Cylinder head

When it comes to cars, the cylinder head is cast from aluminium alloys. The configuration and features for machining vary according to the engine fuel. The cylinder head is fitted on the cylinder crankcase and is responsible for the fuel and fresh air supply. Due to its stringent requirements for quality and tolerance, it is the most demanding component for machining in engine manufacture. Through precise valve control and minimal friction losses in the camshaft bearings, fuel consumption and emissions are already reduced before the combustion process.
„Cylinder head with valve train, injector bores and camshaft bearing bores structure

Key features

  1. Valve Train
  2. Injector bore
  3. Camshaft bearing bore
  4. Core plug bore

  • The tool carries out the pre-machining of the base bore in the internal combustion engine.

    1. Pre-machining – blind bore

    High feeds and large chip quantities require sturdy, PCD-tipped boring tools with efficient chip removal. Machining forms the foundation for all subsequent process steps in the valve train.

  • The tool carries out the finishing of the blind bore in the internal combustion engine

    2. Finishing – blind bore

    Multi-blade, PCD-tipped boring tools ensure dimensional accuracy and surface quality. In this machining step, precision is crucial so that the valve seat rings and valve guides can be pressed in later.

  • “The tool carries out the pre-machining of the valve seat in the internal combustion engine.”

    3. Pre-machining – valve seat and valve guide

    Once the valve seat ring and valve guide are pressed in, machining of the hard workpiece materials takes place. Extremely tight tolerances and wear-resistant cutting materials are required.

  • The tool carries out the finishing of the valve seat in the internal combustion engine.

    4. Finishing – valve seat and valve guide

    Fine boring or reaming tools are used for precise sealing surfaces. These ensure high process reliability and long tool lives.

1. Valve train

PROCESS CONDITIONS
  • High-precision requirements for form and position tolerance
  • Cylindricity 10 μm 
  • Diameter tolerance 15 μm
  • Coaxiality from valve seat to valve guide
  • Circularities < 8 μm
  • Angle tolerances on the valve seat ring in the μm range
  • Materials with high resistance to wear on valve seat ring
  • Maximum process reliability and accuracy of repetition
PCD fine‑boring tools for machining the valve train pilot bore in the cylinder head

Blind Bore

1. Pre-machining
PCD boring tool

  • Short and stable tool design for maximum positional accuracy.

2. Finishing
PCD boring tool
 
  • Multi-blade tool concept for short processing times.

Werkzeuge zur Bearbeitung vom Zylinderkopf: Ventilsitz und Ventilführung

Valve Seat / Valve Guide

3. Pre-machining
Pilot tool

  • Short, stable tool ensures maximum positional accuracy for the subsequent finishing tool.

4. Finishing
Finishing tool

  • High-precision fine machining with adjustable fine boring tool with EA system and quick-change valve guide reamer.

2. Injector bore

PROCESS CONDITIONS
  • Very large step changes > 10 mm
  • Critical chip removal due to component contour
  • Fluctuating casting situations
  • Surface requirements of up to Rz 4
  • Diameter tolerances in H7 range
  • Wide range of contour designs with multiple tight-tolerance
  • radii and chamfers (± 0.1 mm)
Three tools for machining the cylinder head via the injector bore using a three‑stage process

3-step process for maximum process reliability

1. Pre-machining
PCD multi-stage solid drill
 
  • Multi-blade solid drill and boring tool with brazed PCD inserts and special chip flutes for optimal chip removal.


2. Semi-finishing
Solid carbide step drill

  • Special cutting-edge geometry and spiralisation for the best chip breaking and chip removal.


3. Finishing
PCD step reamer

  • Multi-blade step reamer with brazed PCD inserts, special cutting-edge geometry and expanded chip flutes for optimal chip removal.

Two tools for machining the cylinder head via the injector bore using a two‑stage process

Two-step process for maximum productivity

1. Pre-machining
PCD boring tool with solid carbide drill

  • Maximum usable tool life of PCD inserts due to Drilling from solid stage that can be changed separately.

2. Finishing
PCD step reamer

  • Multi-blade step reamer with brazed PCD inserts and expanded, polished chip flutes for optimal chip removal.

3. Camshaft bearing bore

PROCESS CONDITIONS
  • Cylindricity (15 μm over 100 mm)
  • Circularity < 5 μm
  • Diameter tolerances of 15 – 20 μm
  • Surface qualities of < Rz 5 μm
  • Repeated cutting due to the interrupted cut
  • Tools with very high length–diameter ratio
Large tool, also known as a line boring bar

Maximum productivity with one-shot solution

1. Pre- and finishing machining
Line boring bar
 
  • One-shot machining with very good straightness of the bore due to additional bearings with roller or plain bearings.

Two fine boring tools for machining the internal combustion engine

Ultimate process reliability with 2-step process

1. Pre-machining
Fine boring tool

  • Guided fine boring tool with easy-to-adjust HX indexable inserts.

2. Finishing
Fine boring tool

  • Guided fine boring tool with indexable inserts – with simple blade configuration and additional pre-cutting stage for maximum quality requirements.

4. Core plug bore

PROCESS CONDITIONS
  • Surface quality Ra < 16 μm
  • Circularity 0.05 mm
  • Diameter tolerance H7
  • Positional accuracy
Tool for machining the core plug bore on an internal combustion engine

Core plug bore

1. Semi-finishing
PCD step boring tool

  • Short, compact tool design for maximum tool stability.