Disc Grinding

Found a shop that does blanchard grinding. What is minimum safe thickness disc can be ground to?

We've deeply discussed Norton rotor thickness factors to come to firm conclusion there is no standard published or agree'd on so you are on your own to find out for the rest of us but rest assured rusty or new chrome rotors can take a few grindings before any worry, unless impropper drilled of course. Maybe could get so thin the caliper pucsk push out of bores.

hobot said:

Maybe could get so thin the caliper pucsk push out of bores.

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I think that's where the real fear lies, as the rotors are plenty stout. As long as you didn't run your pucks down to where the metal backing plates began to show in the gap between the caliper and rotor, you should be fine.

Nathan

It was discussed before with a disk grinding thread that the maximum wear limit quoted on other disks was 28 thou (0.7 mm).
Its odd that Nortons didn't quote a minimum thickness.
Being cast iron, they could become a little fragile if made too thin ?

Other rotors are not Norton rotors and no one yet knows how thin they can get till rotor so thin its about see through which no one in right mind would attempt so failsafe there too. I've not measured how much caliper pucks can move together before escaping bores but will some day to know for sure but certainly over a couple mm's beyond full thickness of rotor. Main concern of thin rotor is heat distortion for racers or long long down hill braking and not wanting to use some engine drag in public use.

Blanchard grinding, the magnetic table will pull a warped disc flat ,and then spring back leaving a twisted disc. Plus the the rotational grind marks will cause rapid pad wear, The discs on trains have to be turned on a lathe ,or boring machine .

If the rotor is not warped, just poor friction surface would this magnetic flat table alert be a concern? You can search up the lathe turned rotors loss of grip effect d/t the machine lines to see if it might apply to Norton. On this note have there ever been reported examples of warped Norton rotors? I can imagine a racer boiling the brake fluid thermally distorting a factory rotor but think I'd cool back to flat to refinish surface. I can easier imagaine uneven surface wear that would be corrected by the criss/cross grinding. If surface could be made into a mmetal file surface that harshly wore brake pads I'd jump on it for the extra tire grip power and just replace pads every few years instead of decades of teeth gritting brake lever effort.

Arn't they just cheap enough to buy new?

hobot said:

If the rotor is not warped, just poor friction surface would this magnetic flat table alert be a concern? You can search up the lathe turned rotors loss of grip effect d/t the machine lines to see if it might apply to Norton. On this note have there ever been reported examples of warped Norton rotors? I can imagine a racer boiling the brake fluid thermally distorting a factory rotor but think I'd cool back to flat to refinish surface. I can easier imagaine uneven surface wear that would be corrected by the criss/cross grinding. If surface could be made into a mmetal file surface that harshly wore brake pads I'd jump on it for the extra tire grip power and just replace pads every few years instead of decades of teeth gritting brake lever effort.

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Buy new, are new one's being made available? New ones werre well chromed all over so still begs for resurfacing better. If going to Blanard grind I'd also condsider a water jetter to take almost 2 lb out of the unsprung spun inertial mass which is detectable to slow wheel faster w/o any other mods but its not a factory honest look. With my low level riding needs i've all the front brake I can ever use so wish good sucess for others improving looks and performance while sticking with factory basics. All brands of rotors through most the '70's were solid cast iron platters, though not looked to see if they were warp prone.

I tried years ago a grinding a disc on mag chuck grinder, you have offset the disc to the grinding wheel , but on the other side the flange does not support the disc very well a sits on a much smaller dia. Didn't have much luck . Any minute difference will cause pulses. You have a hard time to find anyone that regrinds automotive discs these days.

061885 £145 andover norton

$115 at Walridge during their sale. They are UK made cast iron repops. Not chromed.

Cast steel not cast iron. Blanchard grinding should be done on a cylindrical grinder so no mag chuck involved. There are various articles on discs that have been machined using a lathe. The concentric turned finish is very poor for friction until it has worn away. Blanchard grinding is the best for friction from the off.

Norton discs are cast iron - when you drill them, the drillings come off in little flakes,
a sure sign they are cast iron.

If you touch a grinder to them, the sparks are dull red - a sure sign of cast iron.
Steel throws a yellow spark.

I've seen a little machine for grinding discs crawl around a disc still fitted to a taxi.
They use them for getting their discs true all the time.
It left no visible grind marks, just a smooth matt clean surface.

There is not much margin between a new disc and a deeply grooved disc = worn out.
Be careful of getting them too thin....

Or your brake pucks may pop out of locator tab slots. Happened to me after long trip pulling into parking spot at home suddenly zero brake ,luckily super low speed ,feet down Flintstone style. I would only buy NEW rotor disc. Yes to Walridge brake sale goodness. :|

Torontonian this Maimian would like to understand why yours popped out? Many rotors have been re-surfaced w/o issue and the pucks have to have enough bore engagement to take up pad wear down to the base, so what can you teach us to avoid on this risk? What corrected yours?

Simply worn out pads. popped out pulling in at end of trip. Could'nt much freakin' believe it , pulled in to friend greeting then suddenly no brake. Flintstone stop. It was a long trip into the States then home to arrive at exact moment of puck-brake pop out failure worn out . Live good. :|

YIKES, Couldn't freaking believe it, LOL! and nod to another surviving Commando blood brother. I've complete instant loss and complete instant lock ups. I can't believe either Lockheed or Norton wouldn't prevented that predictable event. Who'd of thought but who'd forget now. This is a special alert for me Tronto as Peel's disc is maybe a 1/3 of factory rail road wheel so must check and maybe pad back of pads. Crap do I hate spikes of fear through the Joint and pensive hopping on something I worked on. Sends shivers down my spine being lazy dazy checking pads with rare flats or new tires. Another weird thing on Peel retaining the Lockheed caliper and bigger OD narrower wave rotor is pad extends past wavy rim by at least 1/4", so don't know if better to slice off excess pad or let it wear in to also grip the outer rim, hm being wavy, better thinking to water jet em, so another trip to friendly hi end shop with 2 story dinosaurs to digital age. These wavy rotors have aggressive mill pattern and are supposed to be used with metalic material or wears down fast but furious. I have little respect for brakes as tire limits my factory Lockheed, SV650 320mm dualy and Peel with restriction poked out, so if good as a decent Lockheed can be then quite good enough for me. I have only hand sanded my factory rotors and pads mostly to get deep rust or oil off but barely effects the base metal yet distinctly eases my brake concerns after. Maybe orbital sander would be the cat's meow on DIY up keep with nil worry to thin rotor just the pads. Hm what grit - 60? Ohh maybe could be laser etched and pull stoppie, if tire could take it.


Can someone slip a Lockheed caliper off and see how close a puck or pucks approach each other before popping out with fluid draining.

Worn out popped out thank god end of long U.S. trip basically end of ,with welcomes home, popped out brake pads as skidding in with luggage and girlfriend going "yay" didn't tell her about alarming Flintstone stop into home , just needed to answer messages n' pay rent etc. Girls love it all. BMW Boring predictable she said. I'm a lucky guy. Brakes.

Dang it man - these unpredicable cycle events could drive a fella to drinking and drugging to celebrate our survival or loss of those that didn't. Girls seem born knowing men are idiots with their hobbies and close calls so don't show up in Darwin's list nearly as often and when they do its too often going down with men they trusted to the end. I force myself to brake test my nerve each time leaving but know its only half fast way to prepare for the unknown. My Trixie caliper cap has fused to the caliper again and I've esculated heat and torque to point can't do it mounted on forks as whole cycle lifting to fall over so will have to remove to be handy to measure the puck escape distance. We are all here yet only d/t Grace or pure Luck or Karma.