How To Drill Your Bowling Ball

How To Drill Your Ball with the KMT Personal Ball Jig

Prior to Drilling:

  1. Use your best fitting ball to get your drill specs.
  2. Use the span ruler to measure and cut distances from your thumb hole to your ring and middle fingers.
  3. Use the span ruler to measure the bridge (distance between your finger holes).
  4. Use the THUMB ANGLE PITCH CONVERSION table, or contact your ball driller, to obtain your finger and thumb pitches.
  5. Record all this information on a DRILL SHEET for reference.
  6. Use a caliper, ruler, etc… to measure the depth of your finger and thumb holes. Standard depths are approximately 2 ½” for thumb and 2″ for fingers. These depths generally depend on where the CG of the ball is located and your hand measurements.

New Ball Layout:

  1. Choose a layout for your new ball. Refer to the manufacturer’s drilling guide (enclosed with ball) or use one of the guides linked from the GUIDES page. Try to choose a layout with the CG no more than 1″ from the center of your grip.
  2. If you know your PAP (positive axis point), mark that on your ball and create your layout measurements using the span ruler. Otherwise, use the manufacturer’s drilling guide to approximate major pin, CG, and MB (mass bias) or PSA (preferred spin axis). MB/PSA locations are only valid on asymmetric core balls.

Drilling Your New Ball:

  1. Place your new ball in the jig as shown on the VIDEO. Position the ball to first drill your thumb hole. Use the reference guides HERE and the VIDEO information.
  2. Place the required bit into the top plate of the jib. Use WD-40™ or another lubricant to lubricate the brass bushing in the top plate to ensure long life of the bit and bushing.
  3. Once you have the ball locked into the jig, DO NOT REMOVE IT until you are done with the hole you are drilling.
  4. Attach your electric drill and begin drilling the holes. Be sure to back the bit out occasionally and vacuum the debris from the hole. This is also a good chance to check the hole depth using your drill bit as a guide.
  5. Loosen the jig plate, rotate the ball, and tighten the jig down for the drilling of your finger holes.
  6. Drill your finger holes according to the reference guide HERE, again using the VIDEO as a tutorial.
  7. Once the holes are drilled to the proper size, pitch, and depth, you will need to bevel the hole edges. Use the bevel sanding attachment and your drill to lightly bevel the finger and thumb holes.
  8. Install your finger grips and thumb slug (if desired) or bevel the thumb hole to your liking if you plan not to use a thumb slug.

Contact Steve Zoeller at 616-581-2564 or contact KMT Enterprises online for more information.