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Thread: alignment table/build surface tolerances

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    Default alignment table/build surface tolerances

    I've been shopping around for a decent surface plate or alignment table for a surface jig I have. What sort of tolerances are generally necessary/acceptable on a table for frame building? I have a friend who has a fab shop and we've been talking about building something interesting ourselves but we're not sure of the tolerances we need to be within. The various surface plates I've looked at have pretty incredible tolerances, but then I hear stories about alignment tables at various factories having tolerances with +/- multiple millimeters. That's far from the thousandths that most surface plates seem to be (granite or otherwise).

    I recall e-richie saying something about his measurements being only reproducible on his alignment table, which was also the story at UBI (same model of table I believe) and in a lot of cases you couldn't even duplicate them consistently if you sat there all day flipping the frame around. When all was said on my first frame I was somewhere within 1-1.5mm of runout when I put it on the table. That was averaged out over a few times of taking it on and off the table and that's assuming the table was accurate. After fitting up the bike it seems a ton straighter than anything else I've ever owned.

    Anyway, just curious what the opinion here is. And yes, buying a chunk of granite would be easier, but where's the fun in that? :)

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    sam
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    Default Re: alignment table/build surface tolerances

    I dont have a direct answer for you, but a general answer would be as flat as possible, if my standoff/bb tower, etc. say is built .005 off, and the table where it sits is .005 off, i might now be .01 off, and .01 across a 56cm tube can add up to a fairly big number. so not only does the table have to be flat but everything in the process does, as the numbers stack up. I see alot of shop made tables that look nice but in time are going to warp, so if you dont have the experience in building a precision table you are better off buying one.

    That being said, I have also seen some tables from some respectable builders that I can see are also not the best tables,but they know how to work with what they got so it dont matter as long as the frame is straight, so in some thoughts people play to much into how flat there tools are. But if you are going to do it do it right, but I think you are going to have a hard time getting someone to say here this is the number.

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    Andrew R Stewart's Avatar
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    Default Re: alignment table/build surface tolerances

    Sam touches on one of the issues that i've had with discussions about frame alignment. People are quick to throw out numbers but few place said numbers in a frame of reference that is needed to make full sense what the number means. So a .005" offness is what? Is this over a few inches of the Bb post base or is this along 10" of seat tube or across 20" of a head tube alignmeng bar? Major differences here in real life applications.

    Another aspect that is less often talked about is the precision of the tubes themselves. Ever roll out or measure diameter over the length of a tube? Then after brazing you can see distortions in tube diameters close to the joint. So where do you start the measurement? If you're using a BB face as the starting point (as on a whipping post) what about it's distortion (that much has been said about). Just because with a dial indicator you can see .001" difference is no reason to think it is an important amount.

    I try to get a picture to the precision of the tubes first and realize that I'm not going to get much better then this limit. I measure alignment a few times on each side of the bike to further get a feel for the frame's center line alignment. Currently i hold the frame by the shell on a post (but soon to go to a head tube held method) and measure the HT to the plate and then the ST to plate over the same length. This way i seperate out the shell's alignment from the frame's tracking alignment. Over the same length of HT/ST i try for .015" of difference or less, this length is usually 9"-12".

    Maybe as important to any ultimate alignment is the ability to be consistant in how you measure and then to be able to repeate to a degree the measurement. When I had my own shop I would do a number of Winter overhauls, most of these bikes got a measuring session on my plate. Not so much to sell another service, backed up by numbers (and who can argue with a number?) but more to add to my personal data bank and learn how setting up the measurement can effect the read out. You'd be impressed how off so many frames are and the rider never knows it.

    So some of your answer (to the not directly asked question) is that you have to build an understanding as to what's enough, alignment wise. Your surface plate needs to be at least as good as this personal tollerance limit and it has to be stable enough to be able to repeate the measurement (with in some reason). If your plate is off by more then your personal tollerance limit then you need to know that and know how to accomidate that.

