To provide a stepped concrete pin capable of securing even a holding force, while reducing penetration resistance in the initial stage of driving.
This concrete two-stage pin 1 is formed by connecting a large diameter shaft 13a at the expanded diameter head side and a small diameter shaft 13b at the tip side via a tapered step 5, and characterized by forming a plurality of vertical grooves 7 in parallel with one another in the axial direction on the peripheral surface of the shaft. Instead of forming a knurling groove on the peripheral surface of the large diameter shaft 13a, a chemical 11 may be applied to a part or the whole peripheral surface of the small diameter shaft 13b and the large diameter shaft 13a for preventing the concrete pin from coming off from concrete.
BAN TAKANORI
HOJO TAKAO
KOBAYASHI KUNITAKA
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