NRA Metalworking & Woodworking for Gunsmithing 2 — Questions and Answers
Question 1: Which drill bit geometry is best suited for drilling into hardened steel during gunsmithing repairs?
- Standard high-speed steel twist bit
- Carbide-tipped or cobalt drill bit (Correct answer)
- Brad-point wood bit
- Spade bit
Correct answer: Carbide-tipped or cobalt drill bit
Carbide-tipped or cobalt drill bits maintain cutting edges at the high temperatures generated when drilling hardened steel.
Question 2: When silver soldering a front sight to a barrel, what is the correct flux application sequence?
- Apply flux after heating the joint
- Apply flux to cold, clean metal before heating (Correct answer)
- Apply flux only to the solder wire
- Flux is not required for silver soldering
Correct answer: Apply flux to cold, clean metal before heating
Flux must be applied to clean, cold metal before heating to prevent oxidation and ensure proper solder flow.
Question 3: What is the primary purpose of draw filing a metal surface?
- Removing large amounts of material quickly
- Producing a fine, smooth finish by dragging the file sideways (Correct answer)
- Creating deep grooves for checkering
- Hardening the surface of the metal
Correct answer: Producing a fine, smooth finish by dragging the file sideways
Draw filing involves pushing or pulling a file laterally across the work to refine and smooth a surface after regular filing.
Question 4: A gunsmith needs to tap a hole for a 10-32 scope base screw. What drill size should be used for the tap drill?
- No. 19 (0.166")
- No. 21 (0.159") (Correct answer)
- No. 25 (0.1495")
- No. 29 (0.136")
Correct answer: No. 21 (0.159")
A No. 21 drill (0.159") provides approximately 75% thread engagement, which is standard practice for 10-32 threads in firearm applications.
Question 5: Which wood grain orientation provides the greatest impact resistance for a rifle stock?
- Flat grain running parallel to the length of the stock
- Straight vertical grain running the length of the stock (Correct answer)
- Cross grain perpendicular to the stock length
- Burl grain for maximum density
Correct answer: Straight vertical grain running the length of the stock
Straight vertical grain (quarter-sawn) running lengthwise is strongest because wood fibers align with the primary stress direction during recoil.
Question 6: When case hardening a small steel part using pack hardening, what material is typically used as the carbonizing compound?
- Borax and salt mixture
- Charcoal or bone meal mixed with an energizer (Correct answer)
- Motor oil
- Beeswax and turpentine
Correct answer: Charcoal or bone meal mixed with an energizer
Traditional pack hardening uses charcoal or bone meal mixed with an energizer such as barium carbonate to introduce carbon into the surface layer.
Question 7: What is the recommended method for removing a broken screw that is flush with the surface in a firearm receiver?
- Drilling out with a standard bit immediately
- Using a screw extractor after center-punching and drilling a pilot hole (Correct answer)
- Welding a nut to the broken screw stub
- Applying penetrating oil and waiting 48 hours only
Correct answer: Using a screw extractor after center-punching and drilling a pilot hole
Center-punching to prevent drill wander, drilling a pilot hole, then using an extractor is the controlled method least likely to damage the surrounding receiver material.
NRA Metalworking & Woodworking for Gunsmithing 2
Which drill bit geometry is best suited for drilling into hardened steel during gunsmithing repairs?