The complete Hollow Stem Auger string is shown at the left. The numbers correspond with the numbers on each of the following pages of our stocked auger sizes.  Our stocked hollow stem augers are 5 feet (1.5 meters) long and range from 2 1/4" I.D. to 12 1/4" I.D. (5 5/8" O.D. to 17" O.D.).

(1) The Hollow Stem Auger itself is made up of a premium carbon steel tube, 3/8" thick hard-faced carbon steel flighting, and 4142 heat-treated alloy steel tool joints.  Mills Machine Standard Duty Hollow Stem Augers are designed for use in shallow hole applications up to 70 feet.  For deeper drilling, Mills Machine Heavy Duty Hollow Stem Augers should be used, featuring heavier, tapered tool joints, larger bushing nuts, larger lock bolts, and larger drive keys, for added strength.

(2) The Auger Drive Cap connects the auger string to the rig's drive.  It features a hex pin connection to match the rig's drive (1 5/8", 2", etc.) and box connection to match your auger string.   

(3) The Nut & Bolt for the Rod-to-Cap Adapter holds the Rod-to-Cap Adapter in place inside of the drive cap.

(4) The Auger Pilot Bit Connector connects the internal drill rod to the auger pilot bit and also centers the pilot bit. 

(5) The Rod-to-Cap-Adapter connects the drive cap to the drill rod string, enabling the drill rods and the pilot bit to turn in tandem with the auger string.

(6) Auger Drill Rod

(7) Auger Lock Bolts

(8) Auger Bushing Nuts

(9) Auger Drive Keys

(10) Auger Cutterheads cut the O.D. of the hole for the auger.  Mills Machine cutterheads come in 6 different variations: Blade, Spade, Blade/Bullet, Spade/Bullet, Bullet, and 5-T.  Read more about these in Section 2: Hollow Stem Auger Components, Auger Cutterheads.

(11) Auger Pilot Bits are connected to the drill rod with the Auger Pilot Bit Connecter and fit into the center of the Auger Cutterhead to drill the center of the hole.  Mills Machine pilot bits come in either Apex or Bullet types.  Read more about these in Section 2: Hollow Stem Auger Components, Auger Pilot Bits.