Thread Vocabulary
The top point of an external thread or the bottom "valley" of an internal thread
What is the Crest?
The three standard methods for drawing threads are Detailed, Schematic, and this.
What is Simplified?
The "U" in UNC or UNF stands for this, the U.S. standard thread form.
What is Unified (or Unified National)?
A metric thread note always begins with this letter.
What is M?
This fastener has a six-sided head and is driven by a wrench or socket.
What is a Hex Head Bolt?
The bottom "valley" of an external thread or the top of an internal thread.
What is the Root?
This drawing method is the most "realistic" but is very time-consuming and clutters the drawing.
What is the Detailed method?
In the callout 1/4-20 UNC-2A, this number represents the threads per inch (TPI).
What is 20?
In M10 x 1.5 - 6g, this number is the nominal major diameter in millimeters.
What is 10 (mm)?
This fastener has a four-sided head and is common in rustic or heavy-duty applications.
What is a Square (head bolt/screw)?
The largest diameter of a thread. On an external thread, it's measured from crest to crest.
What is the Major Diameter?
This symbolic method, now considered dated, uses staggered straight lines to represent crests and roots.
What is the Schematic method?
The "C" in UNC stands for this series , while the "F" in UNF stands for this.
What is Coarse (UNC) and Fine (UNF)?
Unlike the Unified system, the number 1.5 in M10 x 1.5 represents this measurement in millimeters.
What is Pitch?
This is the machine tool used for cutting external threads.
What is a Die?
The distance from one point on a thread to the corresponding point on the next thread, measured parallel to the axis.
What is Pitch?
In the Simplified method, the minor diameter is represented using this type of line.
What are hidden lines?
This number represents the "General Purpose" class of fit, which is the most common one used
What is Class 2?
This tolerance grade number is the "General Purpose" grade, equivalent to Class 2 in the Unified system.
What is 6?
This is the machine tool used to form an interior thread.
What is a Tap?
A designation of the amount of tolerance and allowance specified for a thread.
What is Classes of Threads?
This drawing method is the "modern standard" and most common in the industry because it's the cleanest and fastest.
What is the Simplified method?
In 1/4-20 UNC-2A, the "A" means it is this type of thread , while a "B" would mean it is this type.
What is an External thread (A) and an Internal thread (B)?
A lowercase tolerance position letter, like 'g', indicates this type of thread , while an uppercase 'H' indicates this type.
What is an External thread (lowercase) and an Internal thread (uppercase)?
This is the unthreaded portion of a screw shaft, also referred to as the body.
What is the Shank?