English to Russian Tech/Engineering Mechanics / Mech Engineering тип пуансона

Concave Shear - это тип пуансона. Как его обозвать по русски?
Контекст на http://www.wawhitney.com/Tooling.html :

36TC Punches are available up to 5.000" (127 mm) in diameter. All round punches through 1.719" (43.66 mm) diameter (or equivalent size shape) are flat faced (Style I). Punches 1.720" (43.69 mm) through 2.469" (62.7 mm) in diameter are standard with 1/4" (6.35 mm) concave shear (Style II). Punches 2.470" (62.74 mm) and larger are standard with 7/16" (11.11 mm) shear (Style III). **Concave shear** punches are not recommended for material over 1/4" (6.35 mm) thick. House top shear punches are recommended for material over 1/4" (6.35 mm) thick and for high shear strength materials. Other shear types are available at customer request.

Нужно срочно! Есть идеи?