Threads Study Guide – PLTW QUESTIONS AND
ANSWERS 100% CORRECT | LATEST UPDATE
2025
Sometimes called nominal diameter, this value is equal to the external diameter of
the threads. This value is needed to calculate the size of the receiving hole. -
ANSWER Nominal size
the number of full threads there are per one inch of shaft. This value (sometimes
shortened to its first letters) is used to calculate pitch. - ANSWER Threads per
inch
indicates the fineness of the threads. More fine threads require less force to
rotate into the receiving hole; however, they are more expensive to manufacture.
- ANSWER Type of thread (include UNC, UNF, and UNEF)
UN stands for Unified National (a standard that is applied to fasteners), with C
standing for course, F standing for fine, and EF standing for extra-fine. -
ANSWER UNC, UNF, and UNEF
a measure of fit between the mating internal and external threads. It is noted as a
number between 1 and 5 with class 1 threads having the loosest fit and class 5
threads having an interference fit. Class 3 threads are most common in general
applications. - ANSWER Class
Threads are either external (on the outside of the shaft, noted as "A"on thread
notes) or internal (on the inside of the receiving cylinder, noted as "B"on thread
notes) - ANSWER Internal/external designation
ANSWERS 100% CORRECT | LATEST UPDATE
2025
Sometimes called nominal diameter, this value is equal to the external diameter of
the threads. This value is needed to calculate the size of the receiving hole. -
ANSWER Nominal size
the number of full threads there are per one inch of shaft. This value (sometimes
shortened to its first letters) is used to calculate pitch. - ANSWER Threads per
inch
indicates the fineness of the threads. More fine threads require less force to
rotate into the receiving hole; however, they are more expensive to manufacture.
- ANSWER Type of thread (include UNC, UNF, and UNEF)
UN stands for Unified National (a standard that is applied to fasteners), with C
standing for course, F standing for fine, and EF standing for extra-fine. -
ANSWER UNC, UNF, and UNEF
a measure of fit between the mating internal and external threads. It is noted as a
number between 1 and 5 with class 1 threads having the loosest fit and class 5
threads having an interference fit. Class 3 threads are most common in general
applications. - ANSWER Class
Threads are either external (on the outside of the shaft, noted as "A"on thread
notes) or internal (on the inside of the receiving cylinder, noted as "B"on thread
notes) - ANSWER Internal/external designation
