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Thread: Rotors only on a brake lathe?
05-07-2009, 04:18 PM #1
Rotors only on a brake lathe?
Not knowing much about lathes, I asked the lathe operator at my previous place of employment about turning rotors on an engine lathe (not that I wanted him to do mine, just curious). He said that the old timer, who taught him, said not to turn rotors on anything but a brake lathe. What's the difference? I worked in a garage when I was a teen, and I saw how rotors were turned. The only real difference I saw was that they put a rubber strap around the outside to keep the squealing down, and that they had mounting cones for automatic centering. Other than the swing being an issue, why couldn't a rotor be turned on an engine lathe?
05-07-2009, 04:34 PM #2
rotors on engine lathe
I feel the issue is it is hard to cut both sides of the rotor in same set up on most lathes . distortion from chuck is an issue. and getting them to end up true to there axis . Auto mfgs spend an awful lot attention to this stuff . any error ends up being felt in the pedal. as far as i am concerned most auto rotors are available pretty cheap often not much over turning charge . The brake lathe i have seen have not done justice to the job. I have run a number of them in my younger years. Take rotor lathe turn a disc the carefully turn it on the tooling 180 degrees re clamp it and measure run out . Try this at the tire shop with there balancer watch the numbers . many new cars do not have very much material to remove before below fed spec . truck rotors often times get pricey and make sense to turn .
05-07-2009, 04:37 PM #3
yes you can trun them on a lathe. if you take the time to make a spud to bolt them to. it is all in the setup. a brake lathe is just a lathe it just has the setup parts to do brakes.
05-07-2009, 04:39 PM #4
I did it on my F150 rotors last fall. It is very hard to get both sides but it can be done with a LOT of effort. I probably wouldn't do it again. -Mike
05-07-2009, 04:52 PM #5
I do mine in a regular lathe, I use a boring bar in an Aloris toolpost to reach around the other side. I put a long tool bit in a 45 degree bar backwards and it works fine. I usually just machine a hub to mount the rotor on and use a long piece of 3/4" all thread thru the spindle to hold the rotor on the fixture. It would be easier doing it on a brake lathe, but I just have a habit of doing everything myself.
05-07-2009, 04:53 PM #6
Ah! Rotors = Brake discs (you say tomayto, I say tomato...)
Do drum brakes have 'drums' on your side of the pond ?
(I'm just fascinated by how our 'common' language differs)
05-07-2009, 04:57 PM #7
Our drum brakes do have drums.
05-07-2009, 05:21 PM #8
I do it if I have to but it's cheaper to have a brake shop do it. The manufacturers want you to hold them the same way they are mounted on the vehicle, by the bearing races. I've made an arbor or 2 to resemble that spindle of a brake lathe and mounted them in the engine lathe, holding the drums/rotors with tapered cones just like on the brake lathe. I had to turn the magnet surface of 6 drums of a trailer with electric brakes and no one would touch them. So they went in the engine lathe on the arbor and I cut them just fine thanks, work fine on the trailer.
05-11-2009, 08:19 PM #9
When disks first started replacing drums, and garages were not set up to reface them I did some in a 14" lathe. I found that it was necessary to cut BOTH sides at the same time. Made up a plate with two brazed carbide tools mounted on either side of a slot that was about 1/4" wider than the rotor. Distance between tool bits was "eyeballed" to take enough off to clean up the rotor, which was mounted on an arbor with a pair of cones that picked up the bearing races in the hub. Trying to do one side at a time was a disaster, but cutting both at once gave a parallel, true surface.
05-11-2009, 08:43 PM #10
Herb, that's the correct way to do it.
here's a few shots of a facing tool for rotors. Rusty from my lack of care.
05-11-2009, 11:34 PM #11
I bought my 13" specifically to turn brake rotors on karts. I understood that I had to hold the rotors by their mounts. I didn't know that I had to turn them on both faces at one time. Is there a place I can find that tool holder or get plans for one?
05-12-2009, 01:17 PM #12
05-13-2009, 05:30 AM #13
Was going to do the rotors on my wifes car on my lathe but decided to give the wreckers a try as the car was a very high volume model. Found a practically brand new car with zero body or frame damage. Figured it must have been some kind of engine problems. The rotors were barely worn in. Both rotors $40. Indicated them on my lathe and the runout was in tenths. Those rotors were still on the car when I gave it away years later.
05-13-2009, 06:46 AM #14
I've done lots of rotors machining them ONE SIDE AT A TIME, and they turned out fine. Anyone who says they can't do it that way, simply doesn't know how to do machine work. It's not rocket science, you are just machining a piece of cast iron. If you have the rotor mounted properly on the lathe, it makes no difference if you machine one side or both. Sure it's easier if you have a way to do both sides at once, but the point here was the ability to turn rotors on a regular lathe. I know of quite a few people who sent rotors out to an auto shop and had them screwed up.
05-13-2009, 07:18 AM #15
New rotors for my F150 front, $31/ea., and no hard spots. Not worth facing.
05-13-2009, 07:36 AM #16
Well, try $150 for a Ford 450.....
05-13-2009, 09:29 AM #17
Crappy brake lathes
I just had to weight in here. For some years I have tried to keep the local Less Schwab tire stores brake lathes turning true. Problem is all the brake lathes I have seen are really just piles of junk. Terrible slide ways and tool holders. The biggest problem is the damn spindle. If you look at one its just a threaded rod that is made of soft material. You slide sloppy fit cones onto the threads to supposedly center the brake rotor or drum. These cones and other tools used on these machines are made of basically cold roll steel and usually just tossed in a box or a heap under the machine. I have never seen one of these machine you see at your local tire store that is worth a darn. I have seen rotors that were warped come off one of these machine worse than when it whet on. I know I will ketch some flak over this but that is my take on it. I have always done a far better job of turning a drum or rotor in a engine lathe than one of these brake lathes will ever do. Then it does not take much skill to run one and most of these guys have never seen an engine lathe or have a clue as to how you actually cut metal. Funny thing is when they are working on someones race car you can guess who they bring the parts to to get a good job. Yep old Turk Mfg.
Nasty old Turk
05-13-2009, 09:49 AM #18
That's probably a large part of the move to on-car turning of rotors. With on-car turning at least it will be true until it is removed one time.
05-13-2009, 10:25 AM #19
i did my 1977 corvette rear discs , they have drums on the the back side and i cut the face for the lug nuts at the same time and flipped it and did the other side. very smooth drive. worth doing yourself.
05-13-2009, 10:51 AM #20
The above made me curious so I Googled Turk Mfg.
Great looking web site, and the photos make me want to work there.
The history of the company should give encouragement to all of you guys recently thrown to the wolves.
Good for you, Dennis.