Widia Gtd
Widia Gtd VTSFT-TC5130 Spiral Flute Tap #4-40 Bottoming 2 Flutes UNJC
Spiral flute tap cuts #4-40 UNC threads with a 33/64 inch thread length in a 1 7/8 inch overall length
- #4-40 UNC thread cuts precise internal threads
- Spiral flute design clears chips efficiently in blind holes
- Bottoming chamfer reaches full depth in through or blind holes
- High-speed steel with black oxide resists wear during repeated use
- Two flutes balance strength and chip evacuation for reliable tapping
Spiral Flute Tap #4-40 UNJC
The Widia Gtd VTSFT-TC5130 is a high-speed steel spiral flute tap designed for cutting internal UNJC threads in a #4-40 size. It features a bottoming chamfer and two flutes for efficient chip evacuation in blind holes. The tap has a black oxide finish and a right-hand thread direction. It is intended for machinists and maintenance professionals producing Class 3B fit threads.
Practical limits of UNJC threading
The UNJC thread form requires a controlled root radius that increases minor diameter compared to standard UNC threads, limiting the maximum thread depth achievable in a single pass. A 75 percent thread engagement calls for a 2.20 mm drill size to prepare the hole correctly. The H2 thread limit and 3B class of fit provide a tight tolerance band that leaves little room for drill wander or material springback. Bottoming taps like this one need adequate clearance at the hole bottom to avoid bottoming out the flutes.
Upgrade from standard UNC taps
This tap replaces general-purpose UNC taps when the application demands the stronger root profile and tighter tolerance of the UNJC aerospace standard. The jump is worth it when drawings specify UNJC Class 3B threads or when fatigue resistance in high-stress fastener joints is a design requirement. It is not for through-hole threading where a plug or taper chamfer would start the thread more easily, nor for materials that demand coated or carbide tooling for tool life.
Highlights
- #4-40 UNC thread cuts precise internal threads
- Spiral flute design clears chips efficiently in blind holes
- Bottoming chamfer reaches full depth in through or blind holes
- High-speed steel with black oxide resists wear during repeated use
- Two flutes balance strength and chip evacuation for reliable tapping
Specifications
| Brand | WIDIA |
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Questions about this item
Should I choose the #4-40 UNJC tap or a different thread size?
Select the #4-40 UNJC tap only when the hole and fastener match that exact thread size and class of fit 3B; other sizes will not produce the correct thread form.
What does the 33/64 inch thread length mean when I am tapping a hole?
It indicates the cutting portion of the tap extends 33/64 inch, so the hole must be at least that deep plus clearance for the bottoming chamfer to form full threads.
How does the H2 thread limit affect the threads I cut?
The H2 limit sets the pitch diameter tolerance for a 3B class of fit, producing a tighter, more precise internal thread than looser limits.
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