I got a frame here that has some thread damage in the bb shell. Should my LBS be able re-thread that? How much should I expect to pay?

NOTES: It's already Italian. It's really not that much damage, just a few bent threads that prevent the cup from screwing in. I'd tap it myself if I had a tap.

A well equipped Pro shop should be able to cleanup the threads.
bicycle tools for the purpose keep the threads aligned precisely to each other
as they are cutting or chasing ,as it will be,,

Just remind them that it's an Italian BB, the thread tapping tool from Park has different taps avaliable, the most common is use will be the Englis / ISO, but they should also have the Italian one.

In fact, Italian threaded bottom brackets have been of the endangered species lists for over a decade, and I'd be surprised if most shops today made the fairly large investment in a pair of Italian threaded taps.

I might also note that re-tapping a thread with a damaged lead (first thread or two) is far more difficult than tapping a virgin thread. Normally to re-tap such a thread we start from the good end (ie, the back of the crank for a damaged pedal thread) allowing the tap to follow the old thread and extend it over the bad thread. This isn't an option with a bottom bracket.

In order for the new threads to perfectly mesh with the remaining good thread they both have to be phased identically. Unless there's enough good thread in the damaged section that you can reliably pick it up, you run the risk that the tap begin cutting out of phase and then follows that lead destroying the existing thread. The right way to do the job is to clean out the damaged section as a counter-bore so you can pick up the lead of the undamaged thread immediately.

So, since anyone who knows the proper way to do the job, and since only a thread or two is damaged, I suggest that you forgo retapping entirely and carefully file or Dremel away the worst damaged areas until you can get the cup to engage the remaining good threads. If more than two or three threads are damaged The job becomes much more complex and I suggest you carefully qualify whoever you bring it to because otherwise the odds are more than 50/50 that they'll do more harm than good.

This is emblematic of a common and growing mythconception throughout bike culture and beyond. That what separates a skilled professional and a layman is the lack of proper tools. You might as well say I'd remove my own appendix but I don't have a scalpel.

While the doctor analogy is a stretch, it illustrates my point. It isn't tools that define a pro, it's knowledge, skill and experience. The problem is that all to often people who don't know what's involved, have no idea how much they don't know. This kind of re-tap job is a perfect example.

I sold cutting tools to framebuilders for years, and taught their proper use, and consulted with builders in order to improve their efficiency. All too often I'd get a phone call asking for help in undoing damage caused when an inexperienced shop mechanic got in over his head, unaware of the pitfalls of certain jobs. Experience is a great teacher, and most are smarter the second time around, but it's usually cheaper to learn from someone else's experience.

Rant over.

Indeed it is. Consider the following:

1. "Experience lets you recognize a mistake when you make it again."
2. "Good judgment comes from experience. Experience comes from poor judgment."

Anyway, back to the OP. Since this is an Italian bb and further assuming only one side of the shell is damaged could the mechanic start the tap from the good side and run it all the way through the shell and out the damaged side? That would assure good threads guided the tap as it cleaned up the damaged ones.

Not a practical option. First of all not all taps are capable of going all the way across the BB, but even if they could a more serious issue arises.

Most BB shells are tapped simultaneously from both sides, not all the way through from one. That means that there's no assurance that the threads are phased as one continuous helix. It's a lesson Mavic learned decades ago with their first BB, which threaded in from one side. It worked great when tested on BB's they tapped (from one side) but was a disaster in the field when it encountered the more common unphased threads of production BB shells. It was quickly replaced with one with split threads then the threadless model.

If the shop has a tap short enough to disengage from one side before engaging the other, and if the BB shell, and tap handle allow it to go all the way across, that would be the best option, but both conditions would have to be met.

I remember there is a saying about assuming...

I've been doing various machining since I was in early high school, build robots from scratch (FIRST Robotics!!!), and was an engineering major (until I dropped out). Really, I can can clean up a couple bent threads...if I had a tap.

I'll take a better look at it an probably use a Dremel. The bent threads are set back and I don't want to file away the good threads at the start.

Thanks.

Wait a minute. If the bad threads are inside but the first few threads are good then you have no problems having a tap clean them up as it will get a proper start. FBinNY and I assumed (there's that word again) that the lead thread was damaged which would make starting a tap very problematic.

Note to FB: I thought my "solution" was too good to be true. Nice to know why.

