should the BB and headtube be faced on a new steel frame?

on-yer-bike
Posts: 2,974
I have read different opinions on this. Can I trust my LBS to do it? I can't understand why its not done by the maker but I guess there is a reason.
Pegoretti
Colnago
Cervelo
Campagnolo
Colnago
Cervelo
Campagnolo
0
Comments
-
FWIW I don't buy any reason why you should have either done. Especially the head tube.
I've never had it done to any of my frames and have never had any problems with bottom brackets or headsets. I sort of have the opinion that facing them is a cure for a non existant problem.0 -
It is my assumption that every frame leaving a factory has been faced.0
-
These days frame tubes are turned in large volume on a lathe and will be far more accurate than the average facing tool in your LBS that's been abused by countless Saturday lads and bodger mechanics.Make mine an Italian, with Campagnolo on the side..0
-
Monty Dog wrote:These days frame tubes are turned in large volume on a lathe and will be far more accurate than the average facing tool in your LBS that's been abused by countless Saturday lads and bodger mechanics.
It doesn't matter how accurate a bb shell or head tube is before it's joined up, and it doesn't matter how accurate the TIG welding is or whaterver, the purpose of facing is to 'square up' either the head tube or bb shell after the joining process.
Granted, the accuracy of automated TIG welding machines in factories in the Far East these days probably means that the guy employed to do the facing has an easy time of things.0 -
I know of a couple of reasons to have it done, on a particular MTB headtube system with CK headsets, basically the headtubes were known to not be quite to tolerance and incredibly thick so would tend to deform the CK headset and cause premature failure.
I'd personally do it on any frame purely because headtubes tend to be reamed/machined prior to welding and I'd rather ensure the headtube is still spot on on arrival. However it is an utter minefield of headset 'standards' out there and you'll be buggered if you get the wrong one.0 -
ride_whenever wrote:I'd personally do it on any frame purely because headtubes tend to be reamed/machined prior to welding and e.
If we are talking about steel frames with straight gauge head tubes, then they are reamed after joining. As is the case with seat tubes.
But as stated previously, the accuracy of automated frame manufacture is that good these days, there is less need for reaming and facing.0 -
I sort of go with the idea that a bottom bracket shell doesn't require facing because
it's the threads that actually hold the BB in place and determine if things are in the right place. Facing the shell has no effect on whether the bearings go in right. They screw in until the shell(or part of it) stops them. No amount of facing will change anything about the way the bearings set in their final position. It's all about the threads. Crooked threads, crooked bearings.0 -
dennisn wrote:I sort of go with the idea that a bottom bracket shell doesn't require facing because
it's the threads that actually hold the BB in place and determine if things are in the right place. Facing the shell has no effect on whether the bearings go in right. They screw in until the shell(or part of it) stops them. No amount of facing will change anything about the way the bearings set in their final position. It's all about the threads. Crooked threads, crooked bearings.
Well, yes, but.... if the threads are cut correctly in the BB shell, but the faces aren't perpendicular to the axle line through the threads, you have a problem. More so if the faces aren't dead parallel too.
To the OP, no harm in checking, especially the BB. It may turn out to be a redundant check, but that's no reason to skip it altogether IMO.Open One+ BMC TE29 Seven 622SL On One Scandal Cervelo RS0 -
I sort of go with the idea that a bottom bracket shell doesn't require facing because
it's the threads that actually hold the BB in place and determine if things are in the right place. Facing the shell has no effect on whether the bearings go in right. They screw in until the shell(or part of it) stops them. No amount of facing will change anything about the way the bearings set in their final position. It's all about the threads. Crooked threads, crooked bearings.
However if the threads were badly cut then the bearings will never align correctly.He is not the messiah, he is a very naughty boy !!0 -
I wish you didn't have to think about whether your lovely new frame has to be faced or not, would be one less thing to worry about on build up ...0
-
Alignment of the bearings would be solely controlled by the threads *only* if there was no play whatsoever in the threads. In reality, there's play, and the BB shell faces are unlikely to be dead parallel without being faced. If the frame is metal, the shell will be deformed during the joining process - the only question is how much.
Whilst you can probably get away with facing neither, in the long term bearings should hold up better if the job is done. If you have a needle bearing headset it is imperative that everything is absolutely straight and square if you wish to be able to steer the bike.
