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Drilling out a bottom bracket after a frame has been constructed ??

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Drilling out a bottom bracket after a frame has been constructed ??

Old 05-03-13, 11:50 AM
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systemBuilder
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Drilling out a bottom bracket after a frame has been constructed ??

I have a junker frame (1980 Carlton-made 531 db main tubes, Suntour GS dropouts, split seat lug) with a really thick sand-casted bottom bracket. I understood from asking a question on the bikelist version of this forum, about 4 years ago, that I could use a very long 400mm seatpost to solve the lug-splitting problem (tube has split for about 1cm below the seatlug, straight down, as if some idiot used a hacksaw to open the seat lug for a higher-diameter seatpost.)

Many vintage 1960's and 1970's have something like a 2.5mm BB shell, but this one has one that's at least 50% thicker, and is very plain in appearance, and is probably a significant percentage of the frame weight (Carlton XYZ in http://www.ece.ubc.ca/~gillies/raleigh/weights.txt). Bike has Bocama Pro (teardrop cutout) lugs.

I would like to drill some holes in the bottom bracket. One possibility is to drill "CC" in it, which was used for some top-end Carlton Pro's a few years earlier. Another possibility is to just drill large holes, like an old Cinelli, to lighten it up. It would be nice to reduce the weight by 30-50 grams. If I cannot reduce it that much, I probably won't bother.

Has anybody done this after construction? Too much of a pain to be worthwhile? Too difficult to do? The CC cutout has square letters, so it probably involves just drilling 4 large holes per letter and then cutting & filing between the holes to get the proper effect. I might use this for practice, and do it for real with another frameset I have (1968 competition), which is unbelievably heavy in the frameset, about 150 grams heavier than a typical 24.5" frame, but has a very light 700 gram fork (see url above, 1968 competition is a 2370 gram frameset, 180 grams heavier.)

- Don Gillies
San Diego, CA, USA

P.S. I don't read this forum too often, please cc me (gillies@ece.ubc.ca) on any responses. I will put a reminder in my calendar to check this group again, periodically.

Last edited by systemBuilder; 05-03-13 at 11:53 AM.
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Old 05-03-13, 05:58 PM
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Don- Of course some cut outing can be done after construction. But things will be a bit more difficult. Access and finishing without paint damage are the two biggies. Do you have a jeweler's saw? Andy.
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Old 05-04-13, 02:06 PM
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Sounds like a lot of work for no benefit.
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Old 05-04-13, 08:36 PM
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Decades ago, a bike painter locally used to do this for clients as a way to personalize their bike. It is work, a jewelers saw will probably not be the answer as those are generally coping saws and there is no room for the saw frame really.
I would go the "Cinelli" or as seen on early Colnago Supers, a 12-13 mm did hole surrounded by slightly smaller, like 9 mm piercings.
There are some other things you could do depending on what is in the way such as cable guides and such
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Old 05-06-13, 04:42 AM
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Originally Posted by systemBuilder View Post

P.S. I don't read this forum too often, please cc me (gillies@ece.ubc.ca) on any responses. I will put a reminder in my calendar to check this group again, periodically.
Can't you subscribe or something so you get an email alert when there are replies ?
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Old 05-06-13, 02:31 PM
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I would agree with others; time would be better spent riding it rather that screwing around with it, but if you do decide to add some drillium to the BB, be sure to put in one of those plastic BB accordian tubes in to protect your balls from the elements. Also recommend hitting the insides of the frame with FrameSaver as you will effectively opened it all up to the elements.

/K
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Old 05-07-13, 02:44 PM
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Originally Posted by ksisler View Post
I would agree with others; time would be better spent riding it rather that screwing around with it, but if you do decide to add some drillium to the BB, be sure to put in one of those plastic BB accordian tubes in to protect your balls from the elements. Also recommend hitting the insides of the frame with FrameSaver as you will effectively opened it all up to the elements.

/K
I wouldn't worry too much about the corrosion. It's nature's way of drilling lightening holes, there should be some lube in there, and the holes will probably help drain water.

When I was a kid we used to drill holes in the Chouinard climbing nuts we had. Lots of them. We didn't have people on the internet to ask about it. By the time you get to the point where you are making custom bikes you normally don't have a lot of interest in these lipstick on a pig exercises, but we all start somewhere.
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Old 05-08-13, 07:22 AM
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[Quote: Originally Posted by ksisler I would agree with others; time would be better spent riding it rather that screwing around with it, but if you do decide to add some drillium to the BB, be sure to put in one of those plastic BB accordian tubes in to protect your balls from the elements. Also recommend hitting the insides of the frame with FrameSaver as you will effectively opened it all up to the elements.
/K. Unquote]

[Quote - MassiveD said; I wouldn't worry too much about the corrosion. It's nature's way of drilling lightening holes, there should be some lube in there, and the holes will probably help drain water. Unquote]

Massive one; I understand that the spindle and bearings have (or should have) some looobe on them and that is good. But by drilling holes in the BB, that area is now open to splashed water, humidity, sand, dirt and whatever including a garden snake I once found living in a seriously lightened Columbus frame. And with the BB open, then so are the DT, ST, HT and TT as all of them are effectively linked together by the holes drilled into them to facility brazing or welding.

So I will stick with my initial recommmendation to give it a good dose of FrameSaver which pretty much dictates he tear it down to the bare frame to do so. Admittedly the frame in question is not of the highest quality, but I have found that when we care for every frame/fork as if it were a nice C&V item, then our standards of practice are always adequate...

Thoughts?

/K
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