be counted. Now the distance should be divided by the number of threads. For instance, if 10 threads make one centimeter, the thread length should be of 1 mm

The length of the bolt should be measured i.e. from the start of the head to the end of the bolt

Metric tap Bolt and Nut Technical Specifications

Now note the reading as such – diameter x distance between threads x length. For e.g. if a bolt has diameter of 2 cm, 1 mm between the threads and length of 25 mm then it would read as ¬†“2x1x25”

Torque Specifications

Like other fasteners, the metric tap bolts are also enabled with torque specifications. The torque refers to the total amount of force, which is required to turn the nut and bolt around a fixed point.

Internal and External Thread Graph of Metric tap Bolt

In the metric system, bolts are usually expressed as per their diameter, the distance between their threads. For e.g. a fastener with a size of 12×1.75×30 suggests that the fastener is 12 mm in diameter with a length of 30 mm and 1.75 mm of distance between the threads.

In the metric nuts, these bolts are categorized under various grades. However, the metric nuts do not have any identification marks and are rather listed by thread spacing and diameter.

Different Heads and Sizes of Metric tap Bolts

Low Grade Specification

A low grade 6 mm metric tap bolt features maximum torque values ranging between 3 to 5 foot-pounds. Similarly, a 8 mm bolt will feature torque ranging between 8 and 12 foot-pounds. And a 10 mm metric bolts will feature torque between 15 and 22 foot-pounds.

8.8 Grade mark Metric Hex Bolt

8.8 Grade Specification

A 14 mm metric tap bolt with a grade of 8.8 will require 101 foot-pounds of torque. A 16 mm of bolt will require 146 foot-pounds of torque. An 18 mm bolt requires 201 foot-pounds of torque and a 20 mm bolt requires 285 foot-pounds of torque.

Typical ISO bolt and nut Markings

FYI: The bolt torques are flexible and depends heavily on the lubrication of the bolt. The above mentioned specifications are for dry and unlubed metric bolts.

Dimensions of metric tap bolts


The shank or the threaded portion of the bolt is defined by the size. The shank’s diameter is usually used as the primary measurement. the length of the shank varies greatly with the width. Those two measurements are determined by suppliers like Mutual screw, to help customers identify the metric tap bolts.

Internal and external thread graph and specifications of Metric bolts

An M10x20 metric bolt is enabled with a 10 mm shank which is 20 cm long.


The diameter between the flat sections of the head is always 1.8 times more than the diameter of the shank. An M10 metric bolt with a 10 mm of shank will have a 16 mm of hex head. the shank size can be calculated by measuring the head’s dimension and dividing it by 1.8.

Specification Requirements of Metric Tap Bolts

How to buy metric tap bolts

These bolts are usually sold based on their length, width, thread size and diameter. Some of these rivets are also labeled as per their strength. In our store, these items are sold as per their size and coarse thread.

Before purchasing these rivets, always make sure your measurements are in metric units.

Mutualscrews Metric tap bolt

Few tips to help buy accurate bolts

#Always determine the diameter of the product, you’re willing to buy for your requirement

#The thread distance is the second factor to be considered

Various Sizes of Metric Tap Bolts

#After you’re done with diameter and the thread distance, it’s now time to look for the accurate length, your job requires.