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Cross threading. Darn it.

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Cross threading. Darn it.

Old 01-21-19, 12:26 PM
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MiloFrance
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Cross threading. Darn it.

Hi all. I bought an after market French threaded BB for a steel frame. It arrived, I lined it up and gently started to ease it in (fixed side). It almost immediately went sideways with very little pressure. Taking it out I was a bit surprised that the alloy was so soft that it had been damaged by so little at the start of the thread. Using a needle file I took the damaged bit off and tried again. No matter what I do, it won't go. It is the correct thread, I've done many of them before and all the threads are clean
Any other suggestions please?
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Old 01-21-19, 12:42 PM
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Bill Kapaun
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Are you turning it backwards until you feel a thread "drop in" before screwing it in?
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Old 01-21-19, 12:58 PM
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You're sure it is French, right? And, you have the right/left threading correct. Swiss?

You might hunt down some steel cups that you could try first, before you tear up your aluminum cups any more.
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Old 01-21-19, 01:36 PM
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...sometimes it helps if you put in the non fixed cup first, and screw it in just a few turns (not all the way). This gives you a smaller hole for the spindle to exit on that side, which in turn helps to straighten and center the sealed unit with the fixed cup that is integral to it. Then youi do the backward turning until you feel a little click business, and you should be OK. Anyway, that's how I do them.
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Old 01-21-19, 01:45 PM
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Have found over the years that some manufacturers just cannot hold tolerances very well. Had some bottom brackets that just has threads a tad oversize. Very frustrating but it happens.
Example:
Carefully chased frame with proper taps. Nice n clean and lubed.
Had several brand new BB's in the shop.
Some were quite a loose fit and even rattled a bit until torqued. Some were very good fit. Some were kind of snug by hand. One brand was super tight. One brand just would not go in.

Bottom line is that it seems thread quality can be all over the place.

Good luck.
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Old 01-24-19, 03:21 PM
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Do you happen to have an under the bottom bracket cable guide? If you haven't already done it, I'd check for a screw or something similar hitting the bottom bracket as you try to install it.
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Old 01-24-19, 03:54 PM
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Originally Posted by 3alarmer
...sometimes it helps if you put in the non fixed cup first, and screw it in just a few turns (not all the way). This gives you a smaller hole for the spindle to exit on that side, which in turn helps to straighten and center the sealed unit with the fixed cup that is integral to it. Then youi do the backward turning until you feel a little click business, and you should be OK. Anyway, that's how I do them.
This is exactly what I do for two-piece cartridge bearings, where you have a cartridge assembly and then a non drive side "cup" as a retainer.

But I join @CliffordK in asking if you know in absolute certainty that it's French-threaded. Swiss threads use the 35x1mm French threads, but the drive side is left hand thread (like English and others) rather than the French's right hand thread.
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