BEVEL PROTRACTOR - SKengineers

 

BEVEL PROTRACTOR -

Introduction to Bevel Protractor -

Bevel protractor is an instrument that we use for measuring the angles of the objects. We see people using it with various objects that include jigs. Whereas, this occurs when we produce engineering/machine drawings.

Bevel protractor is an instrument that has a graduated circular scale with one pivoted arm that is used for measuring or making off the angles.

This instrument is capable of measuring angles with a least count of 5′ or 5 minutes.

It is used to measure the angle of any workpiece. It is used for various objects like jigs.

Sometimes the Vernier scale in the bevel protractor has an attachment for giving a more precise reading.

Bevel protractor has a very vital role in mechanical architectural drawing.

General use of bevel protractor is decreasing due to the introduction of software like CAD.

The bevel protractor is used for testing the angles very precisely.

It is used for a variety of mechanical and engineering related applications.

Unlike a normal protractor, we adjust a bevel protractor for fitting an angle. Its base is present on the bottom side of the angle, whereas the blade moves to match the opposing side. Various bevel protractors will have a Vernier scale on them that normally exists underneath the degree scale.

Parts of Bevel Protractor -

Swivel plate -

The swivel plate rotates over the dial. This swivel plate has a Vernier scale which is integrated into it.

Magnifying Glass -

The swivel plate also has a magnifying glass present over the Vernier scale. This magnifying glass is used to see the value of the angles in the main scale and the Vernier scale more clearly.

Vernier Scale –

The Vernier scale is fixed on the swivel plate and it moves with the swivel plate. Vernier Scale gives the remaining angle in minutes. There are 60 minutes in 1 degree. This Vernier scale is added in the bevel protractor to increase the precision of angle measurement.

In the center, the Vernier scale has zero. The Vernier scale has 12 divisions on both sides of the zero and each division is 5 minutes. So there are 60 minutes on each side of zero on the Vernier scale.

Angle locking screw -

This angle locking screw is used to lock the bevel protractor at a certain angle so that after locking angle can be measured without any disturbance.

This angle locking screw stops the swivel plate from rotating with respect to the dial or dial scale.

Dial -

This is the base of the bevel protractor over which the other parts are present. The main scale or the dial scale is marked over this dial.

Dial scale -

This dial scale is the main part of the bevel protractor. It contains the graduated scale of angle from a value of   0 degrees to 360 degrees. In this graduated scale, every tenth degree is numbered.

This 360 degree is divided into four divisions each of 90 degrees.

Blade -

This blade is made up of high carbon steel. This blade is a tapered blade. This blade is either 150 mm or 300 mm depending on the bevel protractor.

When the blade is parallel to the stock the zero of the Vernier scale matches with the zero of the main scale or the dial scale.

One side of the blade has an edge of 45 degrees and the other side has an angle of 30 degrees so that 45 degrees and 30 degrees can be directly measured using these edges.

Blade locking screw –

A blade locking screw is available to lock the blade at a certain place. This screw is used when we set the required length of the blade with the surface of the workpiece.

Stock -

The stock is one of the contacting surfaces in the bevel protractor while measurement of angle. The stock is the integrated part of the dial. As it moves the dial also rotates with respect to the blade and the angle value is changed in the dial scale. The job or workpiece whose angle is to be measured is kept in contact with this stock on one side. The other side of the job surface whose angle is to be measured is kept in contact with the blade. The blade of the bevel protractor travels inside the slot present in the stock.

Working Of Bevel Protractor -

At first, the workpiece whose angle is to be measured is kept between the blade and the stock of the bevel protractor. One side of the surface of which the angle is to be measured is kept in contact with blade and the other side is kept in contact with the stock.

When the workpiece properly come in contact with the blade and the blade is properly placed on the workpiece, the blade is locked using the blade locking screw.

After that when the surface to be measured comes completely in contact with the stock and the blade, the angle is fixed using the angle locking screw.

Now we see the value in the main scale which coincides with the zero of the Vernier scale. The value which we read from the main scale gives the angle in degrees.

To be more precise the angle in the main scale which comes just before the zero marks of the Vernier scale is considered.

To get the angle more precisely we will now get the remaining angle in minutes. To do that we see the line of the Vernier scale which coincides completely with the line of the main scale.

After getting that line, we see the position of the line in the Vernier scale. Then the minute of the angle measurement is calculated by multiplying the position of the coincident line of the Vernier scale with 5 ( Five ).

Then finally the angle measured using the bevel protractor is noted in degrees and minutes.

In this way, we measure angle very precisely using the bevel protractor.

What is Bevel Protractor and Bevel Protractor Range?

A bevel protractor is an instrument that is graduated spherical protractor with one pivoted arm that we use for making off the angles. Sometimes the Vernier scales have an attachment for giving more precise readings.

It plays a very important role in the mechanical and architectural drawing, although its general use is decreasing with the availability of the modern drawing software or CAD.

The bevel protractor is useful for establishing and testing the angles to very close tolerances. It reads to 5 arcminutes and can also measure angles from 0 degrees to 360 degrees.

The bevel protractors have a beam, a graduated dial and a blade that has a connection with a swivel plate (with the Vernier scale) by the thumb nut and the clamp. When the edges of the beam and the blade are parallel, a small mark on the swivel plate coincides with the 0 lines on the graduated dial.

To measure an angle between the beam and the blade having an angle of 90 degrees or less. The reading might come from the graduation number on the dial indicated by the mark present on the swivel plate.

For measuring an angle of over 90 degrees, we have to subtract the number of the degrees as indicated on the dial from 180 degrees. However, as the dial is graduated from opposite 0 marks to 90 degrees each way.

How to Use Bevel Protractor?

Firstly, unscrew the large clamp on the front part of the protractor. It loosens the blade so that we can swivel it.

Align the base of the protractor on one side of an angle, and then swivel the blade for making the other side of the angle.

Tighten the huge clamp.

Spot the zero on the Vernier scale. The Vernier scale is smaller on the inner side of the protractor.

Read the number of the degrees present on the main scale, directly above the zero present on the Vernier scale. For example, the zero that is on the Vernier scale lines up with the mark of 85 degrees.

Advantages Of Bevel Protractor -

1 It can measure angle very precisely up to 5 arcminutes and can measure angle up to 360 degrees.

2 It gives a very accurate measurement.

3 It is used to establish and test to bear angles in very close tolerance.

Applications of Bevel Protractor -

1 Bevel Protractor is used to check V Blocks.

2 It is used to check the inside bevelled face of the ground surface.

3 It is also used for measuring acute angles.