    So there's no one answer that we all will agree with. But then you knew that. Andy.
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    Default Re: alignment table/build surface tolerances

    Quote Originally Posted by Andrew R Stewart View Post
    So there's no one answer that we all will agree with. But then you knew that. Andy.
    Yeah, I think I knew that already too :)

    I heard a story when I was out in Oregon about one of the alignment tables at a rather big bike company reading that the table itself was something like 5mm off so who knows how off the frames ended up being.

    Something I've had emphasized to me by other frame builders is that these are 'hand' built frames and there's only so much you can do to overcome the nature of the material and the process (mainly, heat). I guess I need to figure out what that personal tolerance is and build accordingly.

    I should also stop over-thinking this whole thing and start another frame.

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    Default Re: alignment table/build surface tolerances

    Quote Originally Posted by prolix21 View Post

    I should also stop over-thinking this whole thing and start another frame.
    It may seem counter-intuitive and counterproductive, but this ^^ is exactly what you should do atmo. The very task of building a frame - learning to attach pipes to other pipes - as well as the design parameters you work with (fit, handling, clearances for components...), should be your focus. If you don't know, don't learn, or can't do these first, all the precision in the world is worthless. There are a lot of really nice (and heavy, and large...) systems being shown on several boards and I think the fellow(s) with the torch and files is/are putting carts before horses.

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    Default Re: alignment table/build surface tolerances

    Putting asside the question of frame building best practice (I'm a machinist, not a frame builder) flatness tollerance is one of those things where if you have to ask, you probably won't know what to do with the answer either. I'm not saying this to belittle anyone, just saying that the information has little utility to anyone without access to a metrology lab.

    Flatness is the measured deviation of a surface from a perfect plane. A flatness tollerance is the distance between two parallel planes encompassing every point on the surface. In order to inspect for flatness, you need a plane (approximate, of course) that's as big as or bigger than the surface being inspected.

    All of this being said, knowing the flatness tollerance of a surface plate still tells you very little about the possible margin of error when measuring on it because it says nothing about the distribution of those high and low points. Add to that the variability in shape and size of the instruments and parts that come into contact with it and you see why it's hard to say what degree of precision is required.

    And in case this post wasn't anal enough, runout is used to mean only the deviation of a circular feature from a part's reference axis.

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    Default Re: alignment table/build surface tolerances

    Quote Originally Posted by e-RICHIE View Post
    It may seem counter-intuitive and counterproductive, but this ^^ is exactly what you should do atmo. The very task of building a frame - learning to attach pipes to other pipes - as well as the design parameters you work with (fit, handling, clearances for components...), should be your focus. If you don't know, don't learn, or can't do these first, all the precision in the world is worthless. There are a lot of really nice (and heavy, and large...) systems being shown on several boards and I think the fellow(s) with the torch and files is/are putting carts before horses.
    so true mr sachs...

    in motor sports ...,
    building a road racing vehicle means understanding chassis and suspension --- if brute horsepower is your main stroke, the drag strip maybe your calling card..,
    your horse "without the cart.."

    ronnie

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    Default Re: alignment table/build surface tolerances

    Quote Originally Posted by e-RICHIE View Post
    It may seem counter-intuitive and counterproductive, but this ^^ is exactly what you should do atmo. The very task of building a frame - learning to attach pipes to other pipes - as well as the design parameters you work with (fit, handling, clearances for components...), should be your focus. If you don't know, don't learn, or can't do these first, all the precision in the world is worthless. There are a lot of really nice (and heavy, and large...) systems being shown on several boards and I think the fellow(s) with the torch and files is/are putting carts before horses.
    In some ways I think my first frame experience put the cart before the horse. I certainly learned a lot at UBI and I walked away with what I consider a successful frame. It's solid, straight and everything fits fine, but I wish I had struggled more and in some ways I wish I would have fallen on my face a few more times than I did. Perhaps more to the point, I wish I hadn't learned with such great tools and such accurate fixtures. I feel like I skipped ahead and lost something in the process and now I'm sort of reverse engineering things and trying to build frame number two by forgetting all the tools and crutches I had on frame 1. I'm probably learning more through this process, and will no doubt learn a ton more by the time I complete frame 2, but its hard not to think that an anvil jig would cure all my woes.

