Depth of fusion (penetration) is the distance that fusion extends into the base metal or previous pass from the surface melted during welding.

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**6) **The depth of fusion of a weld is known as

**Answer is:**

## Penetration

**Explanation:**

**Related ISRO Technician-B Fitter Question Paper - 2019 (Set - 1) with Answer Key**

**Answer is:**

### 55

**Explanation:**

The series of first 10 natural numbers is an arithmetic progressions with first tern as 1 and common difference 1.

So the sum of the series will be Sn = n/2 { 2a+ ( n-1 ) d } where n is the number of terms in the series, a is the first term and d is the common difference.

S10= 10/2 { 2(1) + ( 10-1 ) 1 }

= 5 ( 2+9)

= 5 ( 11 )

= 55

**Answer is:**

### Knurling

**Explanation:**

The operation of producing patterns on cylindrical external surface by pressing a tool is known as Knurling.

**Answer is:**

### Half round

**Explanation:**

The shape of a rasp cut file is Half round.

**Answer is:**

### 60 Degree Prick Punch

**Explanation:**

This punch is used for making witness marks is 60 Degree Prick Punch.