How to Check a Square for Accuracy | Step By Step Guide

Precision and accuracy are two qualities that carpenters cannot afford to compromise while executing their daily chores in line with their profession. That is why every carpenter should know how to check a square for accuracy and

Any attempt to overlook these critical aspects will lead to the production of substandard products which will subsequently lead to reduced customer loyalty if not the loss of customers.

To ensure a high level of accuracy especially in taking measurements and smooth surfaces, carpenters have numerous tools that facilitate this. One of the tools used by carpenters to attain accuracy is the square.

The square is designed in a way that it has one right angle and two straight edges. Its main purpose is to test the accuracy of the angles in the products designed by the carpenters; more specifically, the right angles. It thus must be very accurate so as to give the correct reading with minimal errors.

The square has two edges with one being shorter and wide while the other is longer and relatively thin. The two edges meet and form an angle of 90 degrees. Carpenters will always refer to the wide and shorter arm as the blade while the other one they call it the tongue. Carpenters have come up with several ways of checking the accuracy of their squares which include the following.

How to Check a Square for Accuracy

​How to Check a Square for Accuracy

How to Check a Square for Accuracy -Types of checking

Master Square

The master square is developed to test the accuracy of the working square by ensuring that the angle is actually measuring 90 degrees. The working square is mounted on the master square and the angle measurements are contrasted against those of the master square. The master square is made with high-level precision eliminating any room for gross errors.

The carpenter through use of the master square is able to make the necessary adjustments to his working square in case the two do not concur. This is one very effective way to check and correct any accuracy issues with your square to ensure you produce products that are of high quality.

Surface Plate with a Black Granite Block

For those carpenters that cannot access the services of a master square, worry not. The surface plate which is used handy with a black granite block that you hold by your knee is yet another solution to check the accuracy of your square.

You simply have to mount your square against the face of the block which is vertical and ensure that your blade is parallel to the surface plate. You then check through to see whether the blade is aligned with the surface plate and the tongue to coincide with the knee block. This way, you leave no room for errors with your square and you are guaranteed of accurate readings with the angles.

Straight Steel Edge

Steel as we know it is a quality metal element with a high degree of resistance to bending. It is for this reason that carpenters have decided to adapt the metal element to gauge the accuracy of their working squares.

What carpenters do is use a straight steel edge to draw a straight line on the surface using the blade of the square. Both sides of the blade are used and must produce coinciding lines when flipped over. This is the clear indication that the square is accurate and ready for use. If the lines do not become parallel, the square needs some adjustments before it is put into use.

Milling Machine

Carpenters who are lucky enough to access milling machines in their work environment can use the machines to counter check the accuracy of their squares before using them. All you need as a carpenter is to mount the square to the machine table then set the dial indicator by use of the spindle.

You are then required to slide the straight edges of the square against the straight edge of the milling machine. As you slide from one end to another, the two straight edges; that of the machine and the square must be in touch. If this is met, your square is good and ready for use.

Wooden Block

A wooden block that is well furnished can be yet another quick and simple solution to checking the accuracy of our squares. All you do is to clamp the square you are using against the edges of the wooden block and slide the square along the edges of the wooden block. The contact between the two should remain intact for any accurate square. If this is not the case, make the necessary adjustments to your square before commencing any work.

Plain Paper and Pencil

This technic is among the simplest ways to counter check the accuracy of any square by carpenters. You need a plain paper which you then place on a smooth surface, for instance, a table. You then take your square and align the blade to the edge of the table.

Using a pencil, draw a line on the plain paper with the aid of the tongue of the square. Once you are done, flip the square and align the blade to the other side of the table. Repeat the line with your pencil. The lines should be coinciding for any accurate square. The benefit of this method is it is fast, easy and convenient to all carpenters.


Producing the best output should always be our priority. As such, we ought to be keen and pay attention to details so that we use the correct tools and methods in our work. This is particularly vital to professions such as carpentry. A carpenter should ensure that they check their tools for accuracy before using them so as to ensure that the errors are not carried over to the final products.

The square, for instance, should be well counter checked through the various methods to eliminate any measurement errors for angles lest the carpenter produce products that are sub-standard. The carpenter should choose the technic that suits them as it may be hectic to acquire some of the tools of checking for accuracy in the square, for instance, the acquisition of the master square or the milling machine.

Alvin V.Stone

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