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The following points should be paid special attention to when tapping.
(1) Tap selection
Check whether you are using a tap that is suitable for the type and hardness of the material from the list of suitable materials in the catalog. Depending on the through hole or blind hole, it is also necessary to select a tap in the direction of chip discharge.
・Blind hole
A spiral fluted tap in which chips are discharged to the tap-shank side is suitable.
・ through hole
A spiral pointed tap in which chips are discharged to the direction of travel of the tap is suitable.
・Chips are difficult to connect
For materials where chips become sandy, such as FC, straight fluted tap with a large groove space is suitable.
(2) Pilot hole diameter
In tapping, the pilot hole diameter is very important. For cutting taps, the pilot hole diameter must be within the tolerance of internal thread minor diameter of the thread standard.
If the pilot hole diameter is large within the range, the amount of tap cutting used to process the pilot hole will also be reduced. At the same time, there is more space for chip discharge. Select the pilot hole diameter and prepare it so that it is easy to tap.
At that time, depending on the combination of the workpiece material and the drill, it may be enlarged or reduced from the target pilot hole diameter. Due to the pilot hole diameter, it is necessary to select a drill that matches the material to be worked.
(3) Cutting oil
Cutting oil is very important in tapping. The main effects of cutting oil are lubricity and cooling, which contribute to improving chip discharge and preventing welding. Compared to other tools, tap machining is a tool that advances one pitch in one revolution, so lubricity is important for the performance required of cutting oil. If possible, it is recommended to lubricate with plenty of water-insoluble cutting oil, but even if it is water-soluble, it is important to obtain lubricity at the thickest concentration possible within the recommended range.