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Thread: Inside your lugged BB's..

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    Default Inside your lugged BB's..

    Wondering how you guys are dealing with the inside finishing of your lugged bb's? Namely do you leave the tubes sticking in a little, then die grind then tap? I came across this pic and it looked to me like that is what was happening there.

    On the lugged bb's i've done i've done a decent mitre but it looks no where as flush and clean on the inside when done. I know this ventures in to one's own process and tooling setup but what are you thoughts on how this was done?

    Cheers

    Tim

    EDIT this is a picture from Dave YBarolla's flickr.I commented on the pic so hopefully I can get his insight too!
     

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    Default Re: Inside your lugged BB's..

    a bit of tube inside
    and die grinder and tap
    looks sweet
    it's like what is beneath the lingerie :-)
    Cheers Dazza
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    Default Re: Inside your lugged BB's..

    I do what Dazza says plus use a wire brush attached to a pneumatic drill to remove any oxidation from soaking and give it sime shine.

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    Default Re: Inside your lugged BB's..

    better flush or a hair through than cut back atmo.
    the tap will always show it who's boss.

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    Default Re: Inside your lugged BB's..

    Jeff leaves about half a mm of ledge. Ie. he miters to the shell but then pulls back about 0.5mm. Not quite flush. He makes sure that the down tube overlaps the seat tube by about half a mm as well so that it is not just the shell holding the frame together. He does not leave the extra down tube in the middle, but miters that off. Helps?
    Tom Kellogg
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    Default Re: Inside your lugged BB's..

    Well, after that roll call, there's nothing I can contribute other than it sure as sh*t shouldn't look like this.
     

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    Default Re: Inside your lugged BB's..

    Quote Originally Posted by pruckelshaus View Post
    Well, after that roll call, there's nothing I can contribute other than it sure as sh*t shouldn't look like this.
    pete - the riv frames stay together atmo, and are sold at price points.
    i'd say they're more reliable on almost any level than a frame from the
    average flickr god or blog queen posting these days after his 16th try.

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    Default Re: Inside your lugged BB's..

    I would advise anyone trying to market a production frame not to do the cutaway thing. In my teen years I saw a high-end frame that had been cut away and the top tube was clocked with at least a 1/8" gap. The truth is that if it had been sold instead of hacked apart at a machine shop, the owner would have been perfectly happy with it. And if you look at the old collectible bikes from prestige builders that people swoon over, most of them have brutally un-photogenic joinery inside the bb shell. Photogenic bb interiors are a bit of an affectation, but in the end it make sense.
     

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    Default Re: Inside your lugged BB's..

    Quote Originally Posted by pruckelshaus View Post
    Well, after that roll call, there's nothing I can contribute other than it sure as sh*t shouldn't look like this.


    At least there's enough coverage with the brass to keep her solid.... not pretty but solid. I wonder if I could fill that size gap with my TIG.... Hmmmm....

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    Default Re: Inside your lugged BB's..

    Here's how I do mine.





    Last edited by zank; 02-04-2011 at 01:04 PM.
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    Default Re: Inside your lugged BB's..

    Zank - that is awesome... here's Daves reply and thanks all thought I'd post to close the loop.

    ybarrola_bicycles (17 hours ago | reply)
    Yes, I let them both stick through a small bit. Maybe 1 mm. When I am brazing it is easier to see the silver coming through from the outside in and see it once it hits those little 1 mm extensions. Don't leave too much or you will be grinding forever.
    Then I grind it off and tap the BB. What you are going for is 100% penetration. Total filler everywhere.
    It's amazing the number of bikes (production) that are not made this way. I've seen a lot that are just cut at 90 deg, leaving lots of area uncovered.
     

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    Default Re: Inside your lugged BB's..

    Zank, correct me if I am wrong but from that first pic it looks like your seat tube is supported by a little extra down tube sticking through, is that correct?
     

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    Default Re: Inside your lugged BB's..

    You bet. Very similar to Tom and Jeff's process.
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    Default Re: Inside your lugged BB's..

    Zank, that cutaway bike is awesome.

    Nothing worse than having a seat tube sink into the bb and not notice it. The way the early treks were mitered that could happen, and then the bike would be hard to get off of the jig. Not fun when you have a quota to meet.
     

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    Default Re: Inside your lugged BB's..

    Quote Originally Posted by Dornbox View Post
    I wonder if I could fill that size gap with my TIG.... Hmmmm....
    That's the beauty of TIG. Gap? What gap?
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