Sorry, no offense was intended, nor I did assume anything about your skill or lack thereof. I used your statement as a jumping off point for generalized commentary about ownership vs. the skill to use them. But in fairness, I did that after offering practical advice on how to proceed.

BTW- if the first threads are good, than tapping is indeed practical, though probably unnecessary. If you have a steel cup, you can frind a notch in it for clearance, and use it as a chaser. If you have alloy cups, you'll have to either tap, chase or dremel out the damaged section because they'll destroy the cup's threads, possibly causing it to seize.

Oh, I wasn't offended. There is no way for you to know my skill level. Thanks all!

Indeed, that's the only way to tap English and Swiss shells, which have opposite threads on each side.

That's what piloted taps are for, and the pro-quality taps from Campagnolo, VAR, Park and so on are piloted. At Trek we had a pneumatically operated machine machine to chase the threads on the BB shells after brazing; the taps were piloted so it can be done by machine.

Returning to the OP's problem, he should seek out a high-end shop that has been in business for several decades, as newly established shops will likely only want to invest in English thread taps. Older shops may have retained their Italian/French/Swiss/etc tools and thus be able to service the OP's frame.

Another option would be to make a thread chaser from an old Italian thread cup:

Right, which is why I qualified my suggestion as only applicable to Italian (and French) bb threads which are right-hand on both sides and could be tapped in one continuous pass.

There is a difference between threads which are on a common axis and threads with a common lead.

To understand the difference assemble 2 nuts onto a bolt until they touch. Then back one off a full turn making a gap equal to the screws pitch, line up the hexes and put the assembly in a vice but not too tight. Carefully back the bolt out of one and tap it so as to push the other nut half the distance to the first. If you worked carefully the nuts will still be perfectly lined up with a gap equal to 1/2 the pitch.

Now tighten the bolt again, and you'll see that it has to push the 2nd nut back to the original separation in order for the screws helical thread to line up with that of the nut. It isn't a problem of the shaft being aligned, but the helix being in phase.

Now imagine if after changing the distance between the nuts, we tightened the vise, and ran a tap down using the first as a guide. The crest of the tap would enter the second nut 180° out of phase and methodically destroy all the thread.

Experienced machinist retaping a hole whose first threads are buggered start by counterboring out the damaged area so the tap is free to float and pick up the lead of the remaining deeper thread.

If you still don't see the issue, I suggest you drill a hole on a block of scrap, tap 1/2 way through from one side, then flip the block and tap half way through fro the other. Now try to run a screw down the hole and the problem will be obvious.

BTW- Italian, and French bottom brackets are like that block you tapped from both sides, because that's how they were made.

That's true, but really only an issue with cartridge BBs that expect to thread all the way through from one side to the other.

Very interesting. What make bb is that thing?

This is a good point. When I opened my shop, there was no question in my mind that we would need the English thread tools, and we've had them since day one. They're expensive, somewhere between $350-400 I believe (dealer cost). I've debated about investing in the Italian thread tool, but the truth is that in three years in business, you could count on one hand the number of Italian threaded bottom brackets we've seen. And one of them is on one of my own bikes. We will probably go ahead and get the Italian thread tool soon, the trend for us is that we are working on more high end bikes than ever, and we will need the tool.

I've seen a few posts on BF recently where posters say some bike shops don't have even the English thread bb chasing/facing tools, with the reasoning being that the tool is too expensive and that most bb's are already chased/faced. I completely disagree with this, we use ours very often, and would not consider ourselves a quality service shop if we couldn't chase/face an English threaded bb. With the popularity of external bearing bb's, it's essential to be able to face the shell if the the faces aren't parallel; I can't imagine not offering this service. In the big picture, the cost of the bb tools in a full service shop are not that big of a deal.

Pino Moroni, 70s vintage.

Where is the OP located? If you are in Dc metro I can tell you who can do it for little money. Shops tend to ask a lot (around here) for two reasons, they know nobody else could do it, and second they dont want to do the job so sometimes ask for stupid amounts of money for 10 minutes job.

I thought in the home made tap, just like that one long time ago, how does it works??

Op, where are u located? U can ask in CL also, people have the stuff at home or know somebody that is friend of a friend... you know. I would not pay more than 40 bucks just in case.

I heard about these ones yeaaaaars ago, interesting.