Anyone here ever tried to cross drill their own brake rotors with a drill press? I hear the holes in the rotors makes for more effective braking... I know I would have to use a lot of WD40 to keep the drill bit cool, but it might be worth it. I would just be afraid the rotors would crack afterwards or warp from the heat. I'm all about going fast, but eventually I would like to stop again too. :beer2:
Question: Cross drilling brake rotors...
- Thread starter SgtKilroy
- Start date
I'm not a big fan of drilled rotors. Yes, you can run into problems with cracking.
If you are going to do it, yes, use oil or WD to keep the bit from dulling. They are cast iron and drill easy. Also get a chamfer tool, and put at least a .030" chamfer on the holes so they resist cracking as easy.
If you are going to do it, yes, use oil or WD to keep the bit from dulling. They are cast iron and drill easy. Also get a chamfer tool, and put at least a .030" chamfer on the holes so they resist cracking as easy.
I appreciate the input. My rotors are about half way through their life so I figured why not give it a shot? I wanted to buy new rotors anyhow. I will do a write up as best I can. I figure 1/4 inch holes interspersed in a forward "spiral" should work. Hopefully someone else on here has tried this and has some tips.
Since they are vented discs, you have to drill from both sides, not just one. Drill just until it breaks through to the middle.
Go to Enco, Harbor Freight, Rutland, and get a cheap rotary table. You will also need a dial indicator that fits into the chuck. Put the indicator into the chuck, with the rotor visually centered on the rotab and clamped down (this should really be done on a mill, but eh). Now rotate the rotab, and mark the high point, and zero the indicator on the low point. Loosen clamps to finger tight. Tap on rotor till the indicator reads the average from high to low readings. Rezero. Spin again. You are done when you get it to about .010" max on the high-low reading. Clamp tight, and spin to make sure clamps didn't move it.
If you use a 90deg #4 center drill, you won't need a chamfer tool. Chuck the center, and position the head to the radius of the first pattern. Spin your rotab to 0 deg. Come down until the center drill dia is about .280" for 1/4 holes. Switch to 1/4 drill (HSS at a minimum, don't use "carbon steel" bullshit), and punch through. Rotate to the next position and repeat.
To get a spiral, you are going to shift your zero deg start point progressively as you go to each new track. Say you want 5 tracks, with 20 holes. Do your 18 deg rotations from zero for track one, then go up in even increments on the start point. 0, 5, 10, 15, 20 deg start points. For a more elegant look, go 0, 3, 7, 12, 18.
Measure your rotor and draw the pattern you want on CAD or graft paper before you start. Finding that your pattern won't work after you started would suck.
Go to Enco, Harbor Freight, Rutland, and get a cheap rotary table. You will also need a dial indicator that fits into the chuck. Put the indicator into the chuck, with the rotor visually centered on the rotab and clamped down (this should really be done on a mill, but eh). Now rotate the rotab, and mark the high point, and zero the indicator on the low point. Loosen clamps to finger tight. Tap on rotor till the indicator reads the average from high to low readings. Rezero. Spin again. You are done when you get it to about .010" max on the high-low reading. Clamp tight, and spin to make sure clamps didn't move it.
If you use a 90deg #4 center drill, you won't need a chamfer tool. Chuck the center, and position the head to the radius of the first pattern. Spin your rotab to 0 deg. Come down until the center drill dia is about .280" for 1/4 holes. Switch to 1/4 drill (HSS at a minimum, don't use "carbon steel" bullshit), and punch through. Rotate to the next position and repeat.
To get a spiral, you are going to shift your zero deg start point progressively as you go to each new track. Say you want 5 tracks, with 20 holes. Do your 18 deg rotations from zero for track one, then go up in even increments on the start point. 0, 5, 10, 15, 20 deg start points. For a more elegant look, go 0, 3, 7, 12, 18.
Measure your rotor and draw the pattern you want on CAD or graft paper before you start. Finding that your pattern won't work after you started would suck.
Holy crap... I take it you have done this before. That's exactly what I was looking for. Thank you!:beer2:
It will be cheaper and easier to buy them already drilled and slotted. I bought a set of 4 rotors and pads for my 2500hd to my door from cali for $400
So basically this would be a waste of time? I'm the new guy here, so I will gladly defer to the more experienced guys.
Last edited:
If you tow heavy or race, the fronts will surface crack without drilling. Surface cracks ain't a big worry, but if you give them an area to "grow" into, they change to full cracks.
No, I haven't done this on a Dmax, but other vehicles. And I was a machinist for about 10 years doing mostly prototype work.
No, I haven't done this on a Dmax, but other vehicles. And I was a machinist for about 10 years doing mostly prototype work.
Bingo. Just to buy the rotab, indicator, etc, would be $400. And it takes a LONG time to do without a CNC mill.
I have found some relatively inexpensive rotors, but I wrongly assumed it would be cheaper to do the modification on my own.
http://www.autopartswarehouse.com/s...R.html?tlc=Brakes,+Suspension+&+Steering?tlc=
http://www.autopartswarehouse.com/s...R.html?tlc=Brakes,+Suspension+&+Steering?tlc=
I don't think it will have any effect on unladen braking distance. It might hurt laden braking distance though, but I doubt very much.
It's a popular modification for cars and trucks, but do not expect any kind of advantage other than looks out of it. Racecars seldom have drilled discs anymore.
It's a popular modification for cars and trucks, but do not expect any kind of advantage other than looks out of it. Racecars seldom have drilled discs anymore.
i have found that they do not stop any shorter distance or any firmer, but they dont get as hot as the stock rotors did.
Since they don't get as hot, would that make them last longer? Hotter rotors are easier to wear down right?
idk, ive had them on for a yr and a half. they seem to last longer. they didnt warp like the 2 sets of rotors i had previously had on the truck
Last edited: