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Description
Technical data for the UNC 1/2-13 hand tap
| Technical data | ||
|---|---|---|
| Nominal Diameter d1 Inches/mm/Decimal | UNC 1/2-13 | |
| Thread Pitch P in Inches and mm | 13 threads per inch | 1.95 mm |
| Thread Diameter d1 mm / Decimal | 12.70 mm / 0.5000 in | |
| Thread angle G | 60° | |
| Thread Standard | UNC ANSI B-1.1 | |
| Overall Length l1 | 80 mm | |
| Flute Length l2 | 25 mm | |
| Shank Diameter d2 | 9 mm | |
| Square Drive Width Across Flats a | 7 mm | |
| Tap Drill Hole | 10.8 mm | |
Roughing, intermediate, and finishing taps – how much material each removes
Division of work in the 1–2–3 set
The UNC 1/2-13 thread is cut into the wall of a 10.8 mm diameter hole. The thread groove extends 0.95 mm into the wall. A single tap would have to cut the entire groove at once – by hand, this means high resistance and a risk of breakage. The set divides this work into three layers.
The drawing shows the entire set in operation. All three taps have the same shank and the same length. They differ in chamfer length: No. 1 has a taper spanning 7–10 threads, while No. 3 spans only 1–2 threads. The detail views at the hole wall show how the thread groove deepens after each tap.
| Tap | Chamfer | Material removed | How it works in the hole |
|---|---|---|---|
| No. 1 – roughing tap | long, 7–10 threads | approx. 60% | enters smoothly and establishes thread alignment |
| No. 2 – intermediate | medium, 3–5 threads | approx. 30% | screws into the previously cut threads and starts cutting only deeper in the hole |
| No. 3 – finishing tap | short, 1–2 threads | approx. 10% + sizing | turns easily and produces the full 2B profile |
How to identify the tap numbers in the set
The chamfer is the tapered end of the tap. No. 1 has the longest chamfer and No. 3 the shortest – the difference is immediately visible when they are placed side by side. No. 1 and No. 2 have shallower thread profiles; only No. 3 has the full profile. The number can also be identified on the shank: No. 1 has one ring, No. 2 has two, and No. 3 has none. Keep the set together and always start with the roughing tap.
How to tap a UNC 1/2-13 hole – sequence 1, 2, 3
Hand tapping step by step
Thread UNC 1/2-13 in five steps
ØDrilling
Drill bit 10.8 mm
1Roughing tap
Removes approx. 60%
2Intermediate
Removes approx. 30%
3Finishing tap
Removes approx. 10%
✓Finished thread
Tolerance 2B
Turning sequence: half a turn clockwise, a quarter turn counterclockwise | Between taps: remove chips from the hole
Start with the hole. For inch threads, pitch is specified in threads per inch, so first convert it to millimeters: an inch equals 25.4 mm, and 25.4 : 13 threads ≈ 1.95 mm. The diameter of the UNC 1/2-13 thread is 1/2 inch, or 12.7 mm. The diameter of 12.7 mm minus the pitch of 1.95 mm gives 10.75 mm – in practice, use a 10.8 mm drill bit. An undersized hole is a common cause of taps twisting off in the workpiece.
Through hole or blind hole – how deep to drill
The set taps both types of holes. In a through hole, the thread extends through the full material thickness. In a blind hole, cut the thread to 19.1 mm, or 1.5 times the thread diameter (1.5 x 12.7 mm, shown as 1.5D in the drawing). Drill the hole deeper than the thread. The clearance below the thread accommodates chips and the finishing tap chamfer.
No. 1 – the roughing tap establishes thread alignment
Fit the roughing tap in the tap wrench and position it perpendicular to the surface. Check the angle from two sides, for example with a square. Turn half a turn clockwise, then a quarter turn counterclockwise. Reversing breaks the chip into short pieces – a slight crunch is normal. The first threads determine whether the thread will be straight.
No. 2 and No. 3 – deepening and full profile
Back out the roughing tap and remove the chips from the hole. Screw the intermediate tap into the cut threads by hand – it should engage them naturally. It turns easily at first and starts cutting only deeper in the hole. The finishing tap enters with almost no resistance and cuts the final portion of the profile only at the end. When it screws in smoothly all the way, the thread is complete – check it with a UNC 1/2-13 screw.
UNC 1/2-13 hand tap – set of 3 taps for the most popular American threads
UNC 1/2-13 hand tap is a three-piece tool set for producing internal Unified National Coarse – UNC threads (American unified coarse threads). The set consists of HSS roughing, intermediate, and finishing taps and complies with DIN 352.
UNC 1/2-13 tap features
- Class 2B tolerance – general-purpose accuracy ensuring a proper fit
- The most popular diameter: 1/2 inch (12.70 mm) – the most common size in American industry
- 13 threads per inch (1.95 mm pitch) – coarse thread profile allowing quick assembly and disassembly
- Three-stage tapping – cutting load distributed among roughing, intermediate, and finishing taps
- HSS high-speed steel – effective machining of steel, aluminum, and cast iron up to 800 MPa
The UNC 1/2-13 thread is a staple in American automotive applications, agricultural machinery, and construction equipment. The UNC 1/2-13 inch tap is essential in every workshop servicing Ford, Chevrolet, and Dodge vehicles, as well as John Deere and Caterpillar machines.
Frequently asked questions
Calculate the hole diameter using the formula: d = D - P. For UNC 1/2-13: d = 12.70 mm - 1.95 mm = 10.75 mm. Use a 10.8 mm or 11 mm drill bit for proper tapping.
UNC 1/2-13 is found virtually everywhere in American equipment – cars (Ford, GM, Chrysler), agricultural tractors, excavators, forklifts, as well as structural bolts and fasteners. It is the most versatile inch size.
You need a caliper and a thread pitch gauge. External thread (on a shaft): measure the outside diameter; it should be 12.70 mm (1/2 in). Internal thread (in a hole): measure the hole diameter; it should be approximately 10.8 mm. Then place the thread pitch gauge against the threads; the 13 TPI leaf fits this thread. The 60° thread angle confirms the American standard.
Product accessories
Tapered countersink 16.5/90 DIN 335 B HSS
Reference: 0000006120 In stock > 10 items
€23.68
€29.13 brutto
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