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Description
Material HSS
Thread size M30 left
Number of pieces3 pcs
Tolerance 6H ISO2
Technical data for the M30 left-hand hand tap
| Technical data | |
|---|---|
| Thread Diameter d1 | M30 |
| Thread Pitch P | 3.5 mm |
| Overall Length l1 | 135 mm |
| Flute Length l2 | 50 mm |
| Shank Diameter d2 | 20 mm |
| Square Drive Width Across Flats a | 16 mm |
| Tap Drill Hole | 26.5 mm |
Roughing, intermediate, and finishing taps – how much material each removes
Division of work in the 1–2–3 set
The M30 x3.5 LH thread is formed in the wall of a hole with a diameter of 26.5 mm. The thread groove extends 1.75 mm into the wall. A single tap would have to cut the entire groove at once – by hand, this creates 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 6H 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. Keep the set together and always start with the roughing tap.
How to tap an M30 LH hole – sequence 1, 2, 3
Hand tapping step by step
Thread M30 x3.5 LH in five steps
ØDrilling
Drill bit 26.5 mm
1Roughing tap
Removes approx. 60%
2Intermediate
Removes approx. 30%
3Finishing tap
Removes approx. 10%
✓Finished thread
Tolerance 6H
Turning sequence: half a turn counterclockwise, a quarter turn clockwise | Between taps: remove chips from the hole
Start with the hole. The drill diameter is easy to calculate: thread diameter 30 mm minus pitch 3.5 mm gives 26.5 mm. An undersized hole is a common cause of a tap 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 45 mm, or 1.5 times the thread diameter (1.5 x 30 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 into a tap wrench and position it perpendicular to the surface. Check the angle from two sides, for example with a square. This is a left-hand thread, so turn in the opposite direction to usual: half a turn counterclockwise, then a quarter turn clockwise. 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
Unscrew the roughing tap and remove chips from the hole. Screw the intermediate tap by hand into the previously cut threads – 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 smoothly all the way in, the thread is ready – check it with an M30 LH screw.
M30 left-hand HSS hand tap DIN 2181 – 3-piece set for large left-hand threads
The M30 left-hand hand tap set is a professional set of three tools for cutting left-hand internal threads with a diameter of 30 mm and a pitch of 3.5 mm. M30 left-hand HSS hand taps conforming to DIN 2181 are used in rotary drives, spindles, and industrial machinery, where a standard right-hand thread could loosen on its own during equipment operation.
Key benefits of the M30 left-hand tap set
- 3-piece set (roughing, intermediate, and finishing taps) – three-stage cutting distributes the load when tapping a large diameter
- M30 left-hand thread – prevents joints in rotating components and spindles from loosening
- HSS high-speed steel – enables machining of structural and alloy steels with tensile strengths up to 800 MPa
- Tolerance 6H according to DIN 2181 – a standard for left-hand metric threads ensuring a precise fit
- Large industrial diameter – for joints transmitting substantial loads in drive mechanisms
The M30 left-hand hand tap set is suitable for machine manufacturing plants, rotary equipment service shops, and industrial drive companies. Use a drill bit with a diameter of 26.5 mm to drill the tap hole for an M30 left-hand thread. Remember the direction of rotation – a left-hand tap turns counterclockwise.
Tolerance 6H — metric thread tolerance classes
| Class | Accuracy | Application | Status |
|---|---|---|---|
| 4H / 4g | High | Precision connections, hydraulics | — |
| 6H / 6g | Standard | Machine building, general-purpose | SELECTED |
| 7H / 8g | Low | Large clearance, easy assembly | — |
6H = internal thread (nut, hole) | 6g = external thread (screw)
Frequently asked questions
A 26.5 mm drill bit is used for an M30 thread with a pitch of 3.5 mm. The hole diameter is identical for right-hand and left-hand threads.
M30 left-hand threads are used in machine spindles, rotary drives, and components where a right-hand thread could loosen.
DIN 2181 is the standard for left-hand taps, while DIN 352 covers right-hand taps. The profiles and dimensions are identical; the thread direction differs.
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