Disk brake turning
Close
Login to Your Account
Page 1 of 3 123 LastLast
Results 1 to 20 of 46
  1. #1
    Join Date
    Oct 2012
    Country
    UNITED STATES
    State/Province
    Washington
    Posts
    194
    Post Thanks / Like
    Likes (Given)
    125
    Likes (Received)
    38

    Question Disk brake turning

    I need to help a buddy out by straightening up his disk brake rotors for his mini dragster. They are a odd size with a five hole mount pattern. In short not available any more. Dealer wants $378.00 ea to replace them. The rotors are next to new and have a maximum run out of less then .005". But are pitted and have rust bumps even after a glass bead spray.

    Who has the best procedure to do a simple turn on an engine lathe. Is grinding a solution? No local brake shops will touch them with no real reason given.

  2. #2
    Join Date
    Jan 2005
    Country
    CANADA
    State/Province
    Saskatchewan
    Posts
    9,655
    Post Thanks / Like
    Likes (Given)
    1192
    Likes (Received)
    3316

    Default

    They can be lathe turned. Isn't done much any more because the cost of new ones is typically so low it isn't worth the bother. I haven't done any for years now.

    They really should be turned on the bearings they run on for absolute true running. That's the main reason that they don't 'turn out' acceptable. All the crap and corrosion on the locating surfaces will cause some wobble, unless really scrupulously cleaned up.

    If the rotors have been dismounted already (should be marked for position on the same stud), then I've usually found it best to just indicate on the worn surface for the purpose of getting the face to run where it ran on the vehicle. If you try to 'correct' for some runout by indicating on some other surface, it sometimes doesn't work like you'd expect and the thing will wobble.

    Get both sides parallel. Perfect is good I usually just chuck on the rotor OD so as to not have any ringing issues. Turn it around to face the other side, that's when you take the extra care to get it set up to machine parallel sided. Set up as close as you can to perfect, Take a trial cut and measure the thickness at 4 spots at 90 degrees to each other. Adjust the position to get the thickness perfectly parallel (light taps with a hammer).

  3. Likes 9100 liked this post
  4. #3
    Join Date
    Oct 2005
    Country
    UNITED STATES
    State/Province
    Pennsylvania
    Posts
    10,598
    Post Thanks / Like
    Likes (Given)
    17619
    Likes (Received)
    5571

  5. #4
    Join Date
    Feb 2010
    Location
    ch
    Posts
    2,048
    Post Thanks / Like
    Likes (Given)
    187
    Likes (Received)
    269

    Default

    dont ovethink this. put it on the lathe and do it. be intelligent. doesnt matter if you flip them or not. oem spec is 0.05 mm or more. dont make them perfect, because they need some runout to get the pads off the rotors. be sure you register on the right surface.

  6. Likes MrWhoopee, Dave D liked this post
  7. #5
    Join Date
    Oct 2006
    Location
    Vancouver, B.C.
    Posts
    1,026
    Post Thanks / Like
    Likes (Given)
    84
    Likes (Received)
    174

    Default

    Disk rotors are often machined by cutting both faces at once but you can do one side at a time. Set up is fairly straight forward, vibration while machining is what is going to be the challenge.

    I guess this is firmly in the it has to be the best/look the best arena but from a practical perspective is this mainly cosmetic? The beauty of brake rotors is that they still work extremely well while pitted, grooved, have runout and while very, very hot. Any minor "rust bumps" would be long gone the first time you use the brakes.

    Dave

  8. Likes JohnEvans liked this post
  9. #6
    Join Date
    Jan 2005
    Country
    CANADA
    State/Province
    Saskatchewan
    Posts
    9,655
    Post Thanks / Like
    Likes (Given)
    1192
    Likes (Received)
    3316

    Default

    Quote Originally Posted by dian View Post
    dont ovethink this. put it on the lathe and do it. be intelligent. doesnt matter if you flip them or not. oem spec is 0.05 mm or more. dont make them perfect, because they need some runout to get the pads off the rotors. be sure you register on the right surface.
    Nobody likes to feel pulsating brakes. Parallelism is the requirement. As for getting the pads off the rotor, I'm sure that the small alignment errors when mounting the rotors on the hubs provides enough 'incidental lift' to accommodate that requirement, if it exists.

  10. Likes AlexO liked this post
  11. #7
    Join Date
    Sep 2004
    Location
    RSA
    Posts
    1,107
    Post Thanks / Like
    Likes (Given)
    394
    Likes (Received)
    278

    Default

    I did this many times and have yet to get it right. Barely usable. And I clocked the disk within a couple of microns. I had it done "on the car" and the result was 100%. I think this means something.

