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I need a machinist(23 posts)

I need a machinistshirt
Oct 25, 2002 9:23 AM
Refrain:
The Italian threads in my bottom bracket shell are crooked. Because of this it is impossible to mount a creakless bottom bracket.

I have heard of a process where a machinist will bond a sleeve into the shell and then machine it out properly.

I found a guy in the Chicago area who does this, but it turns out he's dead.

Does anybody know of any machinists anywhere in the U.S. who know how to do this?

Thanks!

/shirt
Confirm the problem firstCalvin
Oct 25, 2002 9:47 AM
A clever machinist can do many things, but you may want to first confirm that this is the issue. It is pretty difficult to have "crooked" threads in a shell. It is possible the outer surfaces of the shell are not square, and may need facing. That is a different process, however.

Whay type of bottom bracket is this? Is it a cartridge type? Creaking is the result to two things rubbing or moving. The common cause of a bottom bracket creak is simply that it is not in tight enough.
Already covered this beforeshirt
Oct 25, 2002 10:58 AM
I'm 99.9% certain that the problem is as I've described. The outer surfaces have been faced to each other perfectly. When you thread in the drive-side portion of the bb and then mount in the spindle, it's noticeably off-center from the other side. All three mechanics (good ones) at my LBS have spent quite a bit of time proving to each other that this is the problem.

It's not pretty difficult to have crooked threads in the shell when the shell is in a Ciocc. :-)
SuggestionNessism
Oct 25, 2002 12:27 PM
Find a framebuilder to do the repair. Most can take care of a problem like this. Assuming the frame is made of steel, the threads can be filled with brazing material and then rethreaded. For Al or carbon, you may be SOL. One bail out method is to find a shop/framebuilder that has some of the old Mavic bottom brackets since these install without threads.

To find a framebuilder in your area, you might want to post a message into the Framebuilders list.

http://www.phred.org/mailman/listinfo/framebuilders

Good luck.

Ed
I also don't think the threads are crookedspookyload
Oct 26, 2002 9:33 AM
If you see how threads are cut into a bb, the two tools used can't go in crooked from each other. If one side was crooked, the other side would be two. The only way this could have happened was if you tried to force a bb into the shell cross threaded when you installed it the first time. I have seen this when a customer replaces the BB on an aluminum frame themselves and cross threads it and trys to force it in. The best chance here is to try and chase the threading out and hope you can get it to line up straight this time.

If the frame was new when you first discovered it, send it back under warranty. Ciocc should fess up if it is there problem.
Maybe Luigi with a bottle of wine in him on a Friday?SnowBlind
Oct 28, 2002 8:46 PM
"Mama Mia! I'ma gonna need a bigger hammer..."
Look at the BB, not the frame?Kerry
Oct 26, 2002 11:06 AM
The chances are that your BB (the component, not the frame) has gotten it's threads damaged or worn such that it cross threads itself. Check this with a new BB. If your frame is cross threaded through damage, it should be visually obvious.
No. FOUR bb's all do the same thing. No x-thread either (nm)shirt
Oct 26, 2002 6:05 PM
Those damn ItaliansREPO42
Oct 27, 2002 2:56 AM
I have heard nothing but grief with italian threaded BB...Italian threaded BB tend to creak a lot, and loosen even more. And if that's not enough they way overprice there frames(Colango, Bianchi). If you are determined to machine out the BB, then is possible to re-thread it to English threads? I am by no means a bike Guru, but I don't think I would ever get a frame with Italian threads...Lets face it they have only mastered salad dressing...No offense Italians, you guys have some HOT women....
Those damn ItaliansTom C
Oct 27, 2002 1:40 PM
salad dressing and along with the Greeks mastered and largely authored western civilization. By the way, Italian BB on my 20 year old Rossin and no problems.
Stronglightcurlybike
Oct 27, 2002 3:04 PM
is making the bb that Mavic used to make. It slides into the bb shell and uses a nut on each side to retainn the cart. It does require that you get your shop to use the Mavic tool to prep the shell. Also, they are only using square drive bb axles, no spline. You may want to do a websearch to find the US supplier.
Conversion kitNessism
Oct 27, 2002 7:24 PM
Bringheli.com sells an insert that is used to convert an Italian threaded bottom bracket shell to english threads. The insert is already threaded on both sides so there is no need to re-thread after installation. You should be able to glue the conversion adapter into the frame using JB Weld or similar.

Good luck.

Ed
sure about that??C-40
Oct 28, 2002 3:19 PM
English threads are 1.370 and Italian threads are 1.417 (36mm). That's only a difference in .0235 inch per side (like heavy shim stock). The threads have to be deeper than that. If such a conversion is made, it has to be to something smaller than 1.370.

