Types of Protractors
Protractors are instruments used to measure and construct angles. There are several common types of protractors, each with their own unique features and uses.
Basic Protractor
The most basic type of protractor is the manual circular protractor. This consists of a semicircular body marked with degree measurements, and a straight edge used to line up with the angle you wish to measure. Basic protractors are very affordable and easy to use. However, their accuracy depends on the user's precision when reading the angle markings.
Circular Protractor
Circular protractors have a full circular body and rotating arm. The advantage of a circular protractor is that it allows you to transfer angles and rotate the protractor around a drawing. Circular protractors are commonly used in technical drawing and construction.
Beam Compass Protractor
Beam compass protractors have a bar and movable discs which can be set to any angle. This type of protractor is more expensive but allows very precise angle measurements. Beam compass protractors are most often used in engineering and machining applications where accuracy is critical.
Metric Scale Protractor
Metric scale protractors have two sets of markings - one for inches and one for centimeters/millimeters. The metric scale allows for more precise measurement and work in the metric system. Metric protractors are essential for science labs and international use.
360 Degree Protractors
360 degree protractors, as the name suggests, have a full 360 degree range marked on the scale. This allows measurement of any angle, from 0 to 360 degrees. 360 degree protractors are useful any time full circle coverage is needed.
Digital Protractors
Digital protractors use electronic sensors and digital displays to precisely measure angles. Some digital protractors have additional features like built in levels, calibration, and the ability to hold angle readings. The advantages of digital protractors are:
- Highly accurate angle measurements
- Digital readouts for clear angle display
- Measuring features like hold, zero, and absolute/relative angle modes
- Durable solid state design with no moving parts
Digital protractors are commonly used for precision work in woodworking, mechanical trades, inspection, and anywhere that demands reliable and repeatable angle measurements.
As you can see, there are several types of protractors available, from basic manual models to high-precision digital protractors. The right protractor for you depends on your specific needs and application.
Basic Protractor
A basic protractor is the most common and affordable type of protractor. It can be found in any classroom or basic toolkit, and is used to measure and construct angles.
Design
The basic protractor consists of:
- A semi-circular body marked with angle measurements
- A straight edge used to line up with the angle
- A hole at the center for anchoring the protractor with a pencil point
The semicircular body is graduated with angle measurements, usually at 5 or 10 degree increments. The measurements start at 0 degrees on one side, and go up to 180 degrees on the other side.
Using a Basic Protractor
To measure an angle with a basic protractor:
- Line up the base of the protractor with one side of the angle.
- Anchor the center hole on the vertex point of the angle.
- Line up the straight edge of the protractor with the other side of the angle.
- Read the angle measurement from the scale where the straight edge intersects it.
To construct an angle with a known measurement:
- Draw one side of the angle, called the baseline.
- Place the protractor centered on the endpoint of the baseline.
- Mark the location on the protractor scale that matches the angle measurement.
- Draw a straight line connecting the vertex point to the angle mark.
Advantages
Basic protractors have advantages such as:
- Inexpensive and accessible
- Easy to use
- Lightweight and portable
- Durable
- Provides adequate accuracy for basic needs
With proper use, a basic protractor can provide angle measurements and constructions accurate to about 1-2 degrees, which is fine for most classroom and basic projects.
Limitations
The main limitations of basic protractors are:
- Dependence on user precision when reading the scale
- Difficult to get highly accurate measurements
- Not suitable for precision engineering applications
Overall, a basic protractor is an essential tool for basic measuring and drawing needs. For more advanced applications, other types of protractors may provide greater accuracy and capabilities.
Circular Protractor
A circular protractor is a more advanced, flexible type of protractor used for precisely measuring and constructing angles.
Design
The circular protractor consists of:
- A full circular body marked with angle measurements from 0 to 360 degrees
- A rotating arm that can be aligned to any angle
- A center hole and sighting marks for anchoring on a point
High quality circular protractors are made of durable transparent plastic with fine graduations for improved readability.
Using a Circular Protractor
To measure an angle with a circular protractor:
- Anchor the center hole on the vertex point of the angle.
- Align the rotating arm with one side of the angle.
- Read the angle measurement from the scale where the rotating arm intersects it.
To construct an angle:
- Anchor the protractor's center hole at the vertex point.
- Rotate the arm to align with the desired angle on the scale.
- Draw a straight line along the arm.
Advantages
Circular protractors have advantages such as:
- Full 360 degree range
- Rotating arm allows angle transfer
- High precision with fine graduations
- Clear markings are easy to read
The rotating arm makes a circular protractor extremely versatile - angles can be measured from any direction. This is useful in technical drawing, construction, engineering and other fields.
Limitations
Potential limitations include:
- More expensive than basic protractors
- Still relies on user precision for highest accuracy
- Large size not suitable for portability
Overall, a circular protractor is an essential tool when high-precision angle measurement and flexibility are needed. It offers greater accuracy and functionality than a basic protractor for technical applications.
Beam Compass Protractor
A beam compass protractor is a specialized, high-accuracy angle measurement tool used across technical fields like engineering, machining, and construction.
Design
The beam compass protractor consists of:
- A central bar or beam
- Two rotating discs that can slide along the bar
- Vernier scales for fine angle measurement
One disc is fixed to the bar, while the other can slide. The beam has precise angle graduations marked along its length. The vernier scale on the movable disc provides fractional degree measurements for added precision.