  12. #8
    Join Date
    Oct 2005
    Country
    UNITED STATES
    State/Province
    Pennsylvania
    Posts
    10,598
    Post Thanks / Like
    Likes (Given)
    17619
    Likes (Received)
    5571

    Default

    Quote Originally Posted by AlexO View Post
    I did this many times and have yet to get it right. Barely usable. And I clocked the disk within a couple of microns. I had it done "on the car" and the result was 100%. I think this means something.
    '99 dodge 2500, PIA to get the rotors off.

    $35 HF (gasp) cross slide vice, a $10 die grinder, an old
    1/4" motor mounted to a board with a C-clamp, a belt....
    Attached Thumbnails Attached Thumbnails rotor-machining-001.jpg   rotor-machining-002.jpg  

  13. Likes randyc, Dave D, JohnEvans, muckalee, AlexO and 3 others liked this post
  14. #9
    Join Date
    Jan 2012
    Location
    Midland, Texas
    Posts
    1,348
    Post Thanks / Like
    Likes (Given)
    382
    Likes (Received)
    685

    Default

    You don't mention what the problem is. If the brake pedal pulsates, the two sides of the disk are not parallel. If you get a general vibration, you have too much runout.

    Don't remove too much metal because you need it to dissipate heat, especially on a dragster.

  15. #10
    Join Date
    Sep 2002
    Location
    Riddells Creek,Victoria,Australia
    Posts
    451
    Post Thanks / Like
    Likes (Given)
    60
    Likes (Received)
    49

    Default

    Quote Originally Posted by digger doug View Post
    '99 dodge 2500, PIA to get the rotors off.

    $35 HF (gasp) cross slide vice, a $10 die grinder, an old
    1/4" motor mounted to a board with a C-clamp, a belt....
    What was the DTV (Disc Thickness Variation) after grinding with this setup? If anything more than about .0003" I would say that the setup is not rigid enough.

  16. #11
    Join Date
    Oct 2006
    Location
    Vancouver, B.C.
    Posts
    1,026
    Post Thanks / Like
    Likes (Given)
    84
    Likes (Received)
    174

    Default

    I would expect that for a 99 Dodge 2500 Digger Doug's set up worked extremely well for someone with the necessary skills and knowledge (which he obviously has). For the record, when working on his Ferrari he uses a 1/2 HP motor and a bigger C clamp.

    Dave

  17. #12
    Join Date
    Nov 2002
    Location
    St.Louis, Missouri, USA
    Posts
    1,928
    Post Thanks / Like
    Likes (Given)
    115
    Likes (Received)
    424

    Default

    I don't know what you have with out seeing a picture but may be ceramic coated or something and the auto parts shop doesn't have the right equipment? If they're cast iron and are heavy enough in cross section (vented with cooling ribs) I don't see the problem. I would want to set it up to be able to face both sides in one set up, perfect parallelism is the only concern for proper performance. A little run out is tolerable in the assembly.

    True experience; I bought a new truck one time and it made a funny noise as soon as I drove it off the lot when braking but stopped smoothly? Took it back to the dealer and didn't find anything wrong, I jacked it up and spun the wheel and could visually see the caliper going in and out. Pulled the wheel and rotor and found it had a faulty hub, about .045" run out at the edge of the mounting flange (about .060" at the edge of the rotor)? Went back to the dealer and told them what I found and told them I wasn't driving it like that, they replaced the hub,installed the same brake parts and sent me out the door with it. Never had any trouble with the brakes again. The bushings in the caliper mount were getting a work out but it stopped perfectly so really run out isn't a factor in brake performance but might affect how long the brake parts last.
    Dan

  18. #13
    Join Date
    Mar 2012
    Location
    Geilenkirchen, Germany
    Posts
    1,972
    Post Thanks / Like
    Likes (Given)
    1180
    Likes (Received)
    976

    Default

    I have noticed that with many new rotors they don't stay straight. Just after a couple of months use , they are warping. This issue is appearing across all brands, domestic and imported. This does not appear to be an issue (in my experience) with OEM parts. It has been impossible to tell where these rotors are being made, but I suspect China. I suspect the issue is excessive internal stresses left over from the casting process and with the heating and cooling from normal use the discs are stress warping. The argument of replacement being cheaper than turning is not so viable anymore. Has anyone else had this same experience?

