Tool maker microscope

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 micro metre 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. Move able Head, 4. Ocular (Eye piece ) , 5. Projection Screen, 6. Micrometres, 7. Objective Lens, 8. Prism.

7. 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 .

8. 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.

9. EXAMPLES

10. APPLICATION 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. Measurement of Angles: Measurement of angles is possible in toolmaker’s microscopes by using a protractor eyepiece . 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. Comparison with a Scale : Comparisons of enlarged projected images with a scale tracing fixed projection screen are also done in a toolmaker’s microscope.

11. 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.