My friend just had his Specialized Allez frame stripped and re-sprayed or dipped. I'm guessing the layers consist of primer, a few coats of candy apple red, a few coats of what I'd say was Burgundy red and then I guess a layer or two of clearcoat.

The problem is that some of the paint has ended up on the headtube faces and BB shell. I managed to get the paint off the headtube and face of the BB shell with a razor blade and a small file. However, when trying to thread the BB cups in, one side went in no problem, the other went in about three full turns and then got very hard to turn. It also seemed to be slightly askew.

Apart from using a re-tapping/re-threading tool, what can be used to dissolve/remove the paint in the BB threads (thinners etc) without any run off getting onto the other painted areas of the bike?

TIA

What you need is called a "tap", and you need to "chase" the threads. That's the way it's done.

You could try a wire brush to remove paint from the threads, but I suspect you'll likely need to pay a few bucks to your LBS to have them properly chase out the threads with bottom bracket taps.

It's pretty frustrating to scrape away paint in BB threads with a pick (often a 90* bend 1cm from point helps) but I've done some of this when a proper Bb chasing tap set wasn't at hand (and note the reference to a chasing tap set, as actually cutting new threads in a blank shell with the common taps can go really bad).


One other option that I also have done is to take a good quality BB cup and cut a trough (or two) across the threads to act as a cutting edge. basically making a chasing tool. This is harder then it sounds as the goal is to actually have a cutting edge which meets the thread tops at a sharp enough angle to cut and not mush the paint. The only one I did was with a Dremel and a cutting disk held at an angle to achieve the cutting edge angle. Then I reduced the thread height both before and after the cut. This tool worked well enough at the moment but was a lot of work. Winter in a underfunded LBS can make one take some time that would otherwise be wasteful during the season and when the proper tool was on hand. Andy.

Just take it to a shop and have them run a tap through it. Cleans out the paint and can guarantee that all the threads are good since the OP mentioned he may not have installed the BB straight. Shouldn't cost too much and cheaper than buying your own taps.

In rereading the OP I see we never really answered the question.


Various paint strippers do exist that might soften the paint/primer. A gel (as opposed to a liquid) version will tend to not run or spread on it's own. Applying only on the shell's ID and using the face of the shell as the "DMZ" while care is taken during the mechanical work to apply then scraping off will be the key to not effecting the outer surface of the shell. This method takes some time and reapplications. The results might still want a proper chasing or single point scraping to get down to bare metal.


Next time the frame gets painted there are methods to shield the threads. It's too bad the painter didn't use them this time. A small amount of prep can save a lot of clean up. The lack of doing so suggests the painter wasn't concerned of wasn't experienced. Perhaps a fuller pre painting discussion of expectations was in order. Andy.

It seems as though one may be better off simply loosening the original BB a few turns and leaving it in place during the painting process... especially if you're not intending to reuse it.

For sure. The guy is apparently an extremely experienced guy. I guess he didn't realise the importance of masking off the BB threads as bikes are not his usual subject. I must say that he did a great job of the painting process.

I'll see what my friend says when he gets back to me but, as others have said above, I feel that the shell will need cleaning out with the proper tool at the LBS.

Not that the bike cares but I do wonder the actual painting process. Was it powder coated, wet sprayed or dipped (which I doubt). If it was dipped then the insides of many other parts of the frame are likely coated too. Now if the dipped reference was to remove the old paint then my only follow up is the hope that the insides were completely drained and dried before primer/paint. Andy (who has used a number of painters, who were clueless about bike frames, once).

If the cup was cross threaded, your best option is to have the the threads cleaned up by a shop with the proper tool

Off hand I'd say the problem is more likely that you are cross threading the cup. That's nothing to do with the paint. Remove it and try again until it goes in straight. If you can't get it to thread straight then you'll need to get it chased and faced.

I had the same problem with the paint and went over it with a pick then wire brush. Worked fine - since it was Italian threaded might even help keep it tight.

OP says that the frame is a Specialized Allez, small chance that it is Italian threaded

Wire brush in a Dremel tool.

What he said.

No idea, Andy.

The BB cups went it and came out before the repainting job, hence why I believe it to be the paint that is stopping the threads of the cup aligning with threads in the shell. If it does turn out to be the threads after all, then my friend will have to get the threads chased/retapped at a local shop.

Paint in the threads is a good thing unless they impede the install of the cups. Then chasing or cleaning them should be done. I would be more concerned with the paint on the faces of the shell as when a cup comes in contact with that there it is almost a sure thing that the cup will lift the paint from the outside of the shell. The contact faces of both the head tube and bb shell should be lightly faced or filed carefully to remove all paint from those areas.
Paul

migrantwing, I've had my LBS face and chase most of my new frame set builds and I've found it money well spent. Even with a forgiving cartridge BB it is nice to have the NDS support collar thread up to the shell with finger pressure only.

Brad

My Soma Saga had paint in the bb threads and had to be chased, I bought it straight from them. I paid $25 for my LBS to install my bb and headset cups, they included chasing the bb threads.

Using a hand file on the shell? Screwing in the bottom bracket askew? Please, take the frame to a shop before you wreck it.

