Guys I have some problems with my bottom bracket here.

I think I have cross threaded my bottom bracket shell,
the bottom bracket cannot get into the shell correctly, it always misaligned itself after a few turns,
if I forced it to align properly, it will not fit into it at all, the after one turn it will pop up itself,
after studying to the threads, I came up with this :



Red color - Cross threaded line
Yellow color - original line where it should be



Is it possible to rechase the threads?
or can I sand off the first 3 rows of threads and still remain usable?

*sorry for bad English, it's not my main language.

Photos don't show.

Specialty Bike Shop/ Frame Builder BB Threading tools will, clean up the Buggered threads . then you Pay them and say 'Thank You'.

First, are the cups you're trying the proper thread? Second, are you turning them in the right direction (adjustable cups turn clockwise to install; English and Swiss thread fixed cups turn counter-clockwise to install. Third, have you cleaned the threads in the shell with a stiff wire brush?

If you've done all that and it still won't thread straight, you may need to get the threads chased. Since the cups seems to misalign as you install them, this may be a job for your bike shop, with a set of piloted taps to make sure things stay in alignment.

I've reuploaded the photo, thanks for inform.

Yes, I'm pretty sure I'm turning them into the right direction and using the right cups, and also I've cleaned it too.

The situation of my threads is something like this:

||\\\\\|
||\\\\\|
||\\\\/|
||\\\\\|
||\\\\\|

The first line of thread had been cross threaded, I'm wondering could I sand off the first row of thread , becoming:

||\\\ |
||\\\ |
||\\\ |
||\\\ |
||\\\ |

And thus still remain usable?

The simple answer is yes, if you could successfully grind off the first row of threads, you could make that work, but it would be tricky. Try the shop first to see if they can chase the threads.

Most shops will have tools to chase the threads. Pay them to do that... Should not be a big deal or an expensive fix.

Looks like you might want them to face off the outside of the BB, too...

Get a set of jeweler's files and get to work. It's tedious but you can do it in your living room. All you have to do is straighten out the first few threads so the bb goes in straight.

+1
You can carefully follow the groove of the thread and file away the damage.

.
...it's pretty simple with a pilot pin set of BB taps to chase right past the few threads that you have damaged. Unless you live so far out in the wilds that nobody within a hundred miles has a set of them, that's your best and most expeditious fix. Trying to file off a few threads in order to get the cups threaded in straight, while possible, is a lot more problematic than you might suppose.

You're looking for something that looks like this (in the proper threading for your BB).



There are a number of companies that make them in both standard (English) and Italian. French and Raleigh are hard to find.

There is such a thing as an internal thread file which would cost a lot less than the tool pictured above. A shops charge to use the above tool on your bike should be less than either. Here's just one example of an internal thread file. You might find it cheaper somewhere else.
Internal & External Thread Repair File / Pitches 9, 10, 12, 16, 20, 27, 28, 32

It's cute that you link to a $50 tool which doesn't even have the correct thread pitch for the job...

If you're going to go this route, probably go with this tool instead, which has a 24tpi file, and is $14: Thread Repair File 177-1 / Pitches 11, 12, 13, 14, 16, 18, 20, 24

But really, how many times is one going to use such a tool? Add in shipping on the cheap tool and you're probably close to what it would cost to have a shop chase the threads clean and face the outer edge.

Last time I had a "Chase & Face" done on a bare frame it was $20 while I waited.

No need to be snide, I had a minute to post and just wanted the OP to see what the tool looked like. I believe I DID say it was just an example and that they might find it cheaper somewhere. People can do their own research and shopping.
Neil

It would not do any significant harm to simply/carefully(!!) grind down or adjust the buggered section of thread. A ham handed user of the chaser taps
could do a lot of damage if the tap starts wrong and begins to cut a new set of threads. The BB cups will have enough thread engagement left if you
remove the offending part of the thread. I did this recently on a DA freehub that I managed to bugger about 25% of the circumference on the first two
threads by cautious use of a ball end dremel tool and salvaged the freehub, which has a lot less thread engagement on the cassette locknut than a BB.
A BB threader such as pictured rightly used would make short work of the buggered thread.

But it's so much fun!

Yes, and thanks for posting that link, which led to the cheaper tool in the correct pitch.

Sorry to state the obvious, but are you sure you are putting the cups on the correct side?

I've seen them attempted reversed and the results are as you describe...

Which is actually not always possible. Think about it like this, the shell was tapped with threads once to put the initial threading in. Crossthreading essentially buggered the threading but was essentially running a "bad tap" over the threads a second time. Running a tap a third time to clean everything up just might cause the metal of the raised threads to literally fatigue and give way. The caveat here is most LBS cyclists consider very good bike shops don't actually have the correct tools to retap a BB. In this case you'd want to see a Park BTS-1 or something similar from Campagnolo, VAR, or whomever (depending on English, Italian threading). The Park tool is a $450-600 tool. You'd be surprised how many bike shops with really good reputations don't have the correct tools to do even basic bicycle maintenance. Tools are very expensive, they walk away, and bike frames are more or less considered disposable at this point (carbon paradigm).

Usually there is enough threading to hold the bottom bracket bearings square in the BB shell, but sometimes there just isn't. You don't really know until you try to run a tap through, and even then until you try to install a BB in the cleaned up threads. It can look good but just "let go" when you try to install the BB.

If that happens its not the end of the world. Two tricks every mechanic should have in their toolbox to deal with buggered BB threading, or weird french threading, or even to just get away from Italian threading:

1. Mavic Bottom Brackets - Good bike shops (be advised these are few and fart between) would have the Mavic chamfering tools to install a compression fit Mavic SSC bottom bracket. Think sealed bearings. These are available in a variety of spindle widths if you search on eBay. Absolutely one of the all time best bottom brackets. Think Phil Wood equivalent. Yes they were that good. Strong enough for their 8-speed triple mountain bike group, good enough to win TdF Stages and GC wins (Sean Kelly and Lemond). Its a compression fit BB that permanently chamfers the BB shell. As such many cyclists elected to not use the Mavic BB because they didn't want to damage their vintage Colnagos, Olmos, Yetis or Pinarellos.

2. There are lower quality threadless Bottom Brackets out there. Velo Orange imports one they rebrand as Grand Cru from Taiwan or China. That's an option as well if all the local LBS near the OP are just hack shops without the correct tools to retap the BB or install a quality Mavic BB.

Back in the day, I installed a few of the Mavics. They really were top quality. I still have the chamfering mill in my tool kit. The Velo Orange unit doesn't need to have the BB chamfered.

+ BITD, such as the famed names steel Italian frames shipped them out expecting the retail shop to own the cutting tools,
to do the final thread cutting and reaming and facing.