Reverse taper shanks and complementary base block bores for bit assemblies

A combination bit holder and base block comprising:

• a bit holder having an upper body portion and a generally hollow cylindrical slotted shank depending therefrom, the shank sized to be non-rotatably mountable in use in a base block bore,
• a first portion of said shank adjacent a distal end thereof, the first portion including an outer surface of increasing diameter toward said distal end of said shank, and
• the base block comprising a receiving portion including the bore therein for receiving and holding said shank, said bore including a portion generally corresponding in hollow dimension to hold said first portion of said shank in compression at a similar position from a top of said bore as said first shank portion is from a bottom of said upper body portion.

A combination bit holder and base block comprising:

• said bit holder including a generally cylindrical hollow slotted shank, an outer surface of said shank including a frustoconical reverse taper segment adjacent a distal end thereof,
• said base block including a bore therein, said bore having a constant reverse taper portion generally complementary to said reverse taper segment of said shank when said shank is inserted in said bore, the shank sized to be securely mountable by elastic radial compression against the bore of the base block, and
• a widest part of said shank, when inserted in said base block bore past a top of said bore reverse taper portion, adapted to bias said shank to be fully inserted in said bore.