I wasn't screwing the BB into the shell askew, it was doing that of its own accord. Hence, why I stopped doing it and made the original post. As for filing the shell face, this is when it had primer, a few coats of paint, a few coats of another colour paint and also clearcoat on it. I didn't file down the metal of the shell face at all.

The facing of a BB shell is perceived to be an extremely important procedure. Whilst I agree with getting it to the 'best available' state, perfection is almost impossible, maybe entirely impossible. For both the shell faces to be perfect mirror images of themselves a perfect starting and reference point is required. I don't believe there is such a thing on a bicycle. How do you know that the internal BB shell threads are aligned correctly? Which side shell do you face first? When the chasing/facing tool is used, it needs that perfect reference point when using it. It cannot be done to perfection. To get it there, you would need alignment tools, measuring tools, and all other sorts of high end things to make sure that the BB shell, in relation to the frame was 100% perfectly aligned to many various other points of reference on the bike. It is impossible. Therefore, having a bottom bracket shell and faces that are not 100% perfect doesn't really matter as long as they are not ridiculously way off, obviously. Everything on a bicycle, like most other things unless high end machinery and tools worth hundreds of thousands, millions of pounds are made within so-so tolerances. Some better than others. I guarantee you your bike is not 100% aligned in every plane. I bet your chainrings are not 100% straight and running 100% parallel to the cranks. Then there's the slight play in the pedals, and then your ankles and feet. Are you sitting perfectly on your bike, all aligned correctly? Are your legs and arms of the exact same length? NOTHING is perfectly aligned. When I filed the paint off, I didn't file 10mm of BB shell aluminium with it, just the paint and then used a razor blade to scrape off the remaining primer.

Maybe one of these should be purchased by every cyclist RotorBike USA.com-Self Aligning Bottom Bracket

Anyway, my friend ended up taking the bike to the shop and getting the BB chased, maybe re-threaded and also had a new BB fitted at the LBS. The cost was of a decent price but a lot more expensive than the $25 Mr IGH paid. More like $100 over here in the UK.

Agreed.

It makes life a whole lot easier when those cups thread in by hand.

$25. That's a great price.

The frame shop I worked at faced the shell referenced to the threads, then aligned the frame on a surface plate with the shell bolted to the table using the face as the reference. It works.

If the frame is already built up and in the hands of a consumer then it might be an issue, esp if the frame wasn't built with the bb threads as the original reference for all subsequent alignment steps.

OTOH, the need for the faces to be perfectly parallel for a bottom bracket to work correctly has mostly past. If a cartridge bb is used then there's no need at all. In the case of Hollowtech II bb, there's some slop available in the nylon bushing that line the bearing and if the shell isn't too far off it'll work.

There are a few aspects of frame alignment that we could talk about.


The "tracking" alignment is when both wheels are placed in the same plane with each other (when going straight ahead). "Steering" alignment is when the frt tire contact patch, with the road, is in line with the steering axis and said axis is also coplanar with the ft wheel's plane. These two are usually grouped together for most discussions.


"Component" alignment usually refers to the BB shell, the head tube and fork steerer being coaxial, perpendicular and parallel WRT their axis and faces. This is what a set of frame finishing tools do (as in chase and face the shell, ream and mill the headtube and crown race). But also things like brake mounting holes being parallel to the wheels' planes, rear der mounts being perpendicular to the rear wheel (or whatever it takes to have the cage parallel to the cog set's plane), ft der braze on mounts properly located and even seat tube ID being round and straight cylindrically.


Then there's the "Bio" alignment. This is usually thought of as the BB shell being perpendicular to the frame's plane and centered WRT this plane. But the seat tube and head tube being planar to the frame's plane also is a part of the fit alignment. The seat and bars are centered and straight here too.


It doesn't take much imagination to see that these different alignment aspects overlap with each other to certain degrees. Also that some can be off with others spot on and that some people will claim the frame is straight or it's not so. I've made a frame where the tracking and steering alignment was very good yet the shell was twisted so badly that my knees felt it.


It's the goal of a builder to work all these alignments to a state where they fall within the human's ability to assemble the bike with the speced components in a good adjustment/function condition, to have the rider's body fit the bike so that they can ride efficiently without any more discomfort then tolerated and have the bike (which is more then just the frame/fork) track/steer/handle in a consistent and safe manor. But the rider, the builder AND the bike's parts (including tubes, lugs, shells, crowns) are never completely perfect. There will always be some deviation from the ideal. Tubing usually has some bow or non straightness when rolled on a flat surface prior to mitering as example and this bowing isn't always only in one plane (as in one butt transition can make the thick end bow up when the other butt causes it's end to go right).


Which brings me to a story about the perfect frame. When I attended the last east coast Eisentraut building class (1979 in Rutland VT) many of the students brought their work to Al and asked "is this right". After a few days one could see the frustration in his eyes as he repeated his advice/instructions over and over. Finally he stopped and brought us all together to say that there is a "good enough" point after which any more "improvement" makes no difference. He pointed to a student and said that he (the student) had one leg longer then the other, another had shoulders of different widths that most of our feet were slightly different in sizes. He then offered "find me a perfect person and I'll build a perfect frame". Which by then we understood was never going to happen and we went back to out work benches to try to find that "good enough" point in our work. Andy.

Unless you use one of those new-fangled external bearing bottom brackets.