Thread: Turning inside of cast iron brake drums

Got 'rejected' by a Chevy dealer when getting a brake job done on my Suburban. Bought it used, and rear discs needed attention bad -- they had large areas of flaked up rust on the braking surface. Dealer says they couldn't be turned, and would be too small when they were done (gave me the spec as their defense.) Ordering them would be 3 weeks, paid in advance (!) due to GM bankruptcy at the time, and the fact that it was a QuadraSteer truck. Had 'em put it back together, brought it home, and took it apart again. Easily enough meat to do it, but my lathe tops out at 13". Mill and rotary table made quick work of it, though. In a few years, I'll order up replacements a few months prior to when I'll need them, and take a light cut on these to see if they can be the backups for the rest of the life of the truck.

The (new) cost of the discs from the dealer nearly equaled the cost of the mill.

Chip

I live in Hartford, Ct. not exactly in the sticks. I was doing a brake job on my 1960 Mercedes Unimog 404 that has drum brakes on all four corners. Two of the drums were like new and the two others looked Ok with just minor scoring. But why not do it right and have them turned. I spent over two hours calling around and either I got the reply we dont turn them any longer just buy new ones or what do you mean by turning a brake drum? Finally found a shop that said they do truck drums. Dropped them off and got a call two days latter that they did not have a fixture large enough for the center hole but would have their machinist make one up. Two weeks latter I picked up the drums not done but with all kinds of apologies on their part. I did them in two hours on my lathe. Sometimes it is just easier to do it yourself and I find that more and more these days. And that is the reason I have a home shop!

Which is why I have a shop full of tools I rarely use - brake lathe, tire changer, balancer, strut compressor etc.
It's worth it to not have to rely on morons to get routine tasks done.

Thanks for the replies everyone. I didn't get any more time this week to try any of the suggestions.

Originally Posted by Limy Sami

A thought, are these your land rover drums?......if so, watch the maximum diameter and check for cracks, also the centre location hole is not alway accurate.

Yes they are Land Rover drums. The one I tried to di I held on the outside of the internal chuck jaws and it was running effectively true as far as I could see.

They sell new ones online for £11.50, so I see what some posters are saying about it not being worth it. Still, if I get time I will give it a go.

Originally Posted by Chip Chester

Got 'rejected' by a Chevy dealer when getting a brake job done on my Suburban. Bought it used, and rear discs needed attention bad -- they had large areas of flaked up rust on the braking surface. Dealer says they couldn't be turned, and would be too small when they were done (gave me the spec as their defense.) Ordering them would be 3 weeks, paid in advance (!) due to GM bankruptcy at the time, and the fact that it was a QuadraSteer truck. Had 'em put it back together, brought it home, and took it apart again. Easily enough meat to do it, but my lathe tops out at 13". Mill and rotary table made quick work of it, though. In a few years, I'll order up replacements a few months prior to when I'll need them, and take a light cut on these to see if they can be the backups for the rest of the life of the truck.

The (new) cost of the discs from the dealer nearly equaled the cost of the mill.

Chip

My 2004 Silverado did about the same thing maybe. Kind of a wierd deal in my experience with disk breaks. A ring of rust started to build up at the largest part of the dia, it apparently worked inward, eating the pads in the process. I was dead broke at the time so as a "get by" I turned them on the bro in laws Hendey, and put cheap Auto Zone lifetime pads all around. The truck had around 60k then, has 80k now and they still look good. About the same time an inlaw had a GM car that was doing about the same thing, we just put new rotors on that one for about $20 a corner.

I'm not sure if this is all due to the "new" non asbestos brake linings they were forced into using ?? Since disk breaks became common I never have seen that pattern of a ring of built up rust at the largest die of the disk before. But then "back then" we never saw generally 60k or more on the factory pads either :-). Hell many cars at 80k the auto trans was poop.

Bill

Originally Posted by Webley91

They sell new ones online for £11.50, so I see what some posters are saying about it not being worth it. Still, if I get time I will give it a go.

Note that new drums almost always need to be turned, unlike rotors. So you aren't out of the woods on that yet

Originally Posted by Webley91

Thanks for the replies everyone. I didn't get any more time this week to try any of the suggestions.


Yes they are Land Rover drums. The one I tried to di I held on the outside of the internal chuck jaws and it was running effectively true as far as I could see.

They sell new ones online for £11.50, so I see what some posters are saying about it not being worth it. Still, if I get time I will give it a go.

I often find bolting them to a face plate easier and quicker to check for truth,......... back in the early 70's I used to do 8wheel tipper drums (easy 80lbs each*) in batchs of 24 + on a DS&G 21'' they had to be bored out and liners fitted and we had a centre boss on a faceplate then slip a few bolts through the stud holes.

A shift of humping those bleeding things around manually on my tod, was a bloody hard days graft.

Originally Posted by Rex TX

It's worth it to not have to rely on morons to get routine tasks done.

I've turned rotors too big for my lathe by setting up a spare spindle on my mill table and spinning the rotor with a vee belt around the perimeter. These were too big for my lathe and high dollar or unobtainable vintage parts. I would rather not trust them to anyone else.

Originally Posted by strokersix

I've turned rotors too big for my lathe by setting up a spare spindle on my mill table and spinning the rotor with a vee belt around the perimeter. These were too big for my lathe and high dollar or unobtainable vintage parts. I would rather not trust them to anyone else.

I made this setur to turn some truck rear discs for a friend.It worked so well that I have since made 3 aaptors for different bolt patterns to do what ever I need. I did the brake drums for my electric brakes on my trailer. Worked great with some tarp straps wrapped around the drum. My lathe is a 16 " and I have trouble reaching around the back sit to get full travel on large rotors.I really like this since cleanup is easier and size is no problem.




