Brake Disc Drilling

This project always seemed to call for a balance between 'factory cafe' and 'custom cafe'.  Thus drilling the front disc had always been part of the project plan.  However, the small risk of creating an un-appealing design or instigating some other disaster kept me from tackling this until now.  Using a neighbor's drill press and a fresh new 1/4" metal drill bit, I finally got started.

First, the pattern and total number of holes; I'd planned on a slightly curved forward arch and more holes, but as I devised a way to mark each hole prior to drilling, the accuracy of each hole placement became a concern.  I thus decided on a slightly more uniform or symmetrical pattern similar to that on my Triumph 675 front discs.  This helped ensure that spacing was uniform.  30 holes will not save a lot of weight nor make the bike stop faster, but I did it primarily for the new experience as well as aesthetics.


Marked the holes with a Sharpie

 Then scored each with a Dremel















Setting up the drill press; mostly wanted to ensure that the disc was flat and that it was fairly secure to the press before each drilling.  This set up worked to accomplish this and still made it easy to rotate the disc and line it up for the next hole.  I also scored each hole mark first with a Dremel tool to prevent the drill bit from wandering (although using a press this was not likely).  Either way, it worked well.

Each hole took only 20 seconds or so, applying intermittent pressure and some cutting oil.  I went around once skipping every other hole, then finished the rest off.  With a total of 30 holes, the whole process took me roughly an hour and a half; much faster than I'd expected.  That includes slightly counter-sinking both sides (60 total) of each hole to take the sharp edge off.

I later ground off some of the rough inner casting with a Dremel tool; then taped off the swept area and painted the inner disc with some semi-gloss black paint before mounting the disc back on the front wheel.