Also, if you thread an adapter into a crooked thread, it will still be crooked.
Hey C-40REPO42
Oct 28, 2002 9:22 PM
What do you do for a living? You have some pretty technical answers. Do you own your own bike shop, cuz if you do and it's close to reno, then I'm there!
mechanical engineer & machinist...C-40
Oct 29, 2002 7:24 PM
I work at the only remaining plant that manufactures mechanical nuclear weapons components. Honeywell FM&T, Kansas City, MO. I worked 10 years as a machinist prior to and during my college years. Bikes are a hobby.
....and....grzy
Oct 30, 2002 5:37 PM
...bombs are your passion? ;-b
Very sureNessism
Oct 29, 2002 1:37 PM
Joe Bringheli sells framebuilding parts and Dedacciai tubing. His main lug supplier, Walter, makes the adapter and the wall thickness is quite thin as you noted. They make it so builders can change an Italian threaded bb shell to BSA. In fact Walter discontinued one of their more popular BSA threaded bottom bracket shells so builders either have to sell the frame with Italian threading or install an adapter. Needless to say, some of the framebuilders that have been using the Walter BSA shell are not happy.

As far as installing the adapter is concern, it should be fairly easy to straighten the threads with a bottom bracket tap set. I assume the threads are buggered some at this point causing the noise issue. The adapter will likely wobble some in the buggered threads but if it is carefully brazed or epoxied in place, it should be OK.

Ed
don't think so...C-40
Oct 29, 2002 7:18 PM
If you measure the minor diameter of an Italian BB thread you'll find that it's few thousandths of an inch larger than the major diameter of an english BB thread. There is no way to manufacture an adapter that's threaded internally and externally with a wall thickness that's less than zero, or even just a few thousandth's of an inch thick.

I'd have to see this to believe it. Perhaps the BB could be bored to a slightly larger diameter and an threaded sleeve glued in, but even then the wall thickness would be extremely thin.

As for straightening a crooked thread, I'm afraid that you're too optimistic. If a tap if used to chase the threads, it will follow the original path. A tap only cuts once, you can run it in and out all you want. No metal will be removed.
With all due respect...Nessism
Oct 29, 2002 9:24 PM
I held the adapter in my hand a few months ago so I can assure you that it does exist. Walter makes some pretty nice components so I don't think he is making junk here - although as I stated before, many of the framebuilders that like his shells are not happy about him forcing the builders to buy the adapter. I suggest you call Joe Bringheli if you don't believe me. He might tell you that the adapter is a pain and he is not happy with Walter, but he also will tell you that it does work. Tell him that Ed Ness told you about it. He is a really nice guy and very helpful.

As far as the threads are consern, a bottom bracket tap set has a long guide pin so it is impossible to thread the shell crooked if the tool is used correctly. It is fairly common for a bottom bracket to go in crooked which will crossthread the threads in the shell - I have done this before myself. The threads can be straightened, out using the proper tool, but some will be lost in the process which will cause the bottom bracket to wobble slightly in the shell - often resulting in noise. A few missing threads will not be a big deal since the adapter will have to be glued or brazed in anyway.

I'm not trying to sound like a know-it-all but as a hobby I have brazed together a few frames before so I'm not totally full of crap here. BTW, none other than Richard Sach uses a Walter bottom bracket shell for some of his frames. My understanding is that he has played around with the adapter so you might even shoot him a message if you want further information.

Ed
likewise...C-40
Oct 30, 2002 5:14 AM
No disrespect intended, but if the thread dimensions overlap, the "adapter" would consist mostly of air. If the root of smaller thread overlaps the the crest of the other, there is no material left to machine. I've not been able to get the exact root and crest diameters, but I'll see if I can find them.
Last thoughtNessism
Oct 30, 2002 7:31 AM
Just a guess here but maybe Walter undersizes the BSA interior thread depth/height slightly to make the adapter hold together for installation purposes. I would think that most builders would braze/glue the adapter in place and then chase the threads to make sure everything is alighed and the threads are at full depth. Not really sure...but I am sure the adapter is available.

Ed
Just a matter of indexing, put the crest under the crest, yeahcurlybike
Oct 30, 2002 4:30 PM
With all due respect...e-RICHIE
Oct 31, 2002 5:11 AM
the conversion rings work fine for both new frames as well as for frames w/italian threads that are past their 'sell-by' date. they are amazing little feats of machining. i was skeptical until i saw them in person.

e-RICHIE

richardsachs@juno.com