TRU-SPOT Center Drill Instructions - Model GR300

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The Tru-Spot Center Drill is a precision machine, and must be handled and maintained like other precision machines.

Assembly Instructions

If your unit is shipped without having the jaws assembled in the chuck, the assembly is made as follows:

  1. Each jaw is numbered 1, 2, or 3.
  2. Insert jaw #1 into the top slot in the chuck and turn the wrench in a clockwise direction until the jaw catches on the first thread of the internal scroll.
    It may be necessary to exert some slight hand pressure radially on the jaw to make it engage as the wrench is turned.
  3. Repeat for jaws #2 and #3 in a counterclockwise direction.

Two-Piece 24" & 30" Extension Jaws

Two-piece jaws have a number of slots for engaging the gripping arm. Each slot allows gripping on one diameter + or - 1 inch.
Gripping arm position is changed by removing a single bolt in each arm and replacing in the proper position.

How To Use

  1. Insert the T-handle chuck wrench in the chuck to engage the pinion gear.
  2. Turn the wrench to open or close the jaws as necessary.
  3. While holding the the drill in either the horizontal or vertical position, clamp firmly on the stock.
    Be sure to clamp on the proper jaw step.
  4. Caution: Before drilling, check to be sure that the drill bit will clear the chuck center hole without hitting the jaws.
    Failure to do this could cause the bit to be destroyed.
  5. Turn the throttle on the air unit to start. Adjust the throttle position to the desired speed.
    (In most cases full speed can be used.)
  6. Advance drill bit by applying a uniform pressure on the feed handle. A firm steady pressure will minimize drill bit chatter.

Changing Drill Bits (Collet accepts 12mm shank only, any other size may damage or break collet)

  1. Use the feed handle to extend the drill to position such that the chuck jaws line up with the flats on the collet.
  2. Tighten the jaws on the collet flats which locks the collet. Use a 1 1/16" wrench to loosen the collet nut.
  3. Replace Center-Bit, tighten the collet nut, and release the chuck jaws.
  4. Check to make certain collet will clear jaws before drilling.

Material Clamping

The jaw steps to be used for clamping are shown below. The 12" jaws have four steps.

Step     Stock Diameter in inches     Position     24" jaws Position     30" jaws    
1 2 1/2" - 5 1/2" 5 12 3/4" - 15 3/4"     10 25 3/4" - 28 1/4"
2 5 1/4" - 8 1/4" 6 15 1/4" - 18 1/4" 11 27 3/4" - 30"
3 8" - 11" 7 17 3/4" - 20 3/4"
4 10 3/4" - 12" 8 20 1/4” - 23 1/4”
9 22 3/4" - 24"