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Hand Tap M12X1.25 LH DIN 2181/2 HSS
5665
Thread size: M12x1,2542 sizes of this tap
€17.80 tax inc.
Net price: €14.47
Description
Technical data for the M12x1.25 left-hand hand tap
| Technical data | |
|---|---|
| Nominal diameter d1 mm | M12 |
| Thread pitch P mm | 1.25 mm |
| Overall length l1 | 87 mm |
| Flute length l2 | 24 mm |
| Shank diameter d2 | 9 mm |
| Square drive size a | 7.1 mm |
| Tap drill diameter | 10.8 mm |
| Thread angle G | 60° |
| Tap tolerance | ISO2 6H |
Roughing tap and finishing tap – how much material each removes
Division of work in the 1–2 set
The M12x1.25 LH thread is cut into the wall of a hole with a diameter of 10.8 mm. The thread groove extends 0.6 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 two passes.
The drawing shows the entire set in operation. Both taps have the same shank and the same length. They differ in their chamfer, the tapered tip: No. 1 has a chamfer spanning 8 threads, while No. 2 spans only 2 threads. The detail windows at the hole wall show how the thread groove deepens after each tap.
| Tap | Chamfer | Chamfer angle | Material removed | How it works in the hole |
|---|---|---|---|---|
| No. 1 – roughing tap | long, 8 threads | 5° | the main portion of the groove | enters smoothly and establishes thread alignment |
| No. 2 – finishing tap | short, 2 threads | 20° | the remainder, to the full profile | follows the cut threads and produces the full 6H profile |
How to distinguish the taps in the set
The chamfer on No. 1 is 4 times as long as the chamfer on No. 2 — the difference is immediately visible when you place them side by side. No. 1 has an incomplete thread profile; only No. 2 has the full profile. The number is also indicated on the shank: No. 1 has one ring, No. 2 has none. Keep the set together and always start with the roughing tap.
How to tap an M12x1.25 LH hole – sequence 1, 2
Hand tapping step by step
Thread M12x1.25 LH in four steps
ØDrilling
Drill bit 10.8 mm
1Roughing tap
Chamfer 8 threads
2Finishing tap
Chamfer 2 threads
✓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 12 mm minus pitch 1.25 mm gives 10.75 mm — in practice, use a 10.8 mm drill bit. 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 30 mm, or 2.5 times the thread diameter (2.5 x 12 mm, shown as 2.5D in the drawing). Drill the hole deeper than the thread. The finishing tap has a chamfer spanning 2 threads, so approx. 2 incomplete threads remain near the bottom. The extra depth below the thread accommodates them along with the chips.
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 – the finishing tap produces the full profile
Unscrew the roughing tap and remove chips from the hole. Screw the finishing tap by hand into the cut threads — it should engage them naturally. Continue with the same turning sequence as for the roughing tap. The finishing tap removes the remaining material and cuts the groove to its full profile within 6H tolerance. Once it screws smoothly all the way in, the thread is complete — check it with an M12x1.25 LH screw.
M12x1.25 left-hand fine-thread hand taps
M12x1.25 left-hand hand taps DIN 2181 HSS are designed to cut left-hand metric fine threads with a pitch of 1.25 mm. The M12x1.25 left-hand tap set consists of two parts – a roughing tap and a finishing tap – which, when used in sequence, allow a clean thread profile to be formed accurately in stages.
The M12x1.25 left-hand hand tap set is made of high-speed steel (HSS), providing high durability and wear resistance. M12x1.25 left-hand hand taps are used for machining low-carbon steel, aluminum alloys, brass, and other materials with good machinability. Left-hand threads are used in joints requiring opposite tightening directions, preventing components from loosening on their own.
The M12x1.25 left-hand hand tap set meets the requirements of DIN 2181, and the finished thread conforms to tolerance class 6H (ISO 2). It is suitable for use in through holes and blind holes. A tap wrench attached to the square drive is used for operation, providing stable tool guidance and precise process control.
Key features:
- M12x1.25 left-hand tap set– the set includes a roughing tap and a finishing tap.
- Left-hand thread – used in joints requiring opposite tightening directions.
- HSS high-speed steel – long service life and abrasion resistance.
- Versatile applications – for through holes and blind holes.
Stages of cutting an M12x1.25 left-hand thread with a 2-piece set: roughing tap and finishing tap
Frequently asked questions
LH means a left-hand thread, cut in the opposite direction to a standard right-hand thread.
The set contains two taps — a first roughing tap for initial guidance and a second finishing tap for the final thread profile.
Yes, M12x1.25 left-hand hand taps are suitable for both through holes and blind holes.
M12x1.25 left-hand HSS taps work well in low-carbon steel, aluminum, brass, and other easy-to-machine materials.
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