Brake disc drilling

What you probably need is just an engineering workshop. Somewhere with a milling machine and a rotary mount, (Though cast can be nasty stuff as it makes a real mess.

Don't.

Drilling holes in discs causes stress-raisers and the disc will fail premature.

Sure sign is little cracks around the holes, seldom seen by the driver because he is usually not around anymore when the disc scattered.

On quality disks (with holes) they are cast in.

On others (thick , that being miniumal 5 mm) you can search a buddy with a mill and mill 2 parallel stripes (3 mm wide, 1mm deep) in the disc. Patterns are not important but they may not be diametral to the disc center. Should stop glazing.

But then again: it has its use and applications in racing. If you ever need that on your brakes on the open road, your are likely not to live long. Said that: patterns of holes in disks are on at least 3 of my cars. They were in when I bought the disks but their use is not beyond gimmick and needlesly eating diskpads.

Tom De Moor

I think he's talking about the holes where the wheel bolts go, not the holes/grooves where the pads go...

cheers, clive

How will that help Carl with his problem of bolt patterns?

Precision Engineers, Toolmaker. Jig boring, etc. Ideally a small jobbing shop. In general larger Co's are reluctant to take on small machining jobs from members of the public.

A point that should be taken into consideration as well is the safety aspect. I've done a few mods to std brake parts. Redrilling discs, machining calipers and/or making brackets for them etc. Some I have refused because IME as an engineer I believed the results would not be safe, so there is always a chance you won't find any professional engineer to do the job. Mike.

Well he isnt talking about the disk brake swept area but the mounting holes. And for what its worth most disks are cast steel not iron and are drilled afterwards. Never seen "cast in" holes!

I have drilled the mounting holes to suit 5 stud rather than four with no issues and its soft easy to drill stuff.

You mean on the swept area? Any examples? Thought not. I have drilled both bike and car disks without any issues.

Rubbish. Brakes on road cars are crap and too small. Even a moderate bit of brasking causes road car brakes to fade. It is beneficial at the expence of a bit of dust and shorter pad life.

Said that: patterns of holes in disks are on at least 3 of my

Actually they clear gasses that the overworked pads produce reducing fade pretty well. And allow wet disks to work imediately. Why do you suppose they put them in?

If you just want to drill some holes mark them accurately, centrepunch them and use your local college / whatevers drill stand. Its easy stuff to drill.

Yes - if I can find the pictures heh. Disks cracking around the holes is relatively common. Just because it hasn't happened to you doesn't mean it doesn't happen.

Ive seen cracks, its crashes caused by them or fasiled disks that I have yet to see...

I was trying to find a link to pictures I've seen a few ties of a 205 at a trackday that had the discs crack and a bit chunk fell off and deposited him into the barrier heh.

Yes I have seen cracked disks, drilled and otherwise. And flywheels too!

Its shattered and crashed ones that leave you "not around" anymore that I havent seen... Cracks are caused by heat in both drilled and non drilled disks, flywheels etc. yet to see one fly apart because of them!

Precision Engineers - that's the jobbie I'm looking for!! Found a professional looking place that's local so have emailed them, but probably won't be interested. And then also found a more old school looking company who actually say:

"General everyday items from sports car mods, motorcycle builds, specials and anything with mechanical working usually end up here, so I guess our paths will cross at some time."

Sounds like they might be able to help, so emailed them too.

Right, now I need some Capri 2.8i vented discs :)

I've never been good at accurate stuff like that, so I'd rather pay someone who knows what they're doing when it comes to something important like brakes :)

The bolt patterns are actually pretty close and it's been suggested that I could just enlarge the standard holes on the discs slightly so the hubs would fit onto them. Sounds a bit dodgy to me though!

Errrrrm, suggest you read my post again. And maybe keep off the Duvel? :)

I'd say the critical part is the fit of the disc to the collar it locates on. The bolts etc then hold it in place by friction - rather than locating it accurately.

Agreed. drill them larger if its close.If its not then better to redrill in between. Either way its not too critical as long as you are accurate. If you drill it yourself no worries. At a push even a hand held drill and some care would be ok. The bolts shouldnt locate the position but just hold it in place. As long as what you do isnt too radical it will be fine! Get good insurance. And an accurate friend!

Sounds like they might be expensive. Co's that offers specialised services like those, usually charge more than a jobbing shop, which would simply charge on the basis of drilling or boring 5 equi-spaced holes on a given PCD. Whether it was on brake discs or just a similar thickness casting the price would simply be based on the time and possibly the hourly expense of running the machine needed to do the job. All that's needed for your job though is milling m/c. Maybe with a boring head.

EBay? Or £21.17 each from

OK, I'll see what they say. If it's too expensive I'll start looking elsewhere.

Yeah, seen some on ebay which work out at about £40 delivered, which would do for now (mostly experimentation purposes).