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Description
Material HSS
Thread size M7 left
Number of pieces3 pcs
Tolerance 6H ISO2
Technical data for the M7 left-hand hand tap
| Technical data | |
|---|---|
| Thread Diameter d1 | M7 |
| Thread Pitch P | 1 mm |
| Overall Length l1 | 56 mm |
| Flute Length l2 | 18 mm |
| Shank Diameter d2 | 6 mm |
| Square Drive Width Across Flats a | 4.9 mm |
| Tap Drill Hole | 6.0 mm |
Roughing, intermediate, and finishing taps – how much material each removes
Division of work in the 1–2–3 set
The M7 x1 LH thread is formed in the wall of a hole with a diameter of 6 mm. The thread groove extends 0.5 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. 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 an M7 LH hole – sequence 1, 2, 3
Hand tapping step by step
Thread M7 x1 LH in five steps
ØDrilling
Drill bit 6 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 7 mm minus pitch 1 mm gives 6 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 10.5 mm, or 1.5 times the thread diameter (1.5 x 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 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 M7 LH screw.
M7 left-hand HSS hand tap DIN 352 – 3-piece set for nonstandard left-hand threads
The M7 left-hand hand tap set is a specialized set of three tools for cutting left-hand internal threads with a diameter of 7 mm and a pitch of 1 mm. M7 left-hand HSS hand taps conforming to DIN 352 combine a nonstandard diameter with a left-hand thread direction, making them essential for specific automotive, aerospace, and machinery applications where protection against self-loosening is required.
Key benefits of the M7 left-hand tap set
- 3-piece set (roughing, intermediate, and finishing taps) – three-stage cutting ensures high thread quality
- M7 left-hand thread – protects joints in rotating components against loosening
- Nonstandard diameter of 7 mm – fills the gap between M6 and M8 in specialized applications
- HSS high-speed steel – enables machining of structural steels and aluminum up to 800 MPa
- Tolerance 6H according to DIN 352 – a precise fit with M7 left-hand screws of tolerance class 6g
The M7 left-hand hand tap set is suitable for automotive workshops, aerospace plants, and specialized machinery service shops. Use a drill bit with a diameter of 6 mm to drill the tap hole for an M7 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 6 mm drill bit is used for an M7 thread with a pitch of 1 mm. The hole diameter is identical for right-hand and left-hand threads.
M7 left-hand threads are used in specialized machinery, rotating components, and aerospace structures requiring protection against loosening.
M7 left-hand screws are specialized products. Available from fastener suppliers for the aerospace and machinery industries.
Product accessories
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Shipping
All orders are delivered by courier company GLS. For orders exceeding 369 PLN gross shipping is FREE
| Courier GLS | Przelew24 / Prepayment | 14,76 zł gross | Delivery time 1 working day |
| Courier GLS | Cash on delivery | 17,26 zł gross | Lead time 1 working day |
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