Equipments for Geometrical OR Alignment Tests

Equipments for Geometrical OR Alignment Tests

Equipments for Geometrical OR Alignment Tests -

(1) Dial Gauges Dial gauges are widely used for geometrical tests. The graduation on the dial need not be finer than 0'01 mm. The initial plunger pressure should vary between 40 and 100 g and for very fine measurements a pressure as low as 20 g is desired.

(2) Test Mandrel Test meandrels are used for checking the true running of the spindle.  Test mandrels are hardened, stress relieved and ground and made to a length which varies from 100 to 300 mm. Test mandrels/should be accurate and effect of natural sag should not be overlooked. To reduce the weight, hollow test mandrels may be employed. Two types of test mandrels arc used:

(a) Mandrels with a cylindrical measuring surface and a taper shank which can be inserted into the taper bore of the main spindle.

(b) Cylindrical mandrels which can be held between centres.

(3) Straight edges and squares Straight edge is placed on machined surfaces to check them, for flatness or straightness. Straightedges of cast iron or steel should be heavy, well ribbed and free of internal stresses. Their bearing surfaces should be as wide as possible.

Steel square is a precision tool used for laying out lines or for testing the squareness of two surfaces with each other. The error at the top of a standard square should be less that +0.01 mm, of a precision square less than +0.005 mm.

(4) Spirit Levels Spirit levels are used in the shape of a bubble tube which is mounted on a cast iron base.Two main types of spirit levels are:

(a) Horizontal spirit level

(b) Frame spirit level.

Horizontal Spirit Level

Frame Spirit Level

Spirit levels used for high precision measurements (tolerances: 0.02 to 0.04 mm per 1000 mm) should have a sensitivity of about 0.03 to 0.05 mm per 1000 mm for each division. A movement of the bubble by one division corresponds then to a change in slope of 6 to 12 seconds.

(5) Autocollimator Autocollimator can be used for checking deflections of long beds 10 horizontal, vertical or inclined planes.

(6) Alignment telescope Optical alignment telescope can be used t9 indicate errors of alignment in both the vertical and horizontal planes of the optical axis.

(7) Water levels Level measurement by means of water level surface and micrometer serves for measuring misalignments or inclinations of long beds and work tables. The micrometer holder is placed at various positions on the bed or table, and the micrometer spindle is screwed down until its tip just touches the surface of the water.

(8) Wavinessmeter Wavinessmeter is useful in recording and examining the surface waviness.