Forgot to add that for brake drums you place the tool holder in front of the drum and feed table back to bore it out.to keep this on topic.lol

Also just like "seasoned" engine blocks, a rotor that has been through many heat/cool cycles, that does not have hard spots, and is resurfaced, may be far better than a new one.

I live in Kansas City MO. and I also called around town to see about rotors/drums being turned Advanced,O'Reilys,Napa dont perform that service anymore for they would rather sell. new. So I lucked into a AMCO brake lathe that had some early 80's computer on it that the mother board went out on from NAPA. Pulled the spindle out of it along with the turning tools, made some arbors for rotors/drums, chuck the spindle up in the lathe to make a poor mans brake lathe. No not as cool as a real brake lathe but it will do

And you really need to verify any new parts that you want to use. I have a mechanic shop nearby to me that has a rotor and drum lathe and every new drum or rotor get a cleanup cut. He says many times that new rotors are not parallel side to side. And drums are not round. Of course, we all know what the source is now adays for $19.99 rotors.

I do my own on my 16" Hendy. There is usually an untouched surface somewhere where the pads or shoes don't touch to make a true set up off that surface.

Just to stray OT a little. I'm doing a set of cylinder heads right now and thought I'd treat them to new valves. Not racing, just a street engine. I checked the new valves for concentricity. Two of the intakes need to be turned and 6 of the exhaust needed to be fixed. Runout over .005 on the seats. The aceptable ones were all .001 or less.

Originally Posted by gas pumper

And you really need to verify any new parts that you want to use. I have a mechanic shop nearby to me that has a rotor and drum lathe and every new drum or rotor get a cleanup cut. He says many times that new rotors are not parallel side to side. And drums are not round. Of course, we all know what the source is now adays for $19.99 rotors.

I do my own on my 16" Hendy. There is usually an untouched surface somewhere where the pads or shoes don't touch to make a true set up off that surface.

Just to stray OT a little. I'm doing a set of cylinder heads right now and thought I'd treat them to new valves. Not racing, just a street engine. I checked the new valves for concentricity. Two of the intakes need to be turned and 6 of the exhaust needed to be fixed. Runout over .005 on the seats. The aceptable ones were all .001 or less.

There was (he still might be around) a guy in Delta, OH that was good with cyl heads, his check for proper seat concentricity was to drop the valve straight into the guide, if everything was right he got a nice "bounce" back up, makes sense to me :-). He had learned that from using spotting blue I suppose and comparing the bounce to the bluing. I had a set of heads that PAW did (outfit that Hot Rod buys engine kits from, or did anyway) the seats were WAY out to the guides, like .01 or more. I had owned the kit a few years without building it, and they blew me off claiming their records did not go back that far. Buddy had a set of heads that came from an auto parts store as "rebuilt" they used all oversize valves, and seats were way the hell out of concentric, compression readings on the cyl were all over the place with many under 100psi, engine ran like crap.

Thanks for the replies everyone. I did one of them today. Strip of rubber around the outside, held on with an adjustable belt that is usually meant for trousers (or "pants" as American members would say). Speed 35rpm, feed 0.1mm / rev.

It chattered a little for the first 1/2" or so of the cut, but this doesn't matter as the brake shoes don't touch this part.

i have turned drums on my 3-in-1 for 20 years using brazed carbide bars. interestingly i never had problems with vibrations.

http://i973.photobucket.com/albums/a...flansch002.jpg
http://i973.photobucket.com/albums/a...flansch003.jpg

The original drums will be better quality no doubt than pattern ones too, so its not as clear cut as everyone thinks regarding cost.
Point in question, I replaced my rear drums on my land rover 90 for the inspection as they were scored and efficiency was down with new shoes, but I figured they're only buttons to buy new while I was buying a bunch of other stuff.
The cheapo nasty britpart replacements warped within the first week and now Ive got brake judder to deal with. Ive still got the original drums to clean up and put back on and will have done the job twice.

Something nobody has mentioned is that the shoes should be re-arced to match the new drum diameters for proper full contact...

Originally Posted by Sean the Dog

Something nobody has mentioned is that the shoes should be re-arced to match the new drum diameters for proper full contact...

That is true. Aamco discontinued their shoe arcing attachment decades ago when all the asbestos lawsuits came out. I guess you could rig up a jig sort of like a ball turner.

1) go slow. Check the sfpm and then go slower.

2) get the right geometry tool. Too large a nose radius encourages the resonance

3) your tool will be stressed harder than you think. HSS is best avoided, the
best I've found for this application is cermets. You may find hard spots in there.

Horizontal milling machine does a great job running in 'lathe' mode.

If your drums have hard spots you can grind them with a tp grinder.The dealership I worked in back in the 60's leased all the county road patrol cars to to the county.They were 396 & 427 cuin BelAirs.Part of the police package was metallic brakes.G.M. would not install them from the factory although they did install the drums(They were ground finish) the shoes were in the trunk to be installed at the dealer.On a cold day they wouldn't stop until they warmed up and many newbie porters would run into the back fence when they went to bring them up for service.They had really good stopping power when hot though.Ammco drum lathes had a grinder for the metallic brake type drums.Make sure you don't use to coarse of feed when turning or else the shoes on the right side going forward will be pulled off the backing plate and make a noise when you release the brake as they slap the backing plate.I had a Quick-Way drum & rotor lathe that had an interrupted feed that eliminated that possibility.Hard spots go below the surface once they develop and although you may grind or machine them round again they are still there and will rise up after a few hot/cold cycles.The Chrysler composite drums seemed to be the worst about developing hard spots.Best to replace them if full of hard spots.
Randy