Machine Design
In replacing the V-belts, a complete set of new belts is used instead of replacing a single damaged belt because

New and old belts will cause vibrations
Belts are available in sets
Only one belt cannot be fitted with other used belts
The new belt will carry more than its share and result in short life

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Machine Design
According to Indian standard specifications, 100 H6/g5 means that

Tolerance grade for the hole is 6 and for the shaft is 5
Tolerance grade for the hole is 4 to 8 and for the shaft is 3 to 7
Tolerance grade for the shaft is 6 and for the hole is 5
Tolerance grade for the shaft is 4 to 8 and for the hole is 3 to 7

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