Cross drilling rotors yourself? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

knucklebuster · 12-13-2003, 08:47 AM

Is it possible?I've always wondered this?Or would it make them weak

Andy4639 · 12-13-2003, 09:45 AM

I have also wondered about doing them myself. As long as you stay away from the edges, I don't see anything wrong with it. I may be wrong but , you now that they can be done.

jamis · 12-13-2003, 10:08 AM

There really is no need for it IMO. You would realy have to drive aggressively to take advantage of drilled rotors. It will also weaken the rotor so it would most likely crack or warp when you hit a puddle with hot brakes.

nu2-72 · 12-13-2003, 11:45 AM

To cross drill correctly you would next an index table. If you look at those sold by the name brands, they are not just drilled. They are symetrical and overlapping and chamfered. By this I mean that they are equal distances around the rotor, and equally offset in each row. This allows the holes to cover the entire pad area. We all have seen what happens when one rivet contacts a rotor. A groove is formed. This can happen with a void in the hole pattern and ruin a brake rotor. Actually doing more damage than good. Most also have " ( " slots cut in them. This covers the entire pad and helps clear pad material. The holes provide cooling.
Yes it can be done with the right tools.
A drillpress won't cut it. We are talking about brakes and your life if one fails.
Just my .02

*Shane* · 12-13-2003, 11:47 AM

I agree with nu2-72. Find yourself a friend with a Bridgeport style knee mill and an indexing table ... even better yet would be a machine shop with a CNC vertical machining center.

Doing this with a hand drill or a drill press is going to be tough work.

slam33 · 12-13-2003, 12:01 PM

nu2-72 is right and if you don't get them right they will be out of balance

*Gee_Emm* · 12-13-2003, 12:15 PM

I have done this and it turned out great. I did this a few years ago. I used a computer drafting program and made a circle the same size as the rotor, I then layed out lines in a pie shaped pattern, drew a couple circles equal distance apart on the rotor surface area. This will give you 2 intersecting lines, put a circle in the correct spot to make the pattern. I then printed out the pattern on paper cut it out and layed it on the rotor, took a center punch and made a mark for all the hole and drilled them out. You will for sure need a drill press to do this. After they were all drilled I went around and chamfered them all with a slightly larger bit. It turned out looking just as good as any other drilled rotors. Can't tell you how they will perform as the truck hasn't been driven yet. I will see if I can scrounge up some pictures in the next couple days.

tom hand · 12-13-2003, 12:25 PM

Ok...somebody's got to disagree. I have seen articles in mags on this I think it would be a piece of cake. An indexer won't help much because the trick is to lay out the holes so you don't drill through the ribs in the rotor. So you can't just index it where it looks good and start drilling. Lots of patience, tape and measuring, and you can lay out the holes by hand...the first one will take a while...the second will be easy. You can easily drill it with a drill press. Go to a junkyard or brake shop and get a couple of junk ones to practice on before you drill the ones on your truck. Good Luck

*rickspickuppart* · 12-13-2003, 12:59 PM

for all that effort, wouldn't it just be better to go to Checkers or Autozone and buy them (we got our last set from Autozone - they have to order them)

Shawn

jef5150 · 12-13-2003, 01:17 PM

those rotors are drilled and milled in a cnc machine ,they are programmed to be a "specific" distance from each other,probably (+-0005).Using a drill press, you'll be lucky to be within .050,, ,,,, also each "grouping of holes" is again a specified distance from each other.I've been doing ultra-precision machnining for almost 20yrs,im "STRONGLY ADVISEING" you "NOT" to do this your self,,,, YES,it can be done in a drill press,i can only give my advise.If you try it, buy a counter sink to de-burr the holes,a drill has 2 flutes on it,and it will more than likely leave a burr which will cut up your pads,,,,,,,,,jeff,,,,,,,use a machine!!!!!!

**N2TRUX** · 12-13-2003, 01:28 PM

I think if you are really bored, and have way too much time on your hands it can be done. My question is "why"? You can buy drilled and slotted rotors so cheap these days it's not worth it.

PDX68GMC · 12-13-2003, 01:28 PM

I'm going to say bad, bad, idea.

Unless you really do a boatload of high-speed braking, and do this frequently, you wouldn't even really notice the brake fade that cross-drilling helps. Like during a SCCA SOLO II race.

If you were very successful in doing the drilling, you'd still have to inspect the rotors very often as they tend to develop cracks around the holes.

Instead, I'd get a set of Powerslot rotors, which don't crack, or change all the brake fuild to a higher spec synthetic fluid.

YMMV

-PR

Steven Sellers · 12-13-2003, 01:48 PM

I was watching two guys garage last weekend and they were HEAVILY against it but of course they are trying to sell product.

In my job we had to deal with many tolerances all the way to micro inches and I just dont see a drill press being accurate to be even close to what you need, but who knows I havent tried it.
I personally wont do any modding to brakes due to I have family that I want take that chance with.

