What is the thread size of the heli-coils mentioned for replacement in the recording example?

What is the thread size of the heli-coils mentioned for replacement in the recording example?

• A. 1/4-28 inch
• B. 5/16-18 inch
• C. 3/8-16 inch
• D. 1/4-20 inch

Answer: (D)

Thread size tells you both the diameter and how many threads fit per inch. A helicoil provides internal threads, so you must choose the insert that matches the screw you’ll use with the part. In this recording example, the screw that fits the hole is a quarter-inch in diameter with 20 threads per inch, so the helicoil must be 1/4-20. Other options would mismatch either the diameter or the thread pitch (for instance, a finer 1/4-28 would require a different screw, and larger diameters like 5/16 or 3/8 wouldn’t fit the hole properly). So the correct match is 1/4-20.

Thread size tells you both the diameter and how many threads fit per inch. A helicoil provides internal threads, so you must choose the insert that matches the screw you’ll use with the part. In this recording example, the screw that fits the hole is a quarter-inch in diameter with 20 threads per inch, so the helicoil must be 1/4-20. Other options would mismatch either the diameter or the thread pitch (for instance, a finer 1/4-28 would require a different screw, and larger diameters like 5/16 or 3/8 wouldn’t fit the hole properly). So the correct match is 1/4-20.