It is a device which is used to measure the length in micrometers.

1. TOOL MAKER’S
MICROSCOPE
By:
A.PRASANTH

2. CONTENT
• INTRODUCTION
• PRINCIPLE OF MEASUREMENT
• CONSTRUCTION OR ELEMENTS
• WORKING
• EXAMPLE
• APPLICATION

3. INTRODUCTION
The tool maker’s microscope is a versatile measuring instrument which is
use to measure small and delicate parts by optical means without the
application of pressure. It is designed for:
Measurement of complex form e.g. - profile of external thread, tool, templates,
gauges, etc.
 Measuring Centre to Centre distance of holes in any plane.
A variety of linear measurements.
 Accurate angular measurements.
It can measure upto 1 micrometre and 1 minute.

4. PRINCIPLE OF MEASUREMENT
• A ray of light from a light source is reflected by a mirror through 90˚.
• It then passes through a transparent glass plate.
• A shadow image of the outline or counter of the workspaces passes through
the objective of the optical head & is projected by a system of three prisms
to a ground glass screen.
• Observations are made through an eyepiece.
• Measurements are made by means of cross lines engraved on the ground
glass screen.
• The screen can be rotated through 360˚ the angle of rotation is read through
an auxiliary eyepiece.

5. Formation of Image

6. Main Components of Tool Maker’s
Microscope
1. Rotatable Table,
2. Measuring Stage,
3. Moveable Head,
4. Ocular (Eye piece),
5. Projection Screen,
6. Micrometres,
7. Objective Lens,
8. Prism.

8. CONSTRUCTION OF THE TOOLMAKER’S
MICROSCOPE
• The microscope consists of a rigid stand on which a moveable head is mounted.
• The measuring stage moves on ball guide ways by actuating two measuring
micrometers arranged perpendicular to each other in the length and the cross-
sections.
• The measuring range of each micrometer is 25 mm and the measuring capacity can
be increased using slip gauges.
• A rotatable table is provided over the stage, on which the work-piece can be fixed
either directly or between centres.
• This table can be rotated though 360 ͦ and the angular rotation can be read by fixed
Vernier.

9. WORKING
• The component being measured is
illuminated by the through light
method.
• A parallel beam of light illuminates
the lower side of work-piece which
is then received by the objective lens
in its way to a prism that deflects the
light rays in the direction of the
measuring ocular & the projection
screen.
• The direction of illumination can be
tilted with respect to the work-piece
by tilting the measuring head & the
whole optical system.

10. EXAMPLES
Pitch Measurement: -
• Take the hacksaw blade and mount on the moving blade of tool maker’s
Microscope in horizontal position.
• Focus the microscope on the blade.
• Make the cross line in the microscope coincided with one of the edge of the
blade.
• Take a reading on ground glass screen, this is the initial reading.
• The table is again moved until the next edge of the blade coincides with the
cross-line on the screen and the final reading takes.
• the difference between initial and final reading gives pitch of the blade.

11. Teeth Angle: -
• Place the blade on the table in same position.
• Rotate the screen until a line on the angle of screen rotation is noted.
• Take the angular reading, the initial one.
• Again rotate the screen until the same line coincides with the other flank of the
tooth.
• Take the final angular reading.
• The teeth angle of blade in the difference between the two angular readings.

12. APPLICATION
o Determination of the Relative Positions:
It is used for the determination of the relative position of various points on work by
measuring the travel necessary to bring a second point to the position previously
occupied by the first, and so on.
o Measurement of Angles:
Measurement of angles is possible in toolmaker’s microscopes by using a protractor
eyepiece.
o Comparison Measurement :
A toolmaker’s microscopes also do comparisons of thread forms, measurement of
pitch and effective diameter. In this case the comparison is done with master profiles
engraved in the eyepiece.
o Comparison with a Scale :
Comparisons of enlarged projected images with a scale tracing fixed projection screen
are also done in a toolmaker’s microscope.

13. KEY WORD’S OF TOOLMAKER’S
MICROSCOPE
Achromatic Condenser :
A combination of lenses made of different glass, used to produce images free of
chromatic aberrations is called achromatic condenser.
Projection Lens :
The lens that magnifies and transmits the object contour or image resulting from the
collimated parallel light rays for projecting rays of light over a screen. They are also
called condensing lens.
Magnification :
It is defined as the ratio of the screen diameter to the field diameter in a microscope.
Field Diameter :
It is defined as diameter of the area that can be projected on the screen.