Bevel gauge-Combination Set-Try square-Sine bar-FITTER ONLINE NOTE

Angular measuring instruments

1)- Semi-Precision 

i)- Meany tools are direct and indirect angle measurement purpose used.

ii)- The most common instruments used to check angles.

iii)- There are Three types of semi-precision angular measuring instruments a)- bevel or bevel gauge, b)- universal bevel gauge, c)- bevel protractor. 

a)- Bevel or bevel gauge:- 

 i)- The bevel gauges cannot measure angles directly. 

ii)- They are, therefore, indirect angular measuring instruments. 

iv)- The angles can be set and measured with bevel protractors.

 bevel gauge

b)- Universal bevel gauge:-

i)- The universal bevel gauge has an additional blade. 

ii)- This helps in measuring angles which cannot be checked with an ordinary bevel gauge.

Universal bevel gauge

c)- Bevel protractor:- 

i)- The bevel protractor is a direct angular measuring instrument.

ii)- It has graduation marked from 0° to 180°. 

iii)- Angles can be measured within an accuracy  of 1° using this instrument.

Bevel protractor

2)- Combination set(Precision):-

i)- Combination sets can be used for different types of work, 

ii)- It is used for layout work, measurement and checking of angles.

iii)- The parts of the combination set has a (1)-Protractor head, (2) Square Head 

(3) Center head, and a (4) Rule.  

(1)-Protractor head:-

i)- The protractor head can be rotated and set to any required angle. 

ii)- The protractor head is used for marking and measuring angles within an accuracy of 1degree . 

iii)- The spirit level attached to this is useful for setting jobs in a horizontal plane.

(2) Square Head:- 

i)- The square head has one measuring face at 90 degree and another at 45 degree to the rule. 

ii)- It is used to mark and check 90 degree and 45 degree angles. 

iii)- It can also be used to set work pieces on the machines and measure the depth of slots.

(3) Center head and Rule:-

i)- This along with the rule is used for locating the center of cylindrical jobs.

Combination set

3)- Try square:-

i)- The try square is an instrument which is used to check squareness (angles of 90°) of a surface.

ii)- The accuracy of measurement by a try square is about 0.002 mm per 10 mm length.

iii)- Try squares are made of hardened steel.

iv)- There are two parts of the try square a)- Blade and b)- Stock.

v)- The try square has a blade with parallel surfaces. 

vi)- The blade is fixed to the stock at 90°. 

vii)- Try squares are specified according to the length of the blade 100 mm, 150 mm, 200 mm. 

viii)- The try-square is used to: 1)– check the squareness,2)– check the flatness,3)– mark lines at 90° to the edges of work-pieces,4)– set work pieces at right angles.

Try square

4)- Sine bar(Precision):-

i)- A sine bar is a precision measuring instrument for checking and setting of angles.

ii)- The principle of  a sine bar is based on the trigonometrical function.

iii)- This is a rectangular bar made of stabilized chromium steel.

iv)- The surfaces are accurately finished by grinding and lapping.

v)- Two precision rollers of the same diameter are mounted on either end of the bar.

vi)- The length of the sine bar  is the distance between the centers of the rollers.

vii)- There are holes drilled across the bar, because it helps in reducing the weight, and also it facilitates clamping  of sine bar on angle plate.

viii)- Sine bars are used when a high degree of accuracy to less than one minute is needed for 1)– measuring angles, 2)– marking out, 3)– setting up for machining.

ix)- Sine bar is not a self setting, its setting done by slip gauge on the work. 

Sine bar