1. CHAPTER 5 Use of Gage Block
DPT 312
METROLOGY
ROSHALIZA HAMIDON

2. Introduction
Gage blocks, first developed by C.E Johansson and also call Johansson blocks
Gage blocks are used as references for the setting of measuring equipment such as micrometers, sine bars, dial indicators. (for calibration)

3. Gage block

4. Gage block materials
The majority of gage block are made from hardened alloy steel.
Other materials used are; carbide blocks, chromium-plated block and stainless steel blocks.
The practical, functional characteristics of gage blocks are;
They must be made from something that can be accurately sized and finished
They must be stable and not change size of their own accord
They must be withstand considerable wear
They must be practical- affordable and wear corrosion resistant

5. Gage block grades
The major characteristics for choosing quality gage blocks include:
Accuracy
Wear resistance
Surface finish
Dimensional stability
Thermal conductivity

6. Four basic grades of gage block
Grade 0.5 (formerly AAA)
Reference gages, for very high precision work
Grade 1 (AA)
Laboratory grade, for calibration of instruments and other gages
Grade 2 (A+)
Precision grade, for toolrooms and inspection
Grade 3 (A and B)
Working grade, use in production

7. Size and shape of gage block
The two most common shape of gage block are rectangular and square
Both are available in thicknesses from 254 μm to 508 μm in several series
We usually purchase blocks in sets of one or more series
The number of blocks in a set varies among manufacturers, but sets are typically made up of 112, 88, and 45 for metric (121, 86, 56, 38 and 35 for English)

8. Three factors need to balance when choosing a set of block
Range of set
It is just a matter of choosing the appropriate range for your application
The number of combinations that require more than three blocks to form
A set of blocks will give you a number of options to form a given length
However, the combination in which you use the fewest blocks is always fastest and eliminates the chance for additional errors.
The number of people who will use it each day
With the number of blocks available, you can minimize the amount of time people spend waiting for the blocks they need
The larger the number of users, the larger the set should be

9. Gage block applications
At the lowest level of precision, we seldom use gage block in the place of rules
If we demand precision, we sometimes use gage blocks instead of vernier instrument and micrometer
Vernier instrument
We prefer to use gage blocks instead of vernier caliper when the part is more than 5 inches in length and instead of vernier height gage when the part is more than 10 inches in height.
Person in making measurement is not highly skill professional
Micrometer
Because micrometers require little skill to produce comparable results, you should use them only for measurement requiring no finer than 0.01mm discrimination up to 150 mm.
Beyond those limit, you may prefer gage blocks.
For measurements more than 200 mm, you should use gage block, but you must make the decision of which instrument to use based on practical consideration too.

10. Care of gage block

11. Wear blocks
Wear blocks are special blocks specifically used as reference surfaces at the ends of gage block stacks
It also use to protect the other gauge blocks and increase the life of gage blocks.
Wear block that have worn out can be replaced economically

12. Gage block nomenclature

13. Wringing gage block
Wringing (sliding and twisting motion) gage blocks together, which means combining them end-to-end to add their measurement values
The phenomenon of wringing gage blocks so they seem to stick together occurs for two reasons.
There is an adhesive action because of an ultra-thin film of oil or moisture between the blocks.
There is a molecular attraction or bonding, between the blocks because of the very flat and parallel mating surfaces. That’s why the better the block geometry, the better the wring will be.

14. Technique for wringing gage block

15. Combining gage blocks

16. Gage block holder
Gage block holders make it more convenient to use gage blocks, and they make your measurement reliable
The four advantages of gage blocks holders are:
They help us form combinations with uniform wringing intervals
They reduce the length change due to heat transfer
They make it more convenient to handle stacks of blocks
They help prevent costly damage to blocks

17. Gage block holder

18. References
Text book

19. Quiz What is the main purpose of using gage block? What is wear block?
What is wringing?
List THREE characteristics for choosing quality gage block
Give THREE rules for gage blocks care
Give ONE advantage of using gage block holder