Dont shoot me just my opinion
Steve

casey · 12-13-2003, 03:15 PM

cross drilling is fine as long as you don't cross dress, you'll be ok. LOL seriously though I have a question would a factory drilled rotor be made of stronger material than a regular rotor, the offshore regular rotors don't look like I'd want to drill them full of holes. ?????

knucklebuster · 12-13-2003, 05:38 PM

I'm not saying I'm gonna do it,I was just thinkin and wondered if it could be done?Thanks for all your advise and tips fellas.I wasn't really worried about doing it for performance reasons but just like the look of them.I guess I'll just break down and buy some.

cableguy0 · 12-13-2003, 08:58 PM

working in a machine shop myself i wouldnt even do it. it would take too much time and effort and they are too cheap new to risk it. i would be led to believe that a stock rotor with a bunch of holes drilled in it is gonna be weaker more prone to cracking and warping. and as someone else said it unless your driving on a road course at high speeds and doing a bunch of high speed breaking you dont need it.

12-13-2003, 08:47 AM	#1
knucklebuster Failure is NOT an option! Join Date: Feb 2003 Location: greenwood s.c. Posts: 811	Cross drilling rotors yourself? Is it possible?I've always wondered this?Or would it make them weak __________________ House payment or truck parts?????.........why does life have to be so complicated? 1969 Chevy Shortbed Fleetside 1969 Camaro ps pb a/c(drove in high school now it's just a yard ornament,but it's next on the list for resto) 1990 Ni$$an hardbody( daily beater that has been really beaten!) 1999 Grand Am GT(wifes ride...never buy a pontiac!!Trust Me)

12-13-2003, 09:45 AM	#2
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Drilling I have also wondered about doing them myself. As long as you stay away from the edges, I don't see anything wrong with it. I may be wrong but , you now that they can be done. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

12-13-2003, 11:45 AM	#4
nu2-72 Senior Member Join Date: Apr 2001 Location: Amazonia, Mo. USA Posts: 2,821	To cross drill correctly you would next an index table. If you look at those sold by the name brands, they are not just drilled. They are symetrical and overlapping and chamfered. By this I mean that they are equal distances around the rotor, and equally offset in each row. This allows the holes to cover the entire pad area. We all have seen what happens when one rivet contacts a rotor. A groove is formed. This can happen with a void in the hole pattern and ruin a brake rotor. Actually doing more damage than good. Most also have " ( " slots cut in them. This covers the entire pad and helps clear pad material. The holes provide cooling. Yes it can be done with the right tools. A drillpress won't cut it. We are talking about brakes and your life if one fails. Just my .02 __________________ 72 3/4 4x4 350 4spd 72 3/4 4x4 350 auto 2004 Duramax Silverado 4x4 2006 Duramax Crew cab 4x4 2010 Harley Ultra Limited 2011 Harley Street Glide

12-13-2003, 12:01 PM	#6
slam33 Registered User Join Date: Aug 2001 Location: Long Beach, Ca Posts: 1,432	nu2-72 is right and if you don't get them right they will be out of balance __________________ 71 LWB 350/350still working on it but it's going tp be sweet. www.geocities.com/stevemau/slam33page.html " TARGET=_blank>http://www.geocities.com/stevemau/slam33page.html?1004806705410 </A>

12-13-2003, 12:25 PM	#8
tom hand CCRider Join Date: Feb 2000 Location: Olive Branch,MS,USA Posts: 2,232	Ok...somebody's got to disagree. I have seen articles in mags on this I think it would be a piece of cake. An indexer won't help much because the trick is to lay out the holes so you don't drill through the ribs in the rotor. So you can't just index it where it looks good and start drilling. Lots of patience, tape and measuring, and you can lay out the holes by hand...the first one will take a while...the second will be easy. You can easily drill it with a drill press. Go to a junkyard or brake shop and get a couple of junk ones to practice on before you drill the ones on your truck. Good Luck __________________ 72 GMC Sierra SWB almost finished---- 84 Softail Olive Branch MS

12-13-2003, 10:08 AM	#3
jamis F.A.S.T. president Join Date: Sep 2003 Location: Florida Posts: 1,883	There really is no need for it IMO. You would realy have to drive aggressively to take advantage of drilled rotors. It will also weaken the rotor so it would most likely crack or warp when you hit a puddle with hot brakes.

12-13-2003, 11:47 AM	#5
Shane Account Suspended Join Date: Jun 2000 Location: over yonder Posts: 14,270	I agree with nu2-72. Find yourself a friend with a Bridgeport style knee mill and an indexing table ... even better yet would be a machine shop with a CNC vertical machining center. Doing this with a hand drill or a drill press is going to be tough work.

12-13-2003, 12:15 PM	#7
Gee_Emm Account Suspended Join Date: Sep 2000 Posts: 4,002	I have done this and it turned out great. I did this a few years ago. I used a computer drafting program and made a circle the same size as the rotor, I then layed out lines in a pie shaped pattern, drew a couple circles equal distance apart on the rotor surface area. This will give you 2 intersecting lines, put a circle in the correct spot to make the pattern. I then printed out the pattern on paper cut it out and layed it on the rotor, took a center punch and made a mark for all the hole and drilled them out. You will for sure need a drill press to do this. After they were all drilled I went around and chamfered them all with a slightly larger bit. It turned out looking just as good as any other drilled rotors. Can't tell you how they will perform as the truck hasn't been driven yet. I will see if I can scrounge up some pictures in the next couple days.

