View Full Version : Using brake disc cast iron in the shop.

02-16-2008, 12:23 PM
In the auto dealer I work for, we fill up a 4' x 4' x 4' box with used brake discs and misc. iron & steel scrap every couple of months. It ends up at the local scrap yard and we feed everyone a "scrap lunch" in the dealer occasionally with the money made. I'm sure the iron comes back after a while as H/F lathes & mills.
I picked out a few of the larger solid ones and cut them up on the bandsaw to put in my stockpile of metal. It's a little under a half-inch thick and machines beautifully. I reckon you could say they're work hardened & heat-treated what with all the heat cycles they go through in a few years of hard use. The pieces can be squared up and used to make model steam engine frames, tooling brackets, repair material for machines, etc.

In these days of ever-increasing crime, a feller could wear one as a hat and learn to sling it at burglars like 'Oddjob' did in the Bond movie Goldfinger.


I used 2 of the big vented ones and the outer rim of a solid one to make a counterweight for my X-3. It didn't come with a gas strut and would wear out my shoulder cranking the head up & down until I made the "crane" with compound pulleys. It spins up & down with one finger now.


Recently, I discovered the vent holes make a handy place to store often used tools & widgets.

02-16-2008, 03:10 PM
I've seen hard spots in those that unobtaniun carbide world bounce off of and across the street. I wouldn't believe that anybody could band saw one if I hadn't seen it. I like them for workstand and lamp stand bases. Like your crane.

02-16-2008, 03:49 PM
GK the ones I cut up were from Land Rover vehicles....dunno if they use a softer/different/better iron than other brands but there was no evidence of any hard spots whatsoever. My little 4x6 H/F saw with a H/F bimetal blade cut right through 'em like buttah. The ones hanging on my counterweight system are from a Jag and they milled & drilled very smoothly with regular old HSS very nicely.

You make a good point though! Sometimes I charge into something new not knowing any better. I guess I shoulda put a "YMMV" at the end of my post.:)

02-16-2008, 03:59 PM
I've found that ff they're just worn down they seem to turn pretty easily, but warped ones seem to be the ones with inclusions because you always hit hard spots.

Never thought of brake disks for material other than stands etc, Did make a faceplate for my first big lathe out of the flywheel for a 300-6 ford, worked great. But I actually use a LOT of car parts in projects, one of my normal routines is to run down to the local u-wrench-it with tape measure and check the brackets for a few different cars when I have a project in mind. Often find some that are almost perfect minor tweaks are all that's needed.


02-16-2008, 04:00 PM
among my many tools are two brake lathes that get a lot of use. I have never yet seen hard spots on rotors or drums. Flywheels on the other hand are always full of hard spots and I have to grind them. I made a adapter for my horizontal mill and put my four jaw chuck there and mount a grinder on the table. Don't like dry grinding in my shop so cover everything up. Also the setup makes a very large lathe for stuff that won't go in my 10" SB. Peter

02-16-2008, 04:08 PM
Are all brake discs & drums cast iron. I have found some will crack more readily than others when welded if a 6013 rod is used, have been able to weld
them OK using a 7016 (LH) rod although I would be carefull about using them
where the welded joint was to be under load. Ford Falcon(early 70s) drums
appear to weld better than others that I've used.
Have not tried maching them.

02-16-2008, 04:14 PM
Looks like a good cheap source for pieces of iron.

Another one I just tried are some exercise weights. The kind that have machined surfaces. They are a bit porous, but not nearly as bad the ones that are used as-cast.

02-18-2008, 09:14 PM
Called my old machinist and he verified your diagnosis that I'm nuts. He never remembered hard spots in DISKS, just drums and flywheels. Must have been drums I remembered. My wifes car, after trying to turn them they made me think of the pattern is ostridge hide boots. Speckeled with high spots that the cutter just pushed away from. I stand corrected.

02-18-2008, 09:27 PM
So why am I the only one who runs into hard brake roters?


02-18-2008, 10:06 PM
I had no trouble machining brake drums and disks.

I just pick them up at random from the scrap bin from the guy who services my car.

I wanted to try turning on the mill to see how I would go on stuff in excess of the 10" capacity of my lathe.

Pics follow.

This is the result of mounting a multi-tooth positive rake TC facing cutter where I could not wind the hand-wheel on my 90:1 rotary table fast enough (surface finish was better before the surface rust got to it - 6 months later):

'nuther view:

The "other" side ('scuse the surface rust here too):

I used it for tramming my mill (quick pic/"demo" here - needs cleaning):

I was very pleased at just how flat and parallel the opposite sides are - within 0.0002" actually - might have been just holding/twisting my face right on the day!

If I'd had time at the time I was going to use my boring head to "turn" the internal diameter and an end-mill to "turn" the outer diameter.

I would have probably used TC to "break" and "get under" the "as-cast" surfaces and then HSS.

That cast iron? - what-ever it was, was a dream to machine.

So, based on my experience thus far, I would have no hesitation in using it again.

Next time I will try welding it - MIG and brazing, and probably "stick as well - to see how it goes.

Links to the TC cutter are at:


02-18-2008, 10:08 PM
It's all to do with the driver. Anyone who rides the brakes instead of gearing down on a long grade will have their drums and rotors develop hard surface spots. My customers all seem to be good drivers. Clutches on the other hand all have hard spots. Even our race car rotors machined with no problem.

02-18-2008, 10:10 PM
Next time I will try welding it - MIG and brazing, and probably "stick as well - to see how it goes.

I posted some pictures of MIG brazing disc brakes awhile back -- it was uneventful.

Like any cast iron, conventional (non-brazing) MIG and TIG need nickel wire to get good adhesion, and you have to pre- and post-heat it or you'll hear the infamous "PING." :)