Setting run-out; on car brake lathe

[Tony01013]

Hey everybody,I’m taking Auto Tech at my local community college and one of my labs right now is using an on car brake lathe. This is an older model machine that you have to manually compensate for run out by adjusting screws on the motor hub. Does anybody have any experience with these type of brake lathes? I’m going to ask the instructor, but I would like to know if anybody has any tips or tricks to set the run-out. It seems like I’m having trouble bringing the runout into spec. I either adjust it too far one way, then too far the other way and I’m chasing it back and forth.

Topic

[Lonestartech]

There are some pretty decent videos on youtube showing you how to use the different brake lathes

[BigC]

Hi Tony01013,

I remember using some older brake lathes at community college. We would adjust the cutting tip on either side until it would make audible contact with either side of the rotor, or inside of hub. Then the cutting tip would be adjust 0.002″ more towards and rotor/hub and proceed with the first pass of shavings. Afterwards, the cutting tip(s) were continually moved towards the cutting surface (usually 0.002 – 0.005″) until then entire rotor or hub surface was freshly cleaned. Double check with your instructor on the minimum thickness setting needed for the cutting tip(s).

Make sure that you are using some type of dampener on the spinning hub or rotor. There should be an adjustable belt of some type that straps around the rotor or hub. This helps reduce any vibrational impact on the rotor due to the turning of the rotor by the cutting tip. After the rotor or drum is completely turned, gently “rough-up” the surface that has just been turned with sand paper, putting a non-directional pattern on the shiny metal.

Good luck. Brought back some good memories. Keep us posted.

[Gen3]

Im not an auto tech and dont have experience with brake lathes, but could the rotor be loose on the hub? (does this sound like a holiday inn TV commercial?) Anyway if you are chasing it, and you cant get the rotor to “zero” to the cutting tips it sounds like the rotor is rocking (not sitting flat on the hub) or the arbor (or whatever you call the thing that holds the cutting tips) is moving relative to the rotor. Maybe the hub has a bad bearing? I assume there is a dial indicator mounted on the brake lathe and the indicator tip is touching the rotor? I saw one of these types of machines set up before. I would guess it was “donated” to the college. It looked like a major PITA to set up. It was used for the infamous “captive rotors” seen in some of Eric’s videos.

[EricTheCarGuy]

I’ve actually been privilaged enough to use the automatic machines so I’ve never had to set it up for runout manualy, in fact I don’t know of a shop out there that uses a manual one so I really don’t see the point of teaching how to use one in school but that’s just me.

[Tony01013]

Hey,
Thanx for everybody’s input. I finally figured it out, it’s just very touchy. But yeah Eric, you are right. Nobody uses the manual on the car brake lathe. I think they just want to teach us the concept of run-out. I talked to my instructor about it and everybody has the model where it automatically sets the run-out.

[dreamer2355]

I think its a good idea learning using manual methods over automatic as you get a better understanding of what is going on C8-)

[EricTheCarGuy]

There is one tip that I can impart however and that is if it’s not lining up try dismounting it, rotating it 90

[Author]

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