UNIFIED NATIONAL COURSE UNC TAPS

Sutton Tools manufactures high-quality UNC (Unified National Course) thread taps designed for specialized engineering, automotive, and aerospace applications where custom or fine-pitch thread configurations are required. Here is the exact breakdown of what #8-32 means: 1. The "#8" Represents the Major Diameter The first number specifies the nominal outside diameter of the screw thread. For sizes smaller than 1/4 inch, the UTS system uses a numbering scale from #0 to #12. Physical Dimension: A #8 screw has a major outer diameter of 0.164 inches (approximately 4.17 mm). The Formula: You can calculate the diameter of machine screw numbers using the formula: Diameter =(Screw Number X 0.013) + 0.060 Diameter =(8 X 0.013)+0.060 = 0.164 inches 2. The "32" Represents the Threads Per Inch (TPI) The second number defines the thread pitch count. Thread Count: There are exactly 32 individual thread crests per inch of axial screw length. Thread Pitch: The distance from one thread peak to the next is 1/32 of an inch, which is 0.03125 inches (or 0.794 mm). 3. Thread Series Designation (UNC) An #8-32 thread belongs to the UNC (Unified National Coarse) thread series. It is the most common thread pitch for a #8 screw size. (By contrast, the less common fine-thread version is a #8-36 UNF). 1. Taper Tap (Starter Tap) The Taper Tap is designed to initiate the threading process. The Tip Chamfer: It features a long, gradual taper spanning 7 to 10 threads at the tip. The Purpose: Because of the long taper, the tool enters the pre-drilled hole effortlessly and ensures the thread starts perfectly straight and aligned. It distributes the cutting force across many teeth, making it very easy to turn. Limitation: It will not cut full, usable threads near the bottom of a hole because the tip is tapered down. 2. Plug Tap (Intermediate / Second Tap) The Plug Tap is the most versatile and frequently used style of the three. The Tip Chamfer: It features a moderate taper spanning 3 to 5 threads at the tip. The Purpose: In open through-holes, a plug tap can often be used all by itself to cut the entire thread in one pass. In a blind hole, it is used second—following the Taper Tap—to cut the threads much deeper toward the floor. Limitation: Like the taper, it still leaves the bottom 3 to 5 threads incomplete. 3. Bottoming Tap (Finisher Tap) The Bottoming Tap is used exclusively to finish a blind hole. The Tip Chamfer: It features a very short, aggressive taper of only 1 to 2 threads at the tip. The Purpose: It is used as the final step after the hole has already been pre-threaded by the Taper and Plug taps. It allows you to cut full, functional threads all the way down to the very floor of a dead-end hole. Limitation: Never try to start a fresh thread with a bottoming tap. Because it has almost no alignment lead-in, it takes immense force to turn, is highly likely to start crooked, and will easily snap.