Many who roll tap threads under minimum quantity lubrication know the situation: the thread is true to gauge - but component and tool are dirty and must be cleaned.
The reason can be found in the furrows of the grooved thread. Although the material flows during thread forming, small material particles are loosened in the tips of the furrow during machining. These collect in the groove of the roll tap - and from there contaminate the entire tool and finally also the workpiece.
This contamination takes its toll. Additional, abrasive wear caused by the material particles clog the thread part of the tool and cause its service life to collapse. The necessary component cleaning after machining also takes up valuable process time.
BASS has carried out extensive tests and test series in order to control contamination. The solution can be found in the internationally patented multi-groove. Due to the special geometry of this new groove shape, the tool already gets rid of the particles during machining. These are picked up by the large-volume multi-groove. The special shape of the multi-groove increases the cleansing effect of the cooling medium, allowing the unwanted material particles to be removed from the grooves and thus from the tool and component. The taps come "clean" from the machining process.
But especially the service life of the threading tool benefits from the multi-groove. Compared to the conventional groove form, the tool life increases by up to 30%. The air contained in the blind hole of the conventional straight groove can only escape with a delay during thread forming. It is compressed against the hole bottom, the cooling lubricant presses against a "wall" of air. Due to this "counterpressure", the coolant does not wet the machining area sufficiently and cannot perceive its lubricating effect. This is particularly important when using minimum quantity lubrication (MQL). If the pressure at which the aerosol is supplied is only slightly higher than the pressure in the blind hole, sufficient wetting of the bore wall is not ensured. As a result, friction increases dramatically and the service life of the threading tool collapses.
Due to the special geometry and the increased volume of the multi-groove, the enclosed air can escape more quickly. The bore surface is better wetted. As a result, the tool life of the threading tool increases by up to 30%. Process reliability also increases significantly. The logical conclusion: the deeper the blind hole, the greater the amount of air that has to escape - and thus the greater the effect of the multi-groove.
Whereas for the traditional groove from (upper part of the picture), the air within the bore hole (blue) is compressed to the bottom, the multi-groove (lower part of the picture) allows for the air to escape and for the MQL-aerosol (yellow) to sufficiently wet the bore hole wall.
Through the improved washing effect of the multi-groove, the outgoing air removes the occurring material particles from the part already during processing.