Whoever said they assume everything is done right at the factory - you've obviously never worked in the bike industry! Some of the worst offenders have been prestigious Italian frame builders - these guys *never* did any prep on most of their frames back when steel was the material of choice. (Now that they're mostly coming out of Taiwan and/or China things may have improved, but I managed to remove quite a bit of alu from the shell on my current road frame a few years ago before it was right.)0 -
What about italian carbon frames ie top range ita-manufactured, or come to that matter, any carbon frame? Do they also need to be faced?0
-
I'm talking about a handmade Italian frame from a famous builder. Just can't think of a reason why they are not done before leaving the workshop. Isn't the wavy washer on Campag UT supposed to compensate for any discrepancies?Pegoretti
Colnago
Cervelo
Campagnolo0 -
If the frame has been bonded together then I would expect that the shell/insert will be either alu, and should have been machined square before being attached, or carbon. If it's alu it should be okay. If it's carbon, IMO it ought to be straight, but I'll admit here I know little about composite fabrication. I do wonder if attempting to face a carbon shell might in fact cut some of the fibres and thus potentially weaken things (?), but I'm not qualified to have an opinion about this.
I'd also be wary of assuming that because one thinks things ought to be okay, they actually will be. For instance, even if a Colnarello Ultra-Expensivo frame has an alu insert bonded into the carbon frame, the carbon might not be flat/flush, and it's quite conceivable that any "dags" could interfere with the BB cup fit. Note too that occasionally alu inserts can come detached from carbon frames, thus causing play and/or noises from the BB.0 -
I've heard two theories about why (in)famous builders didn't machine stuff:
1. They couldn't be bothered/ it's too expensive
2. Shops in Italy liked to feel like they were part of the process, and enjoyed doing the work
To be honest, the latter sounds like absolute b0ll0cks to me; us here in Australia looked on it as being sheer laziness, as well as requiring shops to have some very expensive tools usually only used by frame builders. We used to build frames and so had the tools, but the Japanese frames we imported never required their use; finish was always exemplary. Local custom builders would also normally take care of this themselves before letting things out their doors. It was only the Italian frames which had this problem, and the worst offenders by a long distance were Colnago. To be fair, I am talking about quite a long time ago, and I expect things changed considerably once they got feedback from people outside Italy - they certainly should have!0 -
Threads are machined into the BB shell before they're assembled into a frame - you'd have to go some way to machine a crooked thread on a modern machine tool - a worn thread cutting tool will be undersize not oversize too. That's not to say that BB shells can't be assembled incorrectly, but that would have no impact on the fit or function of the BB except you'd have wobbly cranks. A seperate issue is the need to ensure that the BB shell is the right length / within tolerance to get bearing pre-load correct which is where many people get confused about the need to face the shell i.e. remove resin or paint residue.Make mine an Italian, with Campagnolo on the side..0
-
^ If you're talking carbon frames then yes, any alu sleeve should be machined accurately and stay that way after bonding. If we're talking metal, the BB will be distorted after joining. The only question is "how much?" Using an expensive concentric BB tap set and then facing the BB is the only way to ensure the threads and shell faces are square on a metal frame - unless it's bonded together like some older alu frames. (And if I remember correctly, ALAN used to machine the BB threads *after* the frames were bonded together, and I don't think they were the only ones to do the machining post-assembly.)
If the bearing shell is not properly tapped and faced it is entirely possible for the BB cups to end up slightly out of parallel. This isn't a big deal with a conventional ("archaic") cup and cone BB, but with external bearings everything needs to be straight or bearing life will suffer badly. Facing the shell (and the headtube) usually means removing *metal* not just paint and/or resin; they are rarely as accurate as one might hope. The shell width shouldn't really vary much unless something very strange has happened. If it's a non-Heim joint crankset shell width doesn't matter much anyway, otherwise if it's Campag then that's what the wave washers are for, innit?0 -
satanas wrote:Alignment of the bearings would be solely controlled by the threads *only* if there was no play whatsoever in the threads. In reality, there's play, and the BB shell faces are unlikely to be dead parallel without being faced.
