UNIFIED NATIONAL COURSE UNC TAPS
MAJOR DIAMETER:#8 X 32
TAP TYPE:TAPER
Quantity:
Pickup available at Hurrell Way Store
Usually ready in 4 hours
UNIFIED NATIONAL COURSE UNC TAPS
#8 X 32 / TAPER
Hurrell Way Store
Pickup available, usually ready in 4 hours
38A Hurrell Way
Rockingham WA 6168
Australia
SRB - 24/7 Fittings
Pickup currently unavailable
38A Hurrell Way
Rockingham WA 6168
Australia
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).
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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.