Nosey
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| posted on 14/8/05 at 05:41 PM |
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Cross Drilling Discs
I cross drilled a pair of solid discs (back of rally car) cos I was working on a CNC Maching Centre at the time and fancied they would be lighter.
Then the pad material came off. I had cut the pads down cos I didn't have a bias valve.
Bought a bias valve and new discs (just in case) and pads. Am now tempted to drill the discs again (need to lose weight without spending money, and
whats lighter and cheaper than a hole?)
Question is, do you think its something I should be doing at all? Should I counter sink the holes? What do a new pair of cross-drilled look like?
Answers/opinions on a postcard to.........
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Hellfire
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| posted on 14/8/05 at 06:12 PM |
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Drilling the disc's too much will make them lighter but reducing material will not help it perform as a heat sink so will tend to overheat
maybe? My mate did it on his bike... they exploded  fortunately he was fine but the smashed disc did irreperable damage to his caliper. Cost him
dear!
The holes need to be of a pattern to slightly overlap forming a constant scarifying action across the pad face helping to uniformly remove glaze...
I'd c'sink them but I can't see it making much difference apart from aesthetically!
If you're drilling vented disc's they need to be positioned accurately between the vanes... just in case! 
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MkIndy7
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| posted on 14/8/05 at 06:43 PM |
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Can't they be grooved like vented disk are?
It might not save as much weight as drilling but should help stop the pads glazing and also any gas building up under the pads..
If done as you suggest in a CNC Machining centre then from what I remember in PPC they said there'd be no problem with the strength of the
disk.
My dads done them for the Kit car, a Fiesta and a Seat Leon Cupra (all vented and on the Cupra fu**ing Huge!) and we've had no problems with any
of em, they look wicked and certainly don't stop any worse!
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tom_loughlin
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| posted on 14/8/05 at 07:42 PM |
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i would have thought the weight saved by drilling the discs would be negligible, and consideration would have been paid when designing them for the
purpose. i would imagine that they ave been heat treated and drilling them might alter the crystal structure of the disc due to the localised heat
build up, effectively annealing them
just a thought
Tom
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rick q
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| posted on 14/8/05 at 11:46 PM |
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Might be worth reading through this thread on the OzClubbies site
http://www.ozclubbies.com/phpBB2/viewtopic.php?t=947&postdays=0&postorder=asc&start=15
Seems the biggest risk with drilling solid disks is crack generation, so countersinking and the ball bearing trick might be worthwhile
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Hellfire
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| posted on 14/8/05 at 11:59 PM |
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quote:
Originally posted by tom_loughlin
i would have thought the weight saved by drilling the discs would be negligible, and consideration would have been paid when designing them for the
purpose. i would imagine that they ave been heat treated and drilling them might alter the crystal structure of the disc due to the localised heat
build up, effectively annealing them
just a thought
Tom
Disc's aren't generally heat treated as the casting stage pretty much sorts out the grain structure. Drilling them makes no real odds on
solid disc's unless under extreme heating and quenching in which case you would indeed crack them - thermal cracking. However, this would
normally show itself before any failure as a warped disc... in which case you replace them. Almost all none Ford disc's are made in China now as
they are very cheap, the quality of these disc's used to be suspect however this last 2-3 years quality is as good as anywhere else in the
world. They even produce them for HGV, PSV and the like now....
I speak from experience.
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NS Dev
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| posted on 15/8/05 at 07:32 AM |
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my mate uses his pantograph engraver to groove discs, does a very nice job and they work very well.
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Syd Bridge
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| posted on 15/8/05 at 07:53 AM |
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The prime reason for drilling is to vent gases from the disc face. Grooving 'wipes' the pad, and also degasses the pad/disc interface.
If you want to save weight, turn the discs down thinner. Take a look at Formula Fords, 1set of discs per race!
Syd.
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ceebmoj
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| posted on 15/8/05 at 11:40 AM |
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hi,
I believe from talking to Tadld on hear about the set of disks that I bout from him that the way you put a radius on the x drilled holes removes a
stress riser and reduces the likely hood of cracking the disk from the hole. Witch as apparently a problem with some drilled disks
My disks feel really good and the breaking as defiantly improved a good amount with the disks witch are both drilled and grooved. I had been expecting
a bit more noise however I drove a good 500 miles at the weekend and there is no real difference to the noise levels
[Edited on 16/8/05 by ceebmoj]
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