TUNING  AN HS-400 HIGH SPEED DRIVE UNIT When you receive your nail feeder, the HS-400 drive unit has been factory tuned with the proper number of springs and with the correct coil gap.  Nothing should be added to the bowl.   If the unit is operated at a high amplitude,  i.e. over 1/4" (6mm), for an extended period of time there could be some spring breakage. When replacing springs it is very important that the springs be TIGHTENED SECURELY.  5/8" bolts should have a torque of 400ft lbs. and  3/4" bolts 800ft lbs.  (Bolts should have a depth of approximately twice their diameter). OTHER THINGS TO CHECK: Spring clamp blocks  must be used under the head of the spring bolts. Spring spacers must be used between the springs and against the fastening surfaces. The armature air gap should be between  .125" (3mm).  If the gap is larger than this the coils may burn out.. The proper controller must be used.  Input voltage must be the same as that of the controller and the coils. The bowl mounting bolts must be tight. (Torque should be approximately 150 ft. lbs). Nothing should restrict the bowl from vibrating. The stand for the feeder should be substantial,  level and vibration free.