Results 1 to 15 of 15
  1. #1
    a real member's member
    Reputation: blackfrancois's Avatar
    Join Date
    Jul 2016
    Posts
    3,678

    cutting new threads on a caliper bolt

    i want to use this 1985 campy triomphe brake on the rear in a recessed frame for my '87 falcon.



    i can use it nutted just fine. but i want to use a recessed nut. two questions:

    1. can i cut new threads in the unthreaded portion of the bolt?
    2. what is the pitch? in other words, what die do i use?


    backstory:
    i scored an '85 univega with a near full campy triomphe group to use as a donor for a couple project bikes, both from '87. one is an '87 falcon. the two triomphe brakes are identical. (and the whole group is pristine.) the two brakes look like two front recessed brakes. like many univegas from the era, the front brake was recessed, and the rear was nutted. i want both brake bolts recessed in my falcon. i will shorten the rear bolt with a hacksaw as well.

    thanks.
    Yossarian: don't worry. nothing's going to happen to you that won't happen to the rest of us.

  2. #2
    RoadBikeReview Member
    Reputation: velodog's Avatar
    Join Date
    Sep 2007
    Posts
    7,189
    There's a good chance that those are hardened bolts that the cutting tools won't impact.
    Too old to ride plastic

  3. #3
    RoadBikeReview Member
    Reputation: velodog's Avatar
    Join Date
    Sep 2007
    Posts
    7,189
    You may have to sell your 1st born, but this should work.

    https://www.ebay.com/itm/CAMPAGNOLO-....c100010.m2109
    Too old to ride plastic

  4. #4
    RoadBikeReview Member
    Reputation:
    Join Date
    Sep 2009
    Posts
    552
    Yes you can cut the threads higher on the bolt. I don't think it's harder then a grade 5 bolt and I have no problem cutting them with a HSS thread die.

    I don't know what size thread it is but you can measure it and find out. Measure the diameter of the bolt (above the threads) and the pitch (distance between threads). M8x1.0 or M8x1.25 would be my guess but it could be something else.

  5. #5
    RoadBikeReview Member
    Reputation:
    Join Date
    Oct 2013
    Posts
    2,760
    It would be easier to get the ebay part.
    You can take the nut to the hardware store to determine pitch, etc.
    If you never cut threads before, and you don't know how hard that bolt metal is, it would be way easier to go the ebay way.
    BANNED

  6. #6
    a real member's member
    Reputation: blackfrancois's Avatar
    Join Date
    Jul 2016
    Posts
    3,678
    thanks for the replies.

    i looked on ebay, and i'm glad i did. i found a package deal for $36 shipped that included ...

    - two victory recessed brake calipers
    - two record non-aero levers
    - the italian threaded top portions of a victory headset.

    the victory and triomphe brake calipers are the same except for the locknut, so that rear victory's recessed bolt should work just fine. and i think those nr brake levers are worth $30-$40, so this was a no brainer.
    Yossarian: don't worry. nothing's going to happen to you that won't happen to the rest of us.

  7. #7
    'brifter' is a lame word.
    Reputation: cxwrench's Avatar
    Join Date
    Nov 2004
    Posts
    13,443
    Dies are not for cutting threads, they're for cleaning up damaged threads (known as 'chasing' threads).
    I work for some bike racers
    I've got some bikes, some guns,
    and a bunch of skateboards

  8. #8
    tlg
    tlg is online now
    RoadBikeReview Member
    Reputation: tlg's Avatar
    Join Date
    May 2011
    Posts
    13,094
    Quote Originally Posted by cxwrench View Post
    Dies are not for cutting threads, they're for cleaning up damaged threads (known as 'chasing' threads).
    Thread cutting dies are absolutely used for cutting threads, hence the name. If you're cleaning up threads, you'd use a rethreading die.



    In the OP's case, it'd be damn near impossible to cut threads in that bolt. It requires quite a bit of torque to hand cut threads and there'd be no good way of holding the bolt.
    Custom Di2 & Garmin/GoPro mounts 2013 SuperSix EVO Hi-MOD Team * 2004 Klein Aura V

  9. #9
    RoadBikeReview Member
    Reputation:
    Join Date
    Oct 2013
    Posts
    2,760
    Quote Originally Posted by tlg View Post
    Thread cutting dies are absolutely used for cutting threads, hence the name. If you're cleaning up threads, you'd use a rethreading die.
    I agree, but I think you could take that bolt out of the caliper arms and put it in a vice.
    BANNED

  10. #10
    tlg
    tlg is online now
    RoadBikeReview Member
    Reputation: tlg's Avatar
    Join Date
    May 2011
    Posts
    13,094
    Quote Originally Posted by duriel View Post
    I agree, but I think you could take that bolt out of the caliper arms and put it in a vice.
    Well absolutely you have to take the bolt out of the caliper. But there's no good spot to secure the bolt in a vice. The hex portion is too small to clamp on without it pivoting or damaging the hex. You'd have to clamp on the shaft. But you wouldn't want to mar it because it's the pivot point. Perhaps a soft jaw vice would work. But as I said, it takes quite a bit of torque to cut threads. It'd probably spin in a soft jaw vice.
    Custom Di2 & Garmin/GoPro mounts 2013 SuperSix EVO Hi-MOD Team * 2004 Klein Aura V

  11. #11
    RoadBikeReview Member
    Reputation:
    Join Date
    Sep 2007
    Posts
    545
    As mentioned, thread cutting taps & dies are meant to cut threads and thread chasers are not so coincidentally meant to chase (clean-up) existing threads. Chasers are not meant to cut threads, and thread cutters will remove more material if used as chasers - not good.

