MK3 Disk Brake Machining / Grinding Queensland Australia

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CHARGER

CHARGER

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Hi guys,

Getting through the restoration of my MK3 and am looking to get the Disks/Rotors cleaned up.

I took them to a local brake shop on the Gold Coast who advised me they couldn't do them
Due to the material being stainless and that I would need to get a machinist shop to do them
With a high speed lathe.

Reading through old Brits it seems you need to "Blanchard grind" them is that what I need to ask for
If approaching machinist shops?

Can anyone suggest a place that can do them on the Gold Coast / Brisbane?

Cheers
 
Is the disc actually gouged or just rusted up a bit.

If just rusted up a bit, you can stone it clean. I have done this some time ago with a new 2 sided 6x2x1 sharpening stone. I used mineral spirits and used multi directional action to create a nice cross hatch pattern and to maintain trueness. Kind of like dressing a draw die after plugging dent. To be able to take off too much material by hand is very inlikely. Keep steady pressure and move around consistantly.

Turn some rugby on the telly and by the time to game is over, you'll be done.

If gouged up, you may want a new one.
 
The Surfaces I would say are passable, no Gouges or lines, I had a quick go this afternoon with some sandpaper on the Bottom disk that still has half a shiney
surface and half rust "Is that a Chrome Coating" or is that "stainless" peeling off?? looks like I need to get rid of that first that's why I was hoping
just to get them ground somewhere.
MK3 Disk Brake Machining / Grinding Queensland Australia
 
Agreed, that more than hand work could fix. As you search for a grinding facility, keep an eye out for another disc. It maybe too far gone.
 
The whole platter is dull finish chrome plated and yes this one is too far gone to show off for nods on this picky forum or for concours points but plenty good for great function once the rest of the chrome removed. Turning mill for new surface as common for car brakes leaves cut lines inline with friction direction which degrades the friction grip detectably so the hand stone or other methods is preferred.
 
I chucked mine up in a lathe and finished removing the chrome, then polished with emery. Bites well (on IRON, as it should be) and no pulsation observed. YMMV :mrgreen:
 
IIRC the rotors are NOT triple plated (copper/nickle/chrome). If they are this may not work completely.
Hydrochloric acid eats chrome... Hardware store muratic acid is 28% hydrochloric acid.

1. Shallow plastic pan
2. Outside
3. Clean or sand blast any paint off.
4. Put in the pan of acid.
5. it will bubble tiny bubbles and turn yellowish as it works.
6. The chrome is all gone when it no longer showers of sparks in a sand blaster.

This process has hazards and should not be attempted by children (or the mentally deficient) as they may hurt themselves.
I am doing one now and will let you know how it works...so far... so good.
 
Great thanks guys,

Im gunna price up getting the chrome removed as I have to get a couple other pieces chromed anyway, then I will probably finish the disks
by hand. They have plenty of meat in them just been sitting a long time
 
front rotor after a few hours different shade of gray around center that was still chrome center 80% was very similar to above posted pix by charger
http://atlanticgreen.com/images/DSCF0060.jpg
a little bit of sand blasting
http://atlanticgreen.com/images/rotorfront.jpg
rear rotor note uncleaned painted area
http://atlanticgreen.com/images/DSCF0059.jpg
painted area after blast residual chrome
http://atlanticgreen.com/images/rotorback.jpg
Actually you could deplate only the wear area by thoroughly painting the front and back centers which would then be protected.

If you bring your rotors to a chrome shop they should have "heavy duty" hydrochloric that would blow the chrome off in 10 minutes.
 
Thanks for the Pic Follow up,

How long did you leave in the acid? is it just straight Hydrochloric acid?

Cheers
 
as posted above:
"Hardware store muratic acid is 28% hydrochloric acid" I would be quite scared of 100% hydrochloric.
I used what I had left, about 3/4 gallon...I will re-dip to finish the paint protected center.
My rotor had less chrome than yours. You can see the faint 1/2 to 3/4" ring around the center and 1/8 to 1/4" ring on the outer edge.
Next one I will protect the center and deplate only the brake surface.

I pulled them out around 6 PM so maybe 6 hours...maybe more
 
Taxi companies have those little machines that crawl around the disk and grind it flat and even.
Seen it at work in Brisbane, sure to be one on the GoldCoast.

Bike disks have very little thickness can be removed before they are too thin to be legal thickness.
And with that wear pattern , you'd want to be sure its not warped...
 
Bob Stephenson of Spondon ground some LeMans discs for me. When I asked about how thin to go, he got some new Japanese discs and we compared them. Mine were still about 1/3 thicker again after the regrind, so safe as then...
 
I took my MK3 discs to the local "engine reconditioner" and he surface ground them for about $60... In having them ground on a table you can be sure the individual sides of the disc a parralell to each other... Im a bit suss about doing them in a lathe ..... unless both side are done together ....

I wouldnt bother with the snake oil remedies with the surface fininsh, let alone the enviromental hazards you will face... They are of course "brakes" remember, so they need to be done properly..
 
Disk thickness - most (motorcycle) disks that have thickness or wear limits 'printed' on them seem to allow 0.7 mm wear.
Thats 14 thou each side, from new to worn out..

Cast iron disks need to be kept fairly thick, or being brittle can come into it.
Stainless disks less so, since they are capable of bending under provocation, it seems.
(Not that that would be good !).

It was discussed here previously that Nortons seem not to have published any specs on Norton disks re thickness.
Andover Norton were going to look into this, but nothing has appeared yet. (?).
 
Just as a generalisation http://www.dba.com.au/ are worth checking out since they make most of the new replacement brake rotors for these type of motorcycles.
Ducati 750 GT front rotors sell for a premium yet I picked up a brand new front for less than half of what people will pay for a used OEM item when they come up , a 900SS rear and complete set of three for my 1981 900SD.
Maybe they are the ones doing the Norton rotors for those with ones beyond service limits.

I would not compare an iron rotor with a SS version as far as wear limits personally.
 
Hi Charger, I got 2 discs ground and drilled by gfh150 in the US off eBay. Cost $139 each look sensational.
 
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