    Part of the reason I'm going with a flat plate fixture is to get a more basic/manual process and a feel for how it all fits together.

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    Default Re: alignment table/build surface tolerances

    Quote Originally Posted by prolix21 View Post
    In some ways I think my first frame experience put the cart before the horse. I certainly learned a lot at UBI and I walked away with what I consider a successful frame. It's solid, straight and everything fits fine, but I wish I had struggled more and in some ways I wish I would have fallen on my face a few more times than I did. Perhaps more to the point, I wish I hadn't learned with such great tools and such accurate fixtures. I feel like I skipped ahead and lost something in the process and now I'm sort of reverse engineering things and trying to build frame number two by forgetting all the tools and crutches I had on frame 1. I'm probably learning more through this process, and will no doubt learn a ton more by the time I complete frame 2, but its hard not to think that an anvil jig would cure all my woes.

    Part of the reason I'm going with a flat plate fixture is to get a more basic/manual process and a feel for how it all fits together.
    Re boldfaced ^-
    They showed you how to make a frame, not how to build frames, or how to become a framebuilder atmo.
    Happy to answer all questions or just offer opinions...

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    Default Re: alignment table/build surface tolerances

    Quote Originally Posted by ron l edmiston View Post
    so true mr sachs...

    iif brute horsepower is your main stroke, the drag strip maybe your calling card..,
    your horse "without the cart.."
    ronnie
    eh...
    Brute horsepower wont get you far on the drag strip either if you want more than to beat the next idiot. If you actually want to be good at something you are going to have to know the whole package, even on the drag strip, chassis will get you hooked up and running strait, (as opposed to into the wall).

    I have no idea what the masters are talking about here, what is really involved in the art of building a magic frame, but I do know that mastery is far deeper in this special place than just accuracy. 'was happy to be a spectator to this until the drag strip comment.
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    Default Re: alignment table/build surface tolerances

    This is exactly why i feel that to get the most out of a class you should have built a frame or three. I have had this discussion with at least one teacher who dissagrees with me. he feels that trying to correct poor torch handling is harder then teaching with a freash slate. Perhaps so for the torch work. But making a frame is so much more then brazing effectively.

    My first class (of any real sense) was after 6 frames. I know I came away with so much more neuance and focused understanding then the other 7 studients did. My second class was 20+ years later, 30+ frames. The teacher tried to get me to move the torch differently then i was use to. Well this old dog didn't learn that new trick but I did refine other elements of building.

    I agree with Richard that taking a class is great to get a frame that you've built (largely..) yourself. But learning how to trouble shoot, solve problems, make mistakes and try other approaches is not the main focus of a two week class. Andy.
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    Default Re: alignment table/build surface tolerances

    Starting to touch on a subject I debated on about taking the Frame-building class first or after several attempted frames in order to gain more "aha!" moments. If I didn't understand the problem I was trying to solve, I thought it would just go over my head and not sink in. It would be most ideal to take Two classes! One to get started, one to clarify:)
    So far, I'm still slowly struggling through bike #5, keep making mistakes (opportunities for improvement) and really ready to take that class!
    Thanks for sharing your experience prolix21, and Andy also.
    cheers
    andy walker

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    Default Re: alignment table/build surface tolerances

    Quote Originally Posted by afwalker View Post
    Starting to touch on a subject I debated on about taking the Frame-building class first or after several attempted frames in order to gain more "aha!" moments. If I didn't understand the problem I was trying to solve, I thought it would just go over my head and not sink in. It would be most ideal to take Two classes! One to get started, one to clarify:)
    So far, I'm still slowly struggling through bike #5, keep making mistakes (opportunities for improvement) and really ready to take that class!
    Thanks for sharing your experience prolix21, and Andy also.
    cheers
    andy walker
    I think after I get a half dozen frames under my belt I'd like to go back and do a one-on-one class with someone. My UBI class actually turned into a lot of one on one with Ron and Keith as our class was super small, but I could see a lot of value in working with someone once I've done a half dozen frames and have a better feel/comfort level. UBI's two weeks are a bit of a blur.

