brake disk grinding

Hello Access Norton, I am a new member here and am currently restoring my mk3 Commando. I am going to have the brake disks reground, but I cant find any specs ie. stock disk thickness, and minimum thickness. My disk measures 0.267-0.275. Any help would be appreciated, thanks.

Welcome. That subject has been discussed here previously, a few times.
Initially we couldn't find any specs on the disk, but someone eventually located a minimum thickness quoted.
I think it was 0.250" but can't readily find that link to that reference.

There is very little leeway on other markers disks between brand new and worn out,
0.7 mm being commonly quoted. (approx 28 thou).
Norton disks have a thin layer of decorative chrome applied to them, (to stop them rusting in the showroom ?),
and until this is removed or worn off, the braking is less than ideal.
The cast iron disk needs regular use to keep the rust at bay...
hopethishelps.

moond850 said:

My disk measures 0.267-0.275.

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From the banter in the recent past, there is no minimum spec. Based on your supplied dimensions, it sounds like you're working with original thickness discs. Is there any chrome left behind? that would be a dead giveaway that they wouldn't have been ground before. Also, get them Blanchard ground if possible. http://www.accessnorton.com/disc-brake-rebuild-surface-t19529.html

Welcome to the forum!

Nathan

Nater_Potater said:

moond850 said:

My disk measures 0.267-0.275.

Click to expand...

From the banter in the recent past, there is no minimum spec. Based on your supplied dimensions, it sounds like you're working with original thickness discs. Is there any chrome left behind? that would be a dead giveaway that they wouldn't have been ground before. Also, get them Blanchard ground if possible. http://www.accessnorton.com/disc-brake-rebuild-surface-t19529.html

Welcome to the forum!

Nathan

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disc-brake-rebuild-surface-t19529.html#p250195

Thank you all ! My disks still have some chrome remaining, but mostly gone. I think this forum is a great place to share ideas. I will be here a lot.

Disc Brake Rebuilders (DBR) is great for Blanchard grinding (and drilling if desired)

Don't take your Norton brake disc to the local car parts/machine shop or the muffler/brake shop down the street!
They won't be able to mount them sufficiently to turn them flat and parallel. One shop tried to grind them on their flywheel grinder and they turned out a mess.
I found a machine shop that does precision grinding to military specs close to my home. The rotors came out flat and both sides in parallel to some ungodly infinite number of zero's. They were recommended to me by some hot rod guys who build their own sprint cars, so asked around and find the right machinist.
Ride On
Dave

Does old britts still do the blanchard? Might be worth a call. I hear they do good work.

http://www.ebay.com/itm/NORTON-BRAKE-RO ... 35&vxp=mtr

This guy does great work. My disc is as the picture shows. Getting the chrome off and using Ferodo pads makes a difference. I also had my master cylinder sleeved to 13mm so the braking has gone from non existent to acceptable.

I didn't use Ebay but have a phone number somewhere for him. You can find it by Googling machine shops at the IL town he's in.

Make sure you tell him MKIII front so the drilled holes, if you have it drilled with a sweep patern, will sweep in the correct direction.

Pretty sure Fred stopped doing rotor grinding.

This guy did mine and many other Norton rotors:
http://www.ebay.com/usr/ghf150?_trksid=p2047675.l2559

You can buy a new AN rotor drilled and lightened by OB . They sometimes have exchange but better call them and ask.

The guy in Caseyville, IL is Gary Hollowich. He has done a number of disc's for me. He also does them for a number of bike shops around the country. He can also drill them if you want.

boz said:

The guy in Caseyville, IL is Gary Hollowich. He has done a number of disc's for me. He also does them for a number of bike shops around the country. He can also drill them if you want.

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'Zactly! I have his number at home but I'm sure you can google it. His work is beautiful. I also sent him a Bonneville disc and it came out just as nice.

tomspro said:

This guy did mine and many other Norton rotors:
http://www.ebay.com/usr/ghf150?_trksid=p2047675.l2559

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I was charged $50 USD last year by a local who obviously knew what he was doing (local biker/hot rod guy who owns a machine shop), but, for an extra $15, I'd just as soon my rotor came back to me already painted. 'Looks like Gary at fleabay would be the way to go. Those are some pretty discs he shows! That, and consider getting the lightening holes added, as that's one heavy chunk of cast iron hanging off the front end.

Nathan

Rohan states that Norton used DECORATIVE chrome on the discs to stop them rusting.......I thought it was supposed to be hard chrome and because it gives a 10 to 15 % reduction in the Coefficient of friction that is why Norton supplied two friction materials on the pads..2424F a high / high friction material and 2430 a medium / low friction material. Of course it could be that the letter from Ferodo (dated 9 Nov 1987) giving me this information about different friction materials was wrong....... it also srtated that these materials had been superseded by another material - 2453.
I am certain the manuals told owners to use the CORRECT pads for their model. Wonder how many owners ran around with the wrong pads fitted and then moaned about the brake not working correctly??
Incidentally when I had half a dozen new chromed discs dechromed the company doing it (who specialise in hard chroming) suggested that the discs had simply gone past the front door of the chroming factory and not actually made it inside as the quality was CRAP.

J. M. Leadbeater said:

...I thought it was supposed to be hard chrome and because it gives a 10 to 15 % reduction in the Coefficient of friction that is why Norton supplied two friction materials on the pads..2424F a high / high friction material and 2430 a medium / low friction material.
I am certain the manuals told owners to use the CORRECT pads for their model. Wonder how many owners ran around with the wrong pads fitted and then moaned about the brake not working correctly??

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I wouldn't be surprised. However, mine never was that great from the factory, and I would have hoped the correct pad/chrome combo would have been done then. I can tell you that, as the chrome wore off, the brake would grip on the bald patch, then act like the lever was released as the chrome rolled through. It made for interesting low-speed turns in the parking lots.

Nathan