Tuesday, October 27, 2009

Accurate Lightening Hole Drilling

Any of you guys have tips on how to get holes accurately marked for drilling on circular parts such as brake drums like this so that they end up evenly spaced? I love lightening holes when done right, problem was most of the time when it was done it was a haphazard job that looks like crap and makes the part dangerous. Is their a mathematical equation to it, or simple method???


  1. Looks like that one used the 8 bolt holes for reference. You can use a straightedge across the centers, then use calipers or another measuring device to center the holes outward. Same for drilling or notching shouldered rims- use the spoke holes for reference and square them across to the outer edge of the ribs. I'm no good at math, but I would think you can take the circumference and divide it by the number of holes you want, mark the outer edge, and straightedge the marks across through the center.

  2. Absolutely brilliant! I feel like a complete idiot now for not seeing that. Need to get the drill press set up. Thanks!

  3. Chopper Dave has a nice shot of a well done front hub on his blog, its on his older posts.