    There is no way that brake bolt is going to be hardened, as hardening adds brittleness. Having a brake bolt snap during use would not be a good thing.

    You would need to remove the bolt from the caliper and clamp it in a vice to extend the threads. Depending on the style of vice you have, you may need to thread/lock a few sacrificial nuts on the other threaded end and clamp those in the vice - so as not to damaged the other threads.

    However, there is a bigger problem. If you look closely, you will notice the OD of the threaded portion is visibly smaller than the OD of the shaft of the bolt. Thread cutting taps and dies assume you have the correct inside or outside thread diameter respectively before you start cutting the thread. Attempting to cut a thread on a bolt with too large a diameter will result in a broken bolt, or a broken tap if cutting in internal thread in an undersized hole. So, unless you have the means of turning down OD of the shaft of the bolt you wish to extend the threads into, it's going to be a non-starter.

    Extending threads on a rear brake bolt might not be too unsafe since the brake is being driven into the frame, but there is no way I'd want to mess with a front bolt. Unless you knew exactly what you are doing to avoid weakening the bolt or adding stress risers, I would not suggest modifying such a bolt. Life could become rather interesting if the bolt snaps while braking.

    So, long story short, that $40 bolt is definitely the way to go.
    Last edited by RHankey; 3 Weeks Ago at 06:58 AM.

  12. #12
    RoadBikeReview Member
    Reputation:
    Join Date
    Oct 2013
    Posts
    2,760
    If the bolt shaft change OD, one would just cut that end that is threaded now off. Then you could just use a bigger die with a bigger nut.
    But that would negate using the double nut vice attachment.
    I'd just put it in the vise and polish up the surface once done.
    BANNED

  13. #13
    tlg
    tlg is online now
    RoadBikeReview Member
    Reputation: tlg's Avatar
    Join Date
    May 2011
    Posts
    13,094
    Quote Originally Posted by duriel View Post
    If the bolt shaft change OD, one would just cut that end that is threaded now off. Then you could just use a bigger die with a bigger nut.
    But that would negate using the double nut vice attachment.
    That wouldn't work. If it's larger, it's larger by a fraction of a mm. It wouldn't be an entire mm larger, which the next size nut would be. Plus he wanted to use a recessed nut. Doubtful the next size larger recessed nut would fit in the frame (if they're even made).


    I'd just put it in the vise and polish up the surface once done.
    Pretty sure that's a plated bolt. So now you've got a potential rust location inside your pivot.
    Custom Di2 & Garmin/GoPro mounts 2013 SuperSix EVO Hi-MOD Team * 2004 Klein Aura V

  14. #14
    RoadBikeReview Member
    Reputation:
    Join Date
    Sep 2007
    Posts
    545
    Quote Originally Posted by duriel View Post
    If the bolt shaft change OD, one would just cut that end that is threaded now off. Then you could just use a bigger die with a bigger nut.
    But that would negate using the double nut vice attachment.
    I'd just put it in the vise and polish up the surface once done.
    That would be a bodge at best. The OP says he needs to extend the threads so he can mount the brake to a recessed frame mount. Going to a larger diameter thread would result in less (insufficient) material on the corresponding recessed nut unless one starts modifying the brake boss hole too. And of course, that all assumes the OD of the unthreaded shaft corresponds to any standard nut/bolt standard, and secondly that one could find a recessed nut with the slightly larger diameter thread (while maintaining all the other geometry to fit in the unmodified frame. I personally could easily machine any diameter thread/pitch with corresponding nut, but then the next poor sod who wants to work on the brake is going to be in a lurch.

  15. #15
    a real member's member
    Reputation: blackfrancois's Avatar
    Join Date
    Jul 2016
    Posts
    3,678
    Quote Originally Posted by RHankey View Post
    you may need to thread/lock a few sacrificial nuts on the other threaded end and clamp those in the vice - so as not to damaged the other threads.
    had i not already taken the advice to buy a donor bolt from another brake, i think this is good advice.

    However, there is a bigger problem... you will notice the OD of the threaded portion is visibly smaller than the OD of the shaft of the bolt... it's going to be a non-starter.
    i thought about that, and i thought i could file it down before i started with the die.

    So, long story short, that $40 bolt is definitely the way to go.
    you all convinced me... but i'm still curious to see if cutting the threads would work. i may revisit this later.
    Yossarian: don't worry. nothing's going to happen to you that won't happen to the rest of us.

Similar Threads

  1. Replies: 9
    Last Post: 08-21-2014, 01:01 PM
  2. Bolt for Brake Caliper too short.. what to do?
    By mwilcko2 in forum Components, Wrenching
    Replies: 6
    Last Post: 09-01-2007, 01:49 AM
  3. Cutting new threads in a threaded fork?
    By foggypeake in forum Components, Wrenching
    Replies: 18
    Last Post: 07-05-2007, 09:01 PM
  4. bolt cutting
    By Travis in forum Fixed/Single Speed
    Replies: 5
    Last Post: 01-13-2007, 01:30 PM
  5. serrated washer on brake caliper bolt?
    By eflayer2 in forum Components, Wrenching
    Replies: 2
    Last Post: 05-02-2006, 06:38 AM

Posting Permissions

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

THE SITE

ABOUT ROADBIKEREVIEW

VISIT US AT

© Copyright 2018 VerticalScope Inc. All rights reserved.