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Class Information
Number: 175/390
Name: Boring or penetrating the earth > Bit or bit element > Bit with leading portion (e.g., pilot) forming smaller diameter initial bore > Impact type > Plural larger diameter steps
Description: Apparatus in which the cutting edges of the impact bit are arranged so that the boring outline of the bit will describe at least two peripheral axial steps.

Patents under this class:

Patent Number Title Of Patent Date Issued
8550190 Inner bit disposed within an outer bit Oct. 8, 2013
7938205 Boring head method and boring head for a ground boring device May. 10, 2011
5205366 Superposed drilling device Apr. 27, 1993
4858703 Self-propelled subsoil penetrating tool system Aug. 22, 1989
4749050 Impact tool for tunneling Jun. 7, 1988
4317595 Chisel for a crust breaking facility Mar. 2, 1982
4144941 Directional impact tool for tunneling Mar. 20, 1979
4100979 Pneumatic percussion boring device Jul. 18, 1978
RE29300 Rotary percussion earth boring bit Jul. 12, 1977
4016944 Pneumatic hammer-auger earth boring apparatus Apr. 12, 1977
3960223 Drill for rock Jun. 1, 1976

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