Slip Gauges Information

Slip gauges , types , materials, classification, application

1. Slip gauges Slip gauges or gauge blocks are the universally accepted standard for length. as they are introduced by Johansson, Swedish engineer ,called as Johansson gauges. They are working standard of linear dimension. They are used for main two purpose, For direct precise measurement where the accuracy of the work piece demands it. For use with high magnification comparator, to establish the size of the gauge blocks in general use. For checking an accuracy of measuring instrument

2. Slip gauges are rectangular blocks having cross section area 9mm Χ 30mm upto 10mm 9mm Χ 35mm above Or 10mm Χ 35mm

3. Shape : square & square with hole

4. slip gauges are available in Inch as well as in mm. Designation of slip gauge : For inch ‘E’ letter For metric ‘M’ letter b) On basis of number of slip gauges available in set. Inch sets = E81,E49,E41,E35,E28 Metric sets = M112,M105,M87,M83,M50,M33,M27

5. Classification of sets: Range(mm) Steps No of Blocks 1.001 – 1.009 0.001 9 1.01 – 1.09 0.01 9 1.1 - 1.9 0.1 9 1- 9 1 9 10 – 90 10 9 Total = 45 M45 (Normal set) Range(mm) Steps No of Blocks 1.001 – 1.009 0.001 9 1.01 – 1.49 0.01 49 0.5- 9.5 0.5 19 10- 90 10 9 1.0005 --- 1 Total = 87 M87 (Special set) Base dimension is 1 mm

6. M33/2 2mm base dimension set. ---less costly ---less likely suffer deterioration in flatness. Range(mm) Steps No of Blocks 2.005 --- 1 2.01 – 2.09 0.01 9 2.10 – 2.90 0.1 9 1 - 9 1 9 10,20,30 10 3 60 --- 1 100 ---- 1 Total = 33pieces

7. Wringing of slip gauges ---is thus defined as the property of measuring faces of a gauge block of adhering ,by sliding and twisting the gauge against measuring faces of the other gauge blocks or the reference faces of datum surfaces without the use of any extraneous means

8. Procedure for wringing Before wringing ,the slip gauges are cleaned by a lint free cloth ,a chamois leather or a cleaning tissue. On slip gauge is then oscillated slightly over the other gauge with alight pressure. One gauge is then placed at 90° to the other by using light pressure and then it is rotated until the block one brought in one line. As air expels out from mating faces gauge faces adheres with each other partly by molecular attraction & partly by atmospheric pressure, gap between mating surface is nearly about 0.00635 microns

9. Slip gauge set

10. Materials for slip gauges Slips gauges are made from Tungsten carbide – extremely hard wear resistant costlier Chrome plated -- Good anticorrosive property with stand against frictional wear. --If gauge worn out, can be again plated and brought to original size. -- Not possible to avail gauge blocks in wring together for longer time High grade steel -- hard ,economical

11. Slip are manufactured with exceptionally close tolerances Slip gauges are suitably hardened through out to ensure maximum resistance to wear. They are then stabilized by heating and cooling successively in stages so that hardening stresses are removed After hardening ,carefully finished by high grade lapping to a high degree of finish ,flatness & accuracy. For successful use of slip gauges their working faces made truly flat and parallel.

12. Classification according to the accuracy(class of work) Grades II : Grade II gauge blocks are workshop grade for rough checks. They are used for preliminary setting up of component where production tolerances are relatively wide; for positioning milling cutters and checking mechanical widths.

13. Grade I : used for more precise work such as setting up sine bars ,checking gap gauges and setting dial test indicators to zero

14. Grade 0 : These are inspection grade gauge blocks used in tool room and inspection department for high accuracy work. Grade 00 : These gauges are placed in the standard room and for highest precision work. Such as checking Grade I & Grade II slip gauges. Calibration Grade : This is special grade, the actual size of the slips calibrated on a special chart supplied with a set .the chart must be referred while making up dimension

15. Protector slip gauges In order to prolong life of slip gauges. Two protector slip gauges included in set of grade ‘O’,I & II ----Identified by letter ‘P’ ---- included in set of gauge blocks of grade O,I, & II ----Available in pair of 1 or 1.5 or 2 or 2.5 mm gauge block

16. Care of slip gauges General care: Protect all s/f against climatic conditions by applying suitable anticorrosive such as petroleum jelly. Keep slip gauges in suitable case ---separate compartment –close case when not in use. Protect gauges from dirt and dust. Should not magnetized other wise they will attract metallic dust Preparation before use: Remove protective coating applied to it with petrol Clean gauges with soft lint free cloth

17. Care in use : Fingering of lapped faces should be avoided Handling should be as minimum as possible Allowed to settle down to the room temp. 20 ° temp. Should not be held above the open case when being wrung together When not in use gauges should not kept on s/f plates for longer time with measuring face resting Standard procedure of wringing should be followed Wringing , any sign of roughness or scratching is felt then wringing should be stopped and faces examined for burrs or scratches.

18. Care after use : Gauges should not be left wrung together for an unnecessary length of time immediately after use …….. Calibration

19. Accessories of slip gauges