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Hand Threader M20X1.25 DIN 2181/2 HSS
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  • Hand Threader M20X1.25 DIN 2181/2 HSS
  • Hand Threader M20X1.25 DIN 2181/2 HSS - nr. 1
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Hand Tap M20X1.25 DIN 2181/2 HSS

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Description

Technical data for the M20x1.25 hand tap

Technical data
Nominal diameter d1 mm M20
Thread pitch P mm 1.25 mm
Overall length l1 80 mm
Flute length l2 22 mm
Shank diameter d2 16 mm
Square drive size a 12 mm
Tap drill diameter 18.8 mm
Thread angle G 60°
Tap tolerance ISO2 6H
Fine-thread taps drawing

Roughing tap and finishing tap – how much material each removes

Division of work in the 1–2 set

The M20x1.25 thread is cut into the wall of a hole with a diameter of 18.8 mm. The thread groove extends 0.6 mm into the wall. A single tap would have to cut the entire groove at once, requiring substantial hand torque and risking breakage. The set divides this work into two passes.

Tapping an M20x1.25 hole: 18.8 mm hole, taps No. 1 and No. 2 in a cross section of the plate
Tapping an M20x1.25 hole: 18.8 mm hole, taps No. 1 and No. 2 in a cross section of the plate

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.

TapChamferChamfer angleMaterial removedHow it works in the hole
No. 1 – roughing taplong, 8 threads5°the main portion of the grooveenters smoothly and establishes thread alignment
No. 2 – finishing tapshort, 2 threads20°the remainder, to the full profilefollows 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 M20x1.25 hole – sequence 1, 2

Hand tapping step by step

Thread M20x1.25 in four steps

ØDrilling

Drill bit 18.8 mm

1Roughing tap

Chamfer 8 threads

2Finishing tap

Chamfer 2 threads

✓Finished thread

Tolerance 6H

Turning sequence: half a turn clockwise, a quarter turn counterclockwise | Between taps: remove chips from the hole

Start with the hole. The drill diameter is easy to calculate: thread diameter 20 mm minus pitch 1.25 mm gives 18.75 mm — in practice, use a 18.8 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 50 mm, or 2.5 times the thread diameter (2.5 x 20 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.

M20x1.25 thread in a through hole and a blind hole – cross sections with clearance for chips and the 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 – the finishing tap produces the full profile

Back out the roughing tap and remove chips from the hole. Screw the finishing tap into the cut threads by hand – it should engage them on its own. Continue turning at the same rhythm as with the roughing tap. The finishing tap removes the remaining material and cuts the groove to the full profile within tolerance 6H. When it screws in smoothly all the way, the thread is complete – check it with an M20x1.25 screw.

M20x1.25 fine-thread hand taps

Hand Tap M20x1.25 DIN 2181/2 HSS is designed to produce precise metric fine threads in structural steels, tool steels, and nonferrous alloys. Its robust construction from high-quality high-speed steel ensures a clean profile, dimensional repeatability, and long service life in workshop and production applications.

Technical data: nominal diameter twenty millimeters, pitch 1.25 mm, sixty° profile according to ISO 68-1, internal thread tolerance class 6H according to ISO 965, right-hand. Straight flutes ensure smooth chip evacuation, reducing the risk of jamming. Ground high-speed steel (HSS) ensures high resistance to microchipping and retention of a sharp cutting edge. The two-tap design according to DIN 2181/2 — starter (I) and finisher (II) — balances torsional loads and provides axial guidance. In production practice, high operational precision and consistent results are supported by M20x1.25 Hand Tap Set.

  • Precise guidance — the two-stage operating sequence reduces vibration and maintains axial alignment during tapping.
  • High durability — fine-grained HSS ensures longer cutting edge life and stable cutting parameters.
  • Dimensional repeatability — tolerance class 6H ensures an accurate fit with 6g external threads.
  • Organized operation — M20x1.25 Hand Tap Set enables a logical sequence of passes, improving machining control and efficiency.

Compliance with DIN 2181/2 (construction), ISO 68-1 (thread profile), and ISO 965 (class 6H) ensures full compatibility with inspection instruments and predictable results in workshop and assembly operations.

Stages of cutting an M20x1.25 thread with a 2-piece set: roughing tap and finishing tap


Roughing tap and finishing tap profiles

Frequently asked questions

The set consists of two taps — a roughing tap and a finishing tap, which guarantee a fully formed thread when used in sequence.

The HSS tool works well in low-carbon steel, aluminum, brass, and other materials with good machinability.

Yes, the set can be used in both through holes and blind holes, in accordance with DIN 2181 and class 6H.

Product accessories

Tap wrench No. 4

Reference: 3891 In stock > 10 items

€14.47

€17.80 brutto

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Hand Tap M20X1.25 DIN 2181/2 HSS

Hand Tap M20X1.25 DIN 2181/2 HSS

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