  19. #14
    Join Date
    Jan 2007
    Location
    Pinckney Mi.
    Posts
    3,011
    Post Thanks / Like
    Likes (Given)
    4577
    Likes (Received)
    792

    Default

    I have seen rotors milled flat on a cnc mill, simple circle.
    Gw

  20. #15
    Join Date
    Oct 2005
    Country
    UNITED STATES
    State/Province
    Pennsylvania
    Posts
    10,598
    Post Thanks / Like
    Likes (Given)
    17619
    Likes (Received)
    5571

    Default

    Quote Originally Posted by LexD View Post
    What was the DTV (Disc Thickness Variation) after grinding with this setup? If anything more than about .0003" I would say that the setup is not rigid enough.
    It's a "WORK TRUCK"....and they were so bad before, it shook.

    Do you really think the brake lathes do "three tenths" ?

    Note it's a GRINDER set up, the forces are much lower.

    GET REAL.

  21. Likes sudsy55 liked this post
  22. #16
    Join Date
    Feb 2010
    Location
    Sweden Linkoping
    Posts
    164
    Post Thanks / Like
    Likes (Given)
    10
    Likes (Received)
    67

    Default

    I have turned discs to very good function. I have turned a pre-drilled/threaded blank to a "hub". (Every time I have to set up a disc I just have to first thru up the face of the hub with a light cut.) When you turn the disc you have to select a very low rpm and a low feed. Both sides of the disc has to be cut "in the same cut" (simultaneously). You need carbid bits for cast iron.
    I have a photo of the tool bit holder. The holder is "home made". When I adjust the bits for a new cut, I can move one by the compound slide and the other one by to loosen the clamp and tap it in a little.
    We had a situation here with new Ford brakes. After just a 1000 km the pedal started to vibrate and puls. Ford changed the discs, the same was happen again and again. I turned a used pair of discs from this car, in the way I have described here. The discs was without remarks after that.
    New discs has some tension in it. When you start to use it, it is heated up and cooled down. The tensions will be more and more tired but the discs will start to wobble.
    To turn a way that "wobble" on a used disc my way, makes it better than a new one.img_0797.jpg
    Good Luck and a Happy New Year

  23. Likes dfw5914 liked this post
  24. #17
    Join Date
    Jan 2007
    Country
    UNITED STATES
    State/Province
    Florida
    Posts
    974
    Post Thanks / Like
    Likes (Given)
    110
    Likes (Received)
    365

    Default

    here is a slide show made by a brake pad manufacturer that has some VERY good information about turning rotors
    http://www.oeqf.com/techinfo/scratch...atching_lg.htm
    under tips and techniques i believe there is one small error where they say rotor thickness should not exceed .0003 which i believe should say .003
    (looking in a workhorse service manual it says exceeding .002)

  25. #18
    Join Date
    Jul 2009
    Location
    NW Illlinois USA
    Posts
    326
    Post Thanks / Like
    Likes (Given)
    37
    Likes (Received)
    91

    Default

    I set up an extra steering knuckle vertically on my milling machine and spun the rotor on its own bearings with a vee belt. Then used the mill as a lathe with a single point cutter. Worked great. If you don't have an extra knuckle you could make a stub to serve to hold the bearings.

    This was for unobtainable or prohibitively expensive vintage parts that I would not trust anyone else with.

  26. #19
    Join Date
    Sep 2002
    Location
    Riddells Creek,Victoria,Australia
    Posts
    451
    Post Thanks / Like
    Likes (Given)
    60
    Likes (Received)
    49

    Default

    Quote Originally Posted by digger doug View Post
    It's a "WORK TRUCK"....and they were so bad before, it shook.

    Do you really think the brake lathes do "three tenths" ?

    Note it's a GRINDER set up, the forces are much lower.

    GET REAL.
    OK, your reply tells me that you did not check anything after machining, you just assume that they they are better than they were which is fine as long as you are happy with the result.

    Three tenths disc thickness variation can easily be achieved on a brake lathe or any lathe or grinder suitable for the job as long as it is set up and operated correctly.

    Note: I am referring to DTV not runout (TIR), which is completely different.

  27. #20
    Join Date
    Feb 2005
    Location
    Upstate, N.Y. USA
    Posts
    535
    Post Thanks / Like
    Likes (Given)
    12
    Likes (Received)
    3

    Default

    There is a nice video on YouTube where the guy cuts rotors on his milling machine with a rotary table and a fly cutter. Easy setup and nice finish! I don't remember his name,should be a easy search? I will do it for my used rotors when I have a chance.

  28. Likes Chip Chester liked this post

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •