How To Use 801 (INCH) Blake Coaxial Indicator Centering Device

How to Use a Coaxial Indicator


The Blake COAXIAL (co-ax) indicator is primarily as a precision centering instrument for locating a work piece on a horizontal or vertical machine tool while the spindle rotates under power. Learn how to use a Blake coaxial indicator.

The Blake COAXIAL (co-ax) indicator is equally useful for positioning in the situation where it may be desirable to turn the spindle by hand the direction and distance of location error may be determined thus:

DIRECTION is indicated by the radial position of the feeler when the hand is at its high, or low, point of travel.

DISTANCE is indicated by the total travel of the indicator hand thru one full revolution of the machine spindle.


  • The STRAIGHT FEELER is used for inside diameters to approximately 4.25” inches.
  • The CURVED FEELER is used on outside diameters to approximately 4.25” inches and may be used on inside diameters over approximately 1 inch.


  1. Pre-position work to within the indicator travel range.
  2. Attach restraining are to indicator and ensure there is a suitable stop in place. This will keep the indicator from rotating while spindle is operating so operator can easily and conveniently read the dial.
  3. Place appropriate feeler in indicator rocker bracket and secure with thumb-screw. Position rocker bracket on rocker friction joint such that small indicator hand is centrally located on its graduation scale when feeler is in operational contact with work-piece.
  4. Start machine spindle. CAUTION: Check for interference before turning on power. Speed should not exceed 700 to 800 rpm at any time.
  5. Move machine table along axis of one positioning screw to a point where the indicator hand travel range has diminished to its lowest distance, thus, indicating that the center is centered in the spindle plane in the one direction.
  6. Move the machine table along the axis of the other positioning screw until the indicator hand travel range diminishes to zero, thus indicating that the work-piece center is in axial alignment with the machine spindle.NOTE:     STEPS 5 & 6 will need to be repeated until needle movement reduces to ZERO movement. )The Blake CO-AX (co-axial) indicator is fitted and tested for operation of at least 58° F.  Bearing stiffness may be present at lower temperatures.


DIAL GRADUTAION is divided such that each division represents .0005 inch of AXIS OFFSET (deviation from true location) when the feeler is tracing a diameter of two inches.  (Varies slightly with feeler angle.)  [Note: Dial graduation is different for 801-E Economy model.]


Under normal conditions The Blake COAXIAL (co-ax) indicator should require no servicing and only the consideration in use and handling due any precision instrument.  Allowance for familiarization should be made when it is first being used.