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  1. #1
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    cutting my headtube

    I have a new colnago mix that I got for really cheap on eBay. I like the geometery a lot except I would like the head tube to be a bit shorter-- it sticks up about 1.5cm above the top of the top tube. What is the best way to cut this off. I brought it to my LBS and asked if they would just use the facing tool to cut it down to the point I wanted (about 1cm) and they wouldn't do it. They said the Al frame is too soft and could deform causing problems with my headset fitting and overall longevity of the frame. Any suggestions?

    Thanks

  2. #2
    Recovering Retro-grouch CRUM's Avatar
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    Add in the fact that removing 1 cm of aluminum is likely to ruin their facing cutter, they were smart to refuse. Aluminum is particularily hard on cutting tools.

    But the big point here is not the tool but messing with the original frame design and construction. I would assume the frame builder had a very good reason to make the headtube the length it is. Strength vs. Tube material and thickness come to mind as one possiblity. If you want a lower position, install a negative rise stem.
    Keep it 'tween the ditches

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  3. #3
    Senior Member (Retired) gmason's Avatar
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    Damn, cut it twice and it's still too short.

  4. #4
    Recovering Retro-grouch CRUM's Avatar
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    Quote Originally Posted by gmason
    Damn, cut it twice and it's still too short.
    Are you really a French Canadian from Maine?
    Keep it 'tween the ditches

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  5. #5
    Senior Member sydney's Avatar
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    Quote Originally Posted by CRUM
    Aluminum is particularily hard on cutting tools.
    Where did you dredge that up from?

  6. #6
    Recovering Retro-grouch CRUM's Avatar
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    Quote Originally Posted by sydney
    Where did you dredge that up from?
    From my own experience using the exact tools mentioned.
    Keep it 'tween the ditches

    My Blog - Lost in the Bo Zone

  7. #7
    Senior Member sydney's Avatar
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    Quote Originally Posted by CRUM
    From my own experience using the exact tools mentioned.
    If you say so,but even at that it seems using a facing tool to to try and remove 1cm is the Bubba way.

  8. #8
    Senior Member mtbikerinpa's Avatar
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    Removing that dramatic an ammount of head tube does not seem like a wise option regardless of the tools. The frame designer had it that way for a reason, whatever that was. I agree with the previous poster that suggested a negative stem if lower bar position is the desired effect.
    If the desired effect is not ergonomic and is in fact cosmetics, then it is different. One aspect to consider is making your press-fit zone for the headset too close to your head tube/top tube weld. It is not neccesarily endemic to have it there, but it is not ideal. A serious modification such as that is a one-way deal. If it later causes a problem or is dissatisfactory, you cannot add it back on or repair it. I agree with the shop on the matter of possible deformation of the fit of your cups.

    On the matter of AL being harder on the facer than steel. Hardened 7000 series will be near steel in hardness. 6000 series will be more malleable but can still be hardened up sizably. The difference though is aluminum will shave differently and in larger particulates. It will also fill grinder stones in certain situations.
    Aviation Mechanic, Bike racer, Fitness Equipment Restorer

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  9. #9
    Recovering Retro-grouch CRUM's Avatar
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    Quote Originally Posted by mtbikerinpa
    On the matter of AL being harder on the facer than steel. Hardened 7000 series will be near steel in hardness. 6000 series will be more malleable but can still be hardened up sizably. The difference though is aluminum will shave differently and in larger particulates. It will also fill grinder stones in certain situations.
    Back in the 80's when most of the frames we built up from Europe were of steel, chasing and facing was absolutely necessary. A cutter would last me it seemed forever. The turnings on the steel tubes coming out in agreeable and uniform spirals. Along came Aluminum frames and all of a sudden, we were chipping edges of the cutters and either having to ship them back for re-sharpening more often or having to buy new ones. Alloy may indeed approach the hardness of steel, but I think the tools were harder to control on aluminum and would bite in more than intended, creating divets in the edge that then needed more facing to remove. I do not know why aluminum was tougher on my tools but it surely was. All I know is I approach alloy frames with way more caution than I do steel. And of all the frame materials I hated using any facing, reaming or chasing tool on, Boralyn frames from Univega were the worse. Some ungodly hybrid alloy mongrel material that laughed at any attempt to work it's edges , threads, etc.
    Keep it 'tween the ditches

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  10. #10
    Senior Member Nessism's Avatar
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    The Mix frame has a constant diameter head tube so if you trim off a few mm's without concern for what it'll do to the frame, just stay out of the welds.

    Carefully measure down from the existing edge of the head tube and mark a cut line all the way around. Now take a hack saw and cut. Work your way around slowly keeping above your line. After you seperate off the extension, take a bastard cut file and smooth out your cut. Lastly, take the frame to a shop that can face it.

    I cut the bottom of the head tube on my TST titanium frame because the frame was designed for a shorter length fork than the one I wanted to use. It was fairly simple to cut if off but the facing took a while.

    All this said, I'd leave the frame alone. The Mix head tube is not "too" high, just run a -17 degree stem and no spacers.

    Good luck.

    Ed

  11. #11
    Senior Member (Retired) gmason's Avatar
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    Quote Originally Posted by CRUM
    Are you really a French Canadian from Maine?
    Nope. I am a 'murcan from Brooklyn (originally - don't hold me to that since the Dodgers left).

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