Drilling a brake disc carrier?

[BBadger]

To those of you who know your engineering know how and what not i have a question.

If i were to take a 4 bolt break disc (probably 300-320mm) turned 45degree and the bolt holes drilled a few mm further out but still on solid metal.

Would this compromise the disc and cause it to fail on me in some way?

Or if you think this a stupid idea does any one know of anywhere that i would be able to find a "blank disc", whole but without the bolt holes drilled?
or should i bite the bullet and get custom disc makers to make me one up.

Thanks
Badger

[Sid Squid]

What's the diameter of the centre hole, the width of the centre circle*, what size are the existing holes and what size will your new ones be, and how far from the edge?

*By which I mean if you were to take just the bit where the bolts go, what size is that circle - inner and outer?

[Specialone]

That would be incredibly difficult to do accurately, needs to go on a miller really so it can be done with precision.

Take a photo and overlay where you want the new holes so we can see, I'm struggling to see exactly what you want tbh.

[Sid Squid]

BBadger wants to use a disc which has it's mounting holes in a smaller PCD than the bolt holes in the wheel, to do this he wants to drill four new holes equidistant between the originals but on a slightly larger circle.

[Specialone]

BBadger wants to use a disc which has it's mounting holes in a smaller PCD than the bolt holes in the wheel, to do this he wants to drill four new holes equidistant between the originals but on a slightly larger circle.

Oh good, I had understood then :)

Does he realise that this is a precision job?

[Sid Squid]

Oh good, I had understood then :)
I thought so - I realised you were just making certain of the question. :D
Does he realise that this is a precision job?
I hope so.

[yorkie_chris]

My gut feeling is try it and keep eye out for any signs of distortion provided the holes do not end up dangerously close to the outside of the carrier or any lightening holes in the carrier.

[BBadger]

yes this is the general idea and i have someone who can do the cnc work for me but its just a matter of do you think im wasting my time ..... could it cause structure issues if the holes get close to an edge?

or

just a flat 320mm made up from somewhere like This Lot (http://www.allbikeengineering.co.uk/html/discs.html)

[Sid Squid]

Don't bother answering the questions - just guess.

[BBadger]

is there a keithd option for this guess?

[yorkie_chris]

What Sid asks is pretty much what we need to have an educated guess about whether it is possible or not...

[BBadger]

i know, im just not at home for a week so cant get some good measurements on it.

[monkey]

Here's my guess: if you're drilling within 0.005mm of the edge of the carrier then it will fail and your balls will fall off in the resulting mess. If you leave 25 yards of material and reinforce it with blue tac it will be fine and people will gasp in awe as you ride past them.

[Sid Squid]

Here's my guess: if you're drilling within 0.005mm of the edge of the carrier then it will fail and your balls will fall off in the resulting mess. If you leave 25 yards of material and reinforce it with blue tac it will be fine and people will gasp in awe as you ride past them.
Perhaps not the most finely crafted engineering answer - but undoubtedly entirely true.

Well, maybe not the BluTack bit. But all the rest of it for deffo.

[yorkie_chris]

Perhaps not the most finely crafted engineering answer

Indeed, fancy mixing metric and imperial like that. Who does he think he is British Leyland...

[Sid Squid]

Indeed, fancy mixing metric and imperial like that. Who does he think he is British Leyland...
Good point - I didn't spot that.

Metric, Imperial, UNF, BA, Cycle, Gas, AN, Whitworth and who knows what else - perhaps I'm desensitised.

[monkey]

That was a deliberate error waiting to be spotted. 25 yards is obviously 22 860mm which would have been the correct way to display that particular measurement.

[Sid Squid]

1.5280966163e-10 AU
50.8 Egyptian cubits
7.4084216804e-16 Parsecs

[Specialone]

Indeed, fancy mixing metric and imperial like that. Who does he think he is British Leyland...

BL didn't do it on purpose, it was all they could find in the bolt tin.


My old man was a foreman at BL in the 70's before he died, obviously all the cars he had anything to do with were perfect :)

[BBadger]

i leave you all unattended for a day and look what happens to my nice tidy thread!

[monkey]

Sorry little one. Take some pics and get them up so the clever ones can make a proper guesstimate for you.

[timwilky]

Indeed, fancy mixing metric and imperial like that. Who does he think he is British Leyland...

When I was seconded to technical service. I received a very strange call from a dealer.

We have just opened your new manual for the 680 engine ( goes back to the dark age) and notice the head studs are 12mm. We have just fitted new studs and stripped the block. when we mic'd up the old studs the were 1/2".

Turned out tech pubs had gone metric and somebody had written nearest equivalents.

[embee]

30cm plastic rulers, £2 19s 11d a dozen. That's metric for you. :)

[Sid Squid]

680 engine
Leyland 680 - as in bus motor?

You remember when they were new? You're older than you look!