12-13-2003, 12:59 PM	#9
rickspickuppart Account Suspended Join Date: Jul 2003 Posts: 1,284	for all that effort, wouldn't it just be better to go to Checkers or Autozone and buy them (we got our last set from Autozone - they have to order them) Shawn Last edited by rickspickuppart; 12-13-2003 at 01:04 PM.

12-13-2003, 01:17 PM	#10
jef5150 Inline 69 Join Date: Apr 2003 Location: valleysprings,california Posts: 1,018	just my opinion/advise,,,,,,,,,,,,,,,, those rotors are drilled and milled in a cnc machine ,they are programmed to be a "specific" distance from each other,probably (+-0005).Using a drill press, you'll be lucky to be within .050,, ,,,, also each "grouping of holes" is again a specified distance from each other.I've been doing ultra-precision machnining for almost 20yrs,im "STRONGLY ADVISEING" you "NOT" to do this your self,,,, YES,it can be done in a drill press,i can only give my advise.If you try it, buy a counter sink to de-burr the holes,a drill has 2 flutes on it,and it will more than likely leave a burr which will cut up your pads,,,,,,,,,jeff,,,,,,,use a machine!!!!!! Attached Images

12-13-2003, 01:28 PM	#11
N2TRUX Happy to be here Join Date: Mar 2000 Location: Cypress, TX Posts: 39,023	I think if you are really bored, and have way too much time on your hands it can be done. My question is "why"? You can buy drilled and slotted rotors so cheap these days it's not worth it. __________________ Follow me on Facebook and Instagram @N2trux.com Articles- "Jake" the 84 to 74 crewcab "Elwood" the77_Remix 85 GMC Sierra "Scarlett" "Refining Sierra"

12-13-2003, 01:28 PM	#12
PDX68GMC Registered User Join Date: Dec 2003 Posts: 4	I'm going to say bad, bad, idea. Unless you really do a boatload of high-speed braking, and do this frequently, you wouldn't even really notice the brake fade that cross-drilling helps. Like during a SCCA SOLO II race. If you were very successful in doing the drilling, you'd still have to inspect the rotors very often as they tend to develop cracks around the holes. Instead, I'd get a set of Powerslot rotors, which don't crack, or change all the brake fuild to a higher spec synthetic fluid. YMMV -PR

12-13-2003, 01:48 PM	#13
Steven Sellers Registered User Join Date: Jan 2002 Location: North Carolina Posts: 692	I was watching two guys garage last weekend and they were HEAVILY against it but of course they are trying to sell product. In my job we had to deal with many tolerances all the way to micro inches and I just dont see a drill press being accurate to be even close to what you need, but who knows I havent tried it. I personally wont do any modding to brakes due to I have family that I want take that chance with. Dont shoot me just my opinion Steve __________________ 2008 Buick Enclave(wifes new non wrecked) 1996 Jeep Cherokee 2002 2500HD 6.0L (traded) 1998 Jeep Grand Cherokee(wifes/wrecked) 1977 DJ5 postal jeep(mmm lots of fun) 1988 Toyota 2wd p/u(DD, blewup 199,000) 1991 Toyota 2ed p/u (sry just cant break these things) 1997 XR70 Honda 1991 Z50(FOR SALE) 1972 Z50 Honda 1970 SWB 350/knucklebuster "The adventure begins and I am confident that there will be no end".

12-13-2003, 03:15 PM	#14
casey Registered User Join Date: Jan 2003 Location: Kelowna B.C. Canada Posts: 2,048	cross drilling is fine as long as you don't cross dress, you'll be ok. LOL seriously though I have a question would a factory drilled rotor be made of stronger material than a regular rotor, the offshore regular rotors don't look like I'd want to drill them full of holes. ?????

12-13-2003, 05:38 PM	#15
knucklebuster Failure is NOT an option! Join Date: Feb 2003 Location: greenwood s.c. Posts: 811	I'm not saying I'm gonna do it,I was just thinkin and wondered if it could be done?Thanks for all your advise and tips fellas.I wasn't really worried about doing it for performance reasons but just like the look of them.I guess I'll just break down and buy some. __________________ House payment or truck parts?????.........why does life have to be so complicated? 1969 Chevy Shortbed Fleetside 1969 Camaro ps pb a/c(drove in high school now it's just a yard ornament,but it's next on the list for resto) 1990 Ni$$an hardbody( daily beater that has been really beaten!) 1999 Grand Am GT(wifes ride...never buy a pontiac!!Trust Me) Last edited by knucklebuster; 12-13-2003 at 05:40 PM.



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12-13-2003, 08:58 PM	#16
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,950	working in a machine shop myself i wouldnt even do it. it would take too much time and effort and they are too cheap new to risk it. i would be led to believe that a stock rotor with a bunch of holes drilled in it is gonna be weaker more prone to cracking and warping. and as someone else said it unless your driving on a road course at high speeds and doing a bunch of high speed breaking you dont need it. __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

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