The threads on a BB are NOT course threads but very fine and anyone who has screwed the bearings in will know that "play" is pretty much non existant as it usually takes a wrench to even get them screwd in completely. Add to this the fact that when
the inside face of the bearing hits the BB shell this tightens up the threads even more and
assures that things are tight and secure. Even if the inside face of the bearing doesn't lay exactly flat against the shell it still causes the threads to "lock in place", thereby securing the bearing.0 -
Coarse as compared with what? In any case, I would respectfully suggest to you that perhaps the main reason (apart from lack of lubrication) that the threads are usually tight is that most metal BB shells are distorted to a greater or lesser degree; this comes with being heated up hundreds of degrees Celsius, then attached to other lumps of metal and being unevenly cooled. Don't believe me? Try tapping the BB shell with a proper professional BB tap (with two, concentric taps, joined by a central machined guide), then try screwing the cups in again. It will be noticeably easier.
The point of tapping and facing the shell is not to "secure the bearing" but to ensure that there is no misalignment between the LH and RH cups and the BB axle. While old-style cup and cone bearings are quite tolerant of misalignment cartridge bearings are not, and will suffer from premature wear if things are not straight. If all anyone cared about was preventing the cups coming loose, they could use loctite, epoxy resin, silicone sealer, etc. (Or just brute force.)0 -
satanas wrote:Coarse as compared with what?...........
Take a look at the threads on the BB(external bearing) and you'll notice that they are much "finer"(closer together - less deep) than, say, a nut and bolt that you have laying around the house. These fine threads offer a much more precise and secure
fastening, especially once they are tightened in place and the threads "lock" against each other.
One idea that I've seen that would seem to aleviate your fears of misalignment is the Rotor botttom bracket. It's bearings actually can move indside the cup to make up for any
misalignment that the threads may have.
To be honest I have never faced a BB and can't recall having any problems in that respect. In any case I'm not sure how you would prove that misalignment caused bearing failure unless it was so bad as to be visable with the naked eye.0 -
Dear American,
I have worked on this stuff professionally; I know what it looks like. I have seen bolts too. :roll:
I have tapped and faced BB shells. I am not making this up as I go along, but basing my comments on years of experience with this stuff. Of course, as I am not American it may well be that I am a moron/antichrist/ar$eh0le, etc, etc. Of course, since you are American it is to be expected that you will be patronising, whatever your level of knowledge (or ignorance). FYI, misalignment was a serious concern in the earlier days of external bearing BBs; maybe the shells are now better machined ex-factory, but I doubt it.
How does one "prove" anything, especially to somebody who does not wish to consider another point of view? Just asking... Consider religion - or the lack thereof - for example. See what I mean?
Have a nice day. :evil:0 -
So to sum it up without offending the Americans or us Brits,
Ideally our BB shells should have the threads re-cut and the faces machined flat but in the real world most of us don't bother and find it causes no problemsHe is not the messiah, he is a very naughty boy !!0 -
dennisn wrote:satanas wrote:I have tapped and faced BB shells.
I don't doubt that you have. You may do whatever you like. I'm only saying I don't believe it's necessary.
I suppose that you're free to believe what you want, but having faced a few BB's on new frames you would be wrong. If external bearings are used, then to avoid premature wear the shell should be faced. True, there are some new frames that don't require this and the last Surly LHT frame I equipped with external bearings did not require the BB to be faced. Many more frames do require this however.
I'm surprised that you admit never having done this job yourself but reject the experience of others who have done this. It takes all sorts I suppose.0 -
onbike 1939 wrote:dennisn wrote:satanas wrote:I have tapped and faced BB shells.
I don't doubt that you have. You may do whatever you like. I'm only saying I don't believe it's necessary.
I suppose that you're free to believe what you want, but having faced a few BB's on new frames you would be wrong. If external bearings are used, then to avoid premature wear the shell should be faced. True, there are some new frames that don't require this and the last Surly LHT frame I equipped with external bearings did not require the BB to be faced. Many more frames do require this however.
I'm surprised that you admit never having done this job yourself but reject the experience of others who have done this. It takes all sorts I suppose.
