Hand Tap Finisher DIN 352 HSS-G left hand thread - M 42 x 4.5 LH

• for general use
• machinable materials up to 900 N/mm²
• unalloyed and low-alloyed steel
• for through and blind holes
• for manual use

1. Drill core hole: Drill the core hole with the appropriate drill bit for the M 42 thread (approx. Ø 37.5 mm with a 4.5 pitch).
2. Thread preparation: First, use a taper tap (Ring 1) and then an intermediate tap (Ring 2) from a suitable hand tap set to pre-form the thread.
3. Insert finisher: Securely clamp the finisher (this tool, often unmarked) in a tap wrench.
4. Lubrication: Apply plenty of cutting oil to the tap and the pre-formed thread to reduce friction and ensure a clean cut.
5. Finish cutting the thread: Position the finisher straight and slowly turn it in the left-hand thread direction (counter-clockwise). Pay attention to even pressure and avoid tilting.
6. Completion and cleaning: When the thread has reached the desired depth, carefully turn the finisher back. Thoroughly clean the cut thread and the tap of chips and residues.

• Thread Type: metric ISO thread DIN 13
• Standard: DIN 352
• Material: HSS-G
• Tolerance: ISO 2 / 6H
• Nominal Size: M 42 x 4.5
• Overall Length (L1): 150 mm
• Thread Length (L2): 63 mm
• Shank Diameter (D2): 32 mm
• Drive Square: 24 mm
• Article Number: 27086-3

Q1: What is a left-hand thread and what is it used for?

A1: A left-hand thread is tightened counter-clockwise and loosened clockwise. It is used in applications where a right-hand thread would unintentionally loosen due to rotation or vibrations. A well-known example is the left pedal on bicycles to prevent loosening while pedaling. For more information on left-hand threads, see this video: Left Hand Threads.

Q2: Why is a 3-piece set often required for hand taps?

A2: For manual use, a thread is typically cut in three steps: with a taper tap, an intermediate tap, and a finishing tap. This distributes the cutting load, simplifies the threading process, and protects the tools, especially for larger or deep threads. The finishing tap brings the thread to its exact final dimension and the desired profile accuracy.

Q3: What does the material designation HSS-G mean?

A3: HSS-G stands for "High Speed Steel - Ground." This material is ideal for machining well-machinable materials and offers good hardness and wear resistance for general use. The ground finish ensures precise cutting edges and a good surface quality.

Q4: For which materials is this tap suitable?

A4: This hand tap is suitable for machinable materials up to a strength of 900 N/mm². This includes unalloyed and low-alloyed steels, which are common in mechanical engineering and general metalworking.

Q5: Can this finisher be used alone without a taper and intermediate tap?

A5: Technically yes, but it is strongly recommended to use the taper and intermediate taps first. The finisher is designed to bring an already pre-formed thread to its final dimension and would be overloaded when used in a plain hole, which can lead to tool breakage or a messy thread.

Q6: What is the difference between a through and a blind hole?

A6: A through hole is a bore that goes all the way through the workpiece, so the thread is visible from both sides. A blind hole is a bore that does not go completely through the workpiece, leaving the thread with a closed bottom. This finisher is suitable for both types of holes.

Q7: Why is the ISO 2 / 6H tolerance important?

A7: The ISO 2 / 6H tolerance class is the standard tolerance for metric ISO threads. It ensures that the cut thread is precise enough to allow for a correct fit with the corresponding screws. This is crucial for the functionality and longevity of the connection.