Using a Beam Compass Protractor
To measure an angle:
- Place the center point of the beam on the vertex of the angle.
- Align the fixed and movable discs with the angle sides.
- Read the angle measurement from the main scale and vernier scale.
To set a specific angle:
- Loosen the movable disc and slide it to the desired angle on the main bar scale.
- Lock the movable disc in place.
- Align the center point on the angle vertex.
- Draw along the discs to mark the angle.
Advantages
Beam compass protractors offer:
- High precision - accurate to 0.5 degrees or better
- Vernier scales allow very fine angle measurements
- Reusable - angles can be set and unset quickly
- Durable all-metal construction
This makes them ideal for engineering, manufacturing, construction and other fields where precision is critical.
Limitations
The limitations are:
- More expensive than basic protractors
- Bulkier size and weight
- Requires careful use and reading of vernier scales
Overall, a beam compass protractor is an essential precision tool for technical work. The high cost and learning curve may limit more basic users. But for applications demanding accuracy, the beam protractor's capabilities make it an invaluable instrument.
Metric Scale Protractor
A metric scale protractor is a specialized protractor marked with both standard inch graduations as well as centimeters and millimeters for metric measurement.
Dual Scale Design
The metric protractor contains two sets of graduations:
- A semi-circular scale in degrees, with markings from 0 to 180 degrees
- A straight metric scale in centimeters and millimeters
The inch scale is used to measure and construct angles in degrees as with a standard protractor. The metric scale allows direct measurement of length in centimeters or millimeters.
Using the Metric Scales
To measure an angle, align the center point and baseline edge as with a normal protractor. Read the angle from the inch degree scale.
To measure length along a straight line:
- Align the baseline edge of the protractor along the line segment.
- Read the length measurement directly from the metric scale.
No conversion or calculations are needed. The metric protractor allows you to seamlessly switch between inch angles and metric lengths.
Advantages
The dual scales offer several advantages:
- Single tool for both inch and metric units
- Instant conversion between measurement systems
- Essential for science labs and international use
- Versatile for math, engineering, arts, etc.
Students can work problems and experiments that mix both metric and imperial units. Craftspeople can transition between the two as needed. Overall, the metric scale protractor provides flexibility.
Limitations
Potential limitations include:
- Can be tricky for beginners to read two scales
- Not as precise as digital or vernier protractors
- Limited metric range compared to meter sticks
With practice, the dual scales become easy to use together. Overall, the metric scale protractor is an indispensable multi-purpose tool for today's mixed measurement world.
360 Degree Protractors
A 360 degree protractor is a measuring instrument used to measure and construct angles of a full circle or revolution.
Design
The key features of a 360 protractor include:
- A complete circular shape with 360 degree angle markings
- An anchor hole in the center
- A rotating arm for alignment
- Fine graduations down to 1 or 0.5 degrees
High-quality 360 protractors are made of durable clear plastic for visibility. Measurement scales may be marked in different ways for readability.
Using a 360 Protractor
To measure an angle with a 360 protractor:
- Anchor the center hole on the angle's vertex point.
- Align the rotating arm with one side of the angle.
- Read the angle measurement from the scale.
To construct an angle:
- Anchor the center firmly over the vertex point.
- Rotate the arm to align with the desired angle marking.
- Draw along the aligned arm.
Advantages
The key benefits of 360 protractors include:
- Ability to measure any angle from 0 to 360 degrees
- Versatility for a wide range of angle needs
- Precision with fine angle gradations
- Easy to use for transferring angles
This makes a 360 protractor ideal for math, science, engineering, construction and other technical work requiring full circle coverage.
Limitations
Potential limitations are:
- More expensive than basic half-circle protractors
- Large size not as portable
- Accuracy still depends on precise use
Overall, a 360 degree protractor is an excellent instrument whenever the ability to measure a full range of angles is needed. It provides flexibility not possible with standard 180 degree protractors.
How To Choose The Right Protractor For Your Needs?
Choosing the right protractor for your needs can be a daunting task, but here are some tips to help you make the right decision:
- Determine the type of angle you will be measuring and choose the appropriate protractor.
- Consider the level of accuracy and precision you need for your project when selecting a digital protractor.
- Look for models with an easy-to-read LCD and intuitive controls.
- Consider any additional features that may be useful for your particular application.
- Ensure that the protractor is compatible with your effective tonearm length if you are aligning turntables.
- If you are aligning a cartridge, choose a protractor that will help you get the overhang correct.
What Are The Different Types Of Protractors Available In The Market?
There are several types of protractors available in the market, each with its own unique design, working, applications, and advantages. Here are some of the most common types of protractors based on their design:
- Semi-circle Protractor (Half-Circle)
- Full circle Protractor
- Quarter Circle Protractor
- Square Protractor
- Miter Protractor
- Medical Protractor
- Bevel Protractor
- Single-arm Bevel Protractor
- Double-arm bevel Protractor
- Vernier Bevel Protractor
- Optical Bevel Protractor
- Universal Vernier Bevel
- Steel Protractor
- Digital Protractor
- Service Protractor
The choice of protractor depends on the application, level of accuracy, and precision required. For example, a digital protractor may be more suitable for applications that require high precision, while a steel protractor may be more suitable for woodworking and metalworking applications.
