Bicycle Mechanics - Bottom brackett threads
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How can I clean out the bottom brackett threads with out paying a bike shop to use their expensive taps?
the sand blaster ruined some of my threads...I would try a nail but I can't even see wherer to use it.
09-11-12, 01:19 PM
You can make a thread chaser out of an old BB cup. Using a grinding tool, e.g. Dremel or functional equivalent, cut some slots into the threads on the cup:
Use your regular BB tools to run the chaser through the threads to clean them out.
09-11-12, 01:20 PM
09-11-12, 02:46 PM
I tried a similar tactic without the slots through the threads (great idea BTW) on an Italian bottom bracket where a thin Campy BB had been used in the frame for a long time and I replaced it with a thick BB and threads in the shell were pretty gunked up past the reach of the thin BB. I tried a wire brush, Dremel tool and solvents with no success. Unfortunately there was no BB cup I could use accept another thick Italian and I didn't have one to waste. I screwed the thick BB in and it pretty much stopped dead in it's tracks where the end of the thin BB would have stopped. I tried using a little more force to see if I could chase the threads, but I wasn't willing the sacrifice either the shell or BB. Fortunately a friend that owns an LBS (with he closed last month :cry:) had an Italian BB die and for $20 he chased the threads (because it's Italian the tap went from the right side all the way through and came out the left side). My best to the OP, I hope he had more luck then I did..
09-11-12, 03:14 PM
just that the thread chasing using an old cup, will only be so far in ,
on the right, sticking to a similar BB its probably OK ...
cutting oil is a machinist's best friend in these situations..
09-11-12, 04:19 PM
Since the lead-in threads are distorted or missing you may have difficulty getting a makeshift tap to start and run straight; gettting it started crooked or jamming it could cause more damage. Depending on the value of the frame involved, paying for the use of a proper tap could be a wise investment.
09-12-12, 12:21 AM
Since the lead-in threads are distorted or missing you may have difficulty getting a makeshift tap to start and run straight; gettting it started crooked or jamming it could cause more damage. Depending on the value of the frame involved, paying for the use of a proper tap could be a wise investment.Good point! If the threads are more or less flattened out, you need to make sure that your makeshift chasing tool is on straight. The best way to do this is to thread it on by hand as far as possible. It's also highly unlikely you will be removing any metal, so there should be very little resistance. Best to use a short tool (ie 8") so you won't have enough torque to do any real damage.
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