Just how does facing the BB shell prevent premature wear to the bearings? It doesn't help in aligning them because the alignment is determined buy the threads. You can face a BB shell all you want and it won't change the alignment of the bearings. They will be in as good or bad of alignment as the threads are. Facing is a solution to a problem that doesn't exist. Now I will grant you that possibly poor threading could be a problem but facing won't correct it. The threads on your BB bearing are going to follow the threads in the shell, right or wrong.0 -
Threads tapped perfectly well in non-parallel (to each other) and non-perpendicular (to the crank axle) will consequently be non-parallel and non-perpendicular. Result of that is the bearing cups not being parallel or perpendicular. Result of that is premature bearing wear.Ben
Bikes: Donhou DSS4 Custom | Condor Italia RC | Gios Megalite | Dolan Preffisio | Giant Bowery '76
Instagram: https://www.instagram.com/ben_h_ppcc/
Flickr: https://www.flickr.com/photos/143173475@N05/0 -
Ben6899 wrote:Threads tapped perfectly well in non-parallel (to each other) and non-perpendicular (to the crank axle) will consequently be non-parallel and non-perpendicular. Result of that is the bearing cups not being parallel or perpendicular. Result of that is premature bearing wear.
+1 ......I agree. The threads determine how "squared up" the bearings are in relation to the frame and each other. Out of line with each other = premature wear. Facing = no effect on this thread misalignment.0 -
dennisn wrote:Ben6899 wrote:Threads tapped perfectly well in non-parallel (to each other) and non-perpendicular (to the crank axle) will consequently be non-parallel and non-perpendicular. Result of that is the bearing cups not being parallel or perpendicular. Result of that is premature bearing wear.
+1 ......I agree. The threads determine how "squared up" the bearings are in relation to the frame and each other. Out of line with each other = premature wear. Facing = no effect on this thread misalignment.
If the threads are tapped square in non-parallel faces then the threads will not be parallel with each other.Ben
Bikes: Donhou DSS4 Custom | Condor Italia RC | Gios Megalite | Dolan Preffisio | Giant Bowery '76
Instagram: https://www.instagram.com/ben_h_ppcc/
Flickr: https://www.flickr.com/photos/143173475@N05/0 -
Ben6899 wrote:dennisn wrote:Ben6899 wrote:Threads tapped perfectly well in non-parallel (to each other) and non-perpendicular (to the crank axle) will consequently be non-parallel and non-perpendicular. Result of that is the bearing cups not being parallel or perpendicular. Result of that is premature bearing wear.
+1 ......I agree. The threads determine how "squared up" the bearings are in relation to the frame and each other. Out of line with each other = premature wear. Facing = no effect on this thread misalignment.
If the threads are tapped square in non-parallel faces then the threads will not be parallel with each other.
Threads are tapped at the factory. It's not up to you and I to do this. If the threads aren't
tapped correctly(at the factory) all the facing in the world won't correct it. I suppose you could order a frame without a tapped BB shell but I've never heard of it. I have heard of shops "chasing" BB shell threads to "clean them up" but that doesn't change how the threads were tapped at the factory. When you screw a BB into the shell it follows the threads. Nothing else. When it gets into the shell far enough, the inside surface of the bearing will touch the shell, either partially or fully, and stop. You then tighten it down and end of story. It still follows the threads, stops when it can't screw it in any further, and pretty much locks itself in place(the threads lock together). The threads are what guide it
and you have no control over them. Whether the inside face of the bearing and the outside face of the shell are in perfect or less than perfect alignment is not an issue that
affects bearing life. Once again the bearing is held in place by the threads, not the shell face.0 -
dennisn wrote:Threads are tapped at the factory. It's not up to you and I to do this. If the threads aren't tapped correctly(at the factory) all the facing in the world won't correct it.
FYI, threads are cut in BB shells either:
1. before the shell is assembled into the frame (most commonly) or
2. after the frame has been constructed (rarely)
As I have already stated ad nauseum, it doesn't matter how straight everything is when the shell is distorted by the welding process, or stray bits of adhesive, paint, etc are left after the frame is built.
Whatever you might choose to believe, *all* threads have some play in them.
The *ONLY* way to guarantee things are straight is to use expensive, professional tools to firstly, re-tap the threads and ensure they are in fact concentric, and then to use these now-aligned threads to face the BB using another tool.
Only after these operations have been performed can one guarantee that the threads and BB shell faces (and thus the bearinngs) are all correctly aligned.
The fact that you refuse to understand or believe this (or are incapable of doing so) does not change the facts.
I am not going to waste any more time on this, or you.0