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・ Is the pilot hole of the forming tap appropriate?
After machining the forming tap , it is possible that the amount of raising is too large, and the height of the thread pile exceeds the target range.
* The pilot hole diameter table in forming tap is for reference only.
Depending on the workpiece material, the elevation will change, so please consider adjusting to increase the pilot hole diameter. In addition, if the drill is not sharp enough for the workpiece material, the hole diameter may be reduced after drilling. This happens when the hole is pushed wide without cutting due to lack of sharpness, and the material tries to return to its original shape after the drill is removed.
As an example, this phenomenon is likely to occur when processing SUS and mild steel with carbide drills for general steel. Check the wear of the cutting edge and the material compatible with the drill.