Drilling a Norton front brake disc

After attending the INOA Feather River Rally in Quincy, CA, where I saw a lot of VERY nice Nortons and a lot of them with drilled frond brake discs, I decided that I just had to drill mine. It turned out to be easy to do, as the thing is cast iron and easy to drill without any kind of a special bit. I marked it out in 30 degree increments using blue DYKEM and a scribe on the disc and made an "index mark" out of a piece of aluminum scrap to clamp down on my milling machine table so I would be able to accurately rotate the disc in order to get the holes all in the right spots. My milling machine's table is not big enough to just clamp the Norton disc down and have at it using the DRO for accurately placing the holes. I intend to remove the disc in the (hopefully) near future and do a little painting to spruce it up a little and to keep it from maybe rusting.

Anyway, it was easy to do, came out looking pretty decent and was WAAAYY cheaper than just popping for a "commercial" one. NOTE: It appears to me (so far) that if you want to view the 2nd through 5th pictures, you have to click on the link. I will see if I can figure out how to get the pictures to appear without having to go through that!! (I'm a computer dinosaur!)

[Image codes corrected - L.A.B.]



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If anyone wants to do this and has questions, please ask....my email is doninreno@sbcglobal.net.

Welcome to the forum. Nice to have machine tools...

was WAAAYY cheaper than just popping for a "commercial" one


grandpaul » Mon Jul 18, 2016 9:11 am

Welcome to the forum. Nice to have machine tools...


This is the sticking point for so many. Once you have the big kid tools a lot
of small parts and even large parts are a lot cheaper.
But you need access to the tools or tools of your own.
What is the investment to get there? Have room for them? etc etc

Thanks for the kind words.

Yeah...about the time I retired about 8 years ago (was NOT a machinist or a welder.....was in the aviation business), I bought some "toys" I figured I would need and then went to the local tech college to learn a little about how to do machine work, TIG, MIG and stick weld and so forth. I really enjoy being able to make stuff and am ALWAYS learning new things about how to use/better use my tools. My skills are expanding every day ....it is fun to dream something up, figure out how to make/do it and then do it!

I am lucky in that I have a buddy that wanted a TIG welder, so he paid for half of the machine and the gas, supplies, etc. I would guess that I have about $9500.00 invested in various tools (have a box for "inch" tools, a box for Metric tools and a few drawers reserved for Whitworth with one drawer for "Custom made" :lol: tools) and machines since I retired. Also, I would guess that I have saved at least half of that amount (I KNOW the TIG welder has more than paid for itself) by making my own whatevers......not to mention having the luxury of getting it to be exactly what I want even if I have to modify it a little after the first try AND I get it like RIGHT NOW.....don't have to hope that whoever I would ask to make it does it right and also I don't have to wait weeks or months for a "whatever" to get made/built. I have a three car garage/shop where all of this junk lives (my wife, for some strange reason thinks she ought to be able to park her car in there! Go figure!! I just chalk that up to "life".)

Your pattern looks to be right on. Mine is modeled from the Old Britts pattern.
You just slip over the hub, tape it in place and transfer the punches. This material is possibly the easiest of all to drill, other than wood.

Did you chamfer the holes on both sides? I use a 1/2 inch counter sink bit to just knock off the sharp edges. I was told this helps to prevent the cracking that some have experienced with the Norton discs.

Ron....I used a hand chamfering tool to just knock off the hard/sharp edges around the drilled holes.....i wanted to be sure that there were no burrs sticking up above the friction surface of the disc. If you look carefully at my pics you can see the slight chamfer on each hole. I did my best to make them all the same while doing it by hand by hand, counting number of twists and attempting to use the same amount of pressure on each while maintaining the de-burr tool as perpendicular as possible. I suppose that if I used some time to set the milling machine up correctly, I could have cut them all exactly the same down to the .001" or so, but didn't feel that amount of accuracy was called for.

Nice looking work.

The reason mine went out was to have the chrome ground off AND drilled. The chrome wore off unevenly making for a pulsing brake. I found better braking on bare cast iron. That, plus sleeving the master cylinder to 13mm made the brakes acceptable.

Nice work Don. I have this on my bike too. It cured my squeaky pads issue and improved braking in the wet.

While I think the drilled rotors look the business ( modern ) .... is there a functional reason for drilling them .... both my Italian bikes have Swiss cheese rotors and I have never been certain why ... I have upgraded my Commando front brake with the CNW master and SS line plus EBC platinum pads and it stops way better than original .... would I notice any more improvement with a drilled rotor ?
Craig

Id look to the weight savings . Not so sure drilling the working system is all that effective for iron rotors.
Since I installed a sleeved master at the same time as the drilled rotor I cannot say the drilling was or
was not really effective.

Craig said:

While I think the drilled rotors look the business ( modern ) .... is there a functional reason for drilling them ....

Click to expand...

http://auto.howstuffworks.com/auto-part ... otors1.htm

https://www.apracing.com/products/race_ ... discs.aspx

Thanks Les .... all very interesting , however for what I use my Commando for , think I will leave the rotor well enough alone .... works great as is ....
Craig

JimNH said:

Nice looking work.

The reason mine went out was to have the chrome ground off AND drilled. The chrome wore off unevenly making for a pulsing brake. I found better braking on bare cast iron. That, plus sleeving the master cylinder to 13mm made the brakes acceptable.

Click to expand...

Jim,

I am kind of curious to find out how much a place that does drilling charges nowdays. I don't want to pry, but can you give me a ball park number? I put a (IIRC) a 13mm Brembo master cylinder on mine and the brakes work REALLY nicely now. Two fingers are almost too much and the brake is nice and progressive and not "light switchy" at all. I turned the finish of off mine years ago and having the iron brake surface made a great improvement in braking power. In Reno, the humidity is so low that I have NO problem with rust/corrosion, but I'm guessing that if the bike lives in either a salt air or very humid environment, that just may be an issue.

Don J
Reno, NV