(Method) Following steps gives a brief of method of manufacturing of slip gauges :-
1. The high grade steel gauge blanks are taken with appropriate size.
2. They are subjected to hardened and rough grinding process.
3. Then they are subjected to a cyclic low temperature heat treatment, to provide stability of dimensions and to relieve the internal stress.
4. A batch of 8 blanks of similar nominal size is mounted on eight Co-planner Faces of a magnetic chuck.
5. Their one set of Faces is lapped truly flat by lapping process.
6. By changing the lapped faces on magnetic chuck, opposite Faces also lapped truly flat.
7. Now, the required Parallelism and equality of size is achieved by interchanging four of the eight gauges as shown in figure 1.8 (e). They are interchanged diagonally and turned end for end. Thus any errors in Parallelism are equalized.
8. Now, to determine whether the gauges are the required size they are removed from the chuck, wrong together in combination, and their aggregate size compared with an appropriate size master in a suitable comparator. A magnification of 8 is obtained in this calibration since, as each of the 8 gauges must be identical in size, the difference between combination and master may be divided by eight and this difference is distributed to each gauge.
9. If necessary, individual block can be mounted on chuck to bring their individual lengths within required accuracy.
- Air pressure applies pressure between the blocks because the air is squeezed out of the joint
- Surface tension from oil and watervapor that is present between the blocks
- Molecular attraction that occurs when two very flat surfaces are brought into contact; this force causes gauge blocks to adhere even without surface lubricants, and in a vacuum.
- Wiping a clean gauge block across an oiled pad.
- Wiping any extra oil off the gauge block using a dry pad.
- The block is then slid perpendicularly across the other block while applying moderate pressure until they form a cruciform.
- Finally, the block is rotated until it is inline with the other block.
- reference (AAA): small tolerance (±0.05 μm) used to establish standards.
- calibration (AA): (tolerance +0.10 μm to −0.05 μm) used to calibrate inspection blocks and very high precision gauging.
- inspection (A): (tolerance +0.15 μm to −0.05 μm) used as toolroom standards for setting other gauging tools.
- workshop (B): large tolerance (tolerance +0.25 μm to −0.15 μm) used as shop standards for precision measurement.
Uses of Slip Gauges:-
Slip gauges are important means of measurement in industries and laboratories.
Their uses are:
1. They universally accepted as a “Standard of length”.
2. They used for direct precise measurement where accuracy of work piece being measure is high.
3. They used with high-magnification comparators, to establish the size of the gauge blocks.
4. They are used for checking the accuracy of measuring instruments.
5. They are used to setting up a comparator to specific dimension.
6. They are used to check a batch of components quickly and accurately.
Care of Slip Gauges :-
Since the initial cost of slip gauges in high, so to maintain their accuracy, they require great care.
Following points should be kept in mind regarding the care of slip gauges:
1. When not in use, the slip gauges should be kept in their respective positions in the gauge box.
2. Before wringing the blocks together, ensure that their faces are perfectly clean.
3. Measuring faces should not be fingered.
4. Gauges should not be wrong together over an open gauge box, due to the possibility of accidently drop of any gauge on several gauges placed in the box and could be damaged.
5. Gauges should not be wrung together for a long time.
6. After use, does not break the pile but slide one gauge over the other to separate them.
7. After use, a thin layer of good quality grease should be applied on their faces, before they are kept in their case.
8. As far as possible, slip gauges should be used in air-conditioned rooms, free from dust and maintained constant temperature.
9. During the use, their working faces should never be placed on the surface plate etc.
10. Check accuracy at appropriate intervals.
11. Use minimum number of gauges for a combination.
12. Wring together in correct manner.
13. Use 2.5mm protector slips whenever possible.