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Flat Honing and Lapping with Two-Wheel Machines

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Flathoning – “Clean Lapping”

The required specification for lapping and polishing machine manufactures is shorter machining times achieved in a ecologically friendly environment. New work-pieces and/or new materials are constantly being developed for use with new applications.


Flathoning uses the principle of planetary kinematics. In french, we call this working process “la rectirodologie” (rectifier = grinding, roder = lapping). Fine grinding is another term that largely corresponds to this working process. Our slogan “clean lapping” refers to the highest possible level of quality combined with clean methods.


At relatively low cutting speeds (compared to grinding), flathoning offers the benefit of comprehensive tool application instead of linear contact as in grinding. The work is carried out at a low specific pressure, unlike in grinding where the specific pressure is quite high and can cause burned areas. Corundum, silicon, CBN, or diamond working wheels (bound) in various grain sizes and binding are used for the cutting process, instead of the process with a loose grain. Thin honing oil or water and a small quantity of generally biologically degradable additives are used as the coolant. The coolant is cleaned continuously by a filter system in a closed circuit. In order to understand the procedure between the work pieces and a working wheel better, it is with studying various research papers and the easy – to – understand reprint “Lapping Technology” by A.W. Stahli. The latter work focus particularly on practical elements.


The main advantages of the flathoning technique are its excellent geometrical results, which correspond to lapping quality and can be adopted for most materials. Customized tolerances fall in the range of 1 micron depending on the work piece shape, 0.3-0.6 micron for flatness, 0.5-1 microns for parallelism and up to Ra 0.025 microns for the surface quality, depending on the material. The prerequisite for such results is the right choice of working tools.


This innovative machining technique produces clean and glossy surfaces. It so permits easy cleaning of the work pieces, as only a gentle rinse is necessary. This is crucially important both for production and for checks.

Advantages of this technique

The stock removal is far greater than with conventional lapping. The “cut-up” material surface (drawn grain) produces glossy surfaces and shorter machining times. Operations such as cutting and grinding can be omitted. Other major advantages are that virtually all materials can be machined, and the removal rates lie between 0.01-1 mm per minute, depending on the material, the surface size and the required surface quality. In certain working processes, this technology also permits the elimination of one or more work phases, which helps to reduce the machining costs dramatically.

The company Stahli Lapping Technology Ltd has developed the relevant flathoning technology from its knowledge of two-wheel lapping and has integrated all the necessary machining parameters into its DLM series (figures 10, 11, 17).Options with semi and full automation have also been developed and have proved their value in widespread production.


The various refinishing centers the A.W. Stahli AG are working constantly to guarantee continuous enhancements with the specifically required equipment in each case. This ensures progress for a wide variety of requirements and customer wishes in the field of high-precision machining. Finally, we can sum up by saying that the described new technology of flathoning or fine grinding provides an extremely economical working process in the high precision machining sector. It also satisfies the constantly increasing and justified requirements of environmental protection.