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    Default Re: alignment table/build surface tolerances

    The value of getting the right start with an experienced teacher goes beyond not having to unlearn bad habits. It also includes frustration management and effective use of time and resources. The average student that attends my class doesn’t have anywhere near enough skills or knowledge to make a frame by himself. It doesn’t make any sense for them to be bumbling around on their own wasting time, resources and emotional energy trying to figure out what to do and how to correct what they did. Most likely they will just get frustrated and give up. A skilled instructor explains and demonstrates proven methods and gets a student right by tough patches so they can continue to build on their successes.

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    Default Re: alignment table/build surface tolerances

    Quote Originally Posted by Doug Fattic View Post
    The value of getting the right start with an experienced teacher goes beyond not having to unlearn bad habits. It also includes frustration management and effective use of time and resources. The average student that attends my class doesn’t have anywhere near enough skills or knowledge to make a frame by himself. It doesn’t make any sense for them to be bumbling around on their own wasting time, resources and emotional energy trying to figure out what to do and how to correct what they did. Most likely they will just get frustrated and give up. A skilled instructor explains and demonstrates proven methods and gets a student right by tough patches so they can continue to build on their successes.
    Totally agree with this, and it describes just about everyone in my class. None of us could have just walked in and built a frame. My issue now is applying that knowledge outside the classroom without all the benefits of the tools they taught us on.

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    Default Re: alignment table/build surface tolerances

    Quote Originally Posted by prolix21 View Post
    Totally agree with this, and it describes just about everyone in my class. None of us could have just walked in and built a frame. My issue now is applying that knowledge outside the classroom without all the benefits of the tools they taught us on.
    Relentless repetition atmo.
    Don't even try to build frames.
    Fab a few dozen joints, or dropout confluences, or sub-assemblies.
    Heck - do a hundred.
    Lather, rinse, repeat.

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    Default Re: alignment table/build surface tolerances

    Quote Originally Posted by e-RICHIE View Post
    Relentless repetition atmo.
    Don't even try to build frames.
    Fab a few dozen joints, or dropout confluences, or sub-assemblies.
    Heck - do a hundred.
    Lather, rinse, repeat.
    I feel this. It's a rare cat today who can shape his life to one of the few production jobs, but considering its probably the best way to learn I don't know why more folks don't try to emulate it. $50 of 1" and 1.125" 4130 will make enough practice slip fit lugs to fill a 5 gallon bucket. $20 of 5/8" 4130 and some hardware store mild steel will make bunches of tabbed dropout assemblies. That's cheap but effective practice and ideally should be done many times over.
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    Default Re: alignment table/build surface tolerances

    I don't think practice is advocated enough, probably because it wasn't the traditional way to learn. I've brazed over 1000 frames and I still go and practice on scrap sometimes.

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    Default Re: alignment table/build surface tolerances

    As this thread drifts...

    I'll place my vote for practice loud and clear. I just had one of the worst sessions of brazing that I've had in a while. Partly because i don't torch routeenly and partly because i don't...

    I am reminded of the interviews of the musians i've heard (usually on NPR) and their, to the person, claims of the need to keep their chops up with practice. Andy.
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    Default Re: alignment table/build surface tolerances

    Quote Originally Posted by EricKeller View Post
    I don't think practice is advocated enough, probably because it wasn't the traditional way to learn. I've brazed over 1000 frames and I still go and practice on scrap sometimes.
    I'm not sure I understand that first question. What tradition doesn't emphasize practice?
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