Question 13

The Correct Answer is C **Explanation for Option C (Correct):** A "Jobbers Set" (or Jobber Length drill set) traditionally refers to a standardized, commonly used assortment of high-speed steel (HSS) twist drills. These drills are characterized by their standard length (the Jobber length), which is suitable for general-purpose machining. The most common and useful range for general workshop and manufacturing tasks spans the fractional sizes from **1/16 inch up to 1/2 inch**, typically incrementing by 1/64 inch. This range covers the vast majority of standard hardware and fastener sizes encountered daily. **Explanation of Incorrect Options:** * **A) A set of numbered size drills from 1 to 60.** This set is correctly referred to as a "Number Drill Set" or "Wire Gauge Drill Set." While useful, this range (covering very small sizes) is distinct from the general-purpose fractional Jobbers set. * **B) A set of lettered size drills from A to Z.** This set is correctly referred to as a "Letter Drill Set." It covers sizes between the larger numbered drills and the smaller fractional drills, but it is not the standard fractional set typically designated as a Jobbers Set. * **D) A set of fractional size drills from 1/2" to 2".** This set covers very large diameters. Drills in this size range are much less common for general-purpose use, are typically purchased individually, and are not included in the standard, defining set known as the Jobbers Set.