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Thread: Fork questions

  1. #1
    veryredbike is offline VSalonistas
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    Default Fork questions

    I'm going to start building my first fork this month (after I get my second frame painted), but I have a few questions:

    1) If I'm using socketed dropouts and a lugged crown, can I use 56% silver for everything? (The dropouts are Dazza's stainless, if that matters)

    2) I'm a little nervous about the blind braze from the legs into the crown. my plan was to pin it and then watch the pins to ensure that I'm getting real penetration. Does that make sense?

    3) Anything you guys wished you'd known when you made your first fork?

  2. #2
    Eric Estlund's Avatar
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    Default Re: Fork questions

    Buy three sets of fork stuff. Cut the first one apart to make sure it works. Build fork with second set, and have the third for another fork or as back up in case you munch the second set. 56 could work for everything depending on the fit up. Make sure you are buying parts made to play well (ie fork tips fit with blades fit with crown).

  3. #3
    Andrew R Stewart's Avatar
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    Default Re: Fork questions

    VRB- Eric gives great advice! To insure complete fill with the blind socket I have tried a ring of filler placed inside without sucess in getting it to flow out (preceeded to fill the usual way, and there was no rattle so probably got a little melt). A few other times I placed a pin very deep (at the base of) the socket and have gotten flow to the pin. Take care in how the drop outs are aligned prior to brazing. If ther're a bit off from the blades when you tighten up on a QR or jig axle bolt things can shift. I'll tack the inside and outside points first then braze starting on the inside of the blade/crown where the material is the greatest. I'll usually do the steerer/crown in brass as a sub assembly. Andy.
    Andy Stewart
    10%

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    Eric Estlund's Avatar
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    Default Re: Fork questions

    Just to follow part of Andy's comment- I use bronze for most things these days. While you can certainly use 56 for a well fitting crown/socket drop out set up, you could also use bronze if you preferred.

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    veryredbike is offline VSalonistas
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    Default Re: Fork questions

    Man, I HATE it when people give good advice that means slowing down ;-)

    Roger, I'll grab a cheap crown and blades to practice with when I get the tubing for the next frame. Hell, maybe I'll be lucky and can snag a blem or two for cheap from someone to play with.

    If I use silver, can I still do the crown and stearer as a sub-assembly and then follow up with blades later? It's a full slope fork, and I think I can heat up the sockets for the blades without re-melting much around the steerer, but would love to hear if that's a bad idea.

    Thanks as always for the help, guys!

  6. #6
    Daltex's Avatar
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    Default Re: Fork questions

    Quote Originally Posted by veryredbike View Post
    Man, I HATE it when people give good advice that means slowing down ;-)

    Roger, I'll grab a cheap crown and blades to practice with when I get the tubing for the next frame. Hell, maybe I'll be lucky and can snag a blem or two for cheap from someone to play with.

    If I use silver, can I still do the crown and stearer as a sub-assembly and then follow up with blades later? It's a full slope fork, and I think I can heat up the sockets for the blades without re-melting much around the steerer, but would love to hear if that's a bad idea.

    Thanks as always for the help, guys!
    Silver will work great, if your lug/tube fit is not too sloppy.

    Yes, build your steer tube and crown as a sub-assembly. I also then build the blades and dropouts as a sub-assembly.

    Destructive testing is ideal +1. Repetition will help you improve.

    I am sure you know but I will repeat, don't use bronze on stainless steel fittings.

    Good luck.
    Glenn Thompson
    http://Daltex.bike

  7. #7
    JuanGrande is offline VSalonistas
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    Default Re: Fork questions

    I just finished my second fork on Friday night... and raced in CX this morning (So take what I say with a grain of salt). To echo the previous comments, I built using sub-assemblies. steer tube to crown, dropouts to fork legs, and then legs to crown. I had really good fitment, so 56 silver all the way around. Two things to mention that weren't discussed above; 1) add filler at one point and try and get it to wet out/pull through to other parts of the socket, and 2) don't cook it (i.e. use good heat control... easier said then done sometimes).

    What I learned on this fork build - take it slow, and if things don't look right, pull it apart and fix it before you braze. Jigs are wonderful things but they don't solve fitment issues even if it looks right in the jig. Again, take it slow.

    JC

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    devlin's Avatar
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    Default Re: Fork questions

    Love these threads.
    "Even my farts smell like steel!" - Diel

    Sean Doyle

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    Curt Goodrich is offline VSalonistas
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    Default Re: Fork questions

    Why are people brazing the steerer to the crown as a sub-assembly? I've never understood the rationale. Is there one? I'm not trying to stir the pot. I'm being sincere.
    Last edited by Eric Estlund; 11-19-2012 at 11:27 AM. Reason: oops
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    Eric Estlund's Avatar
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    Default Re: Fork questions

    I do it so that I a) have a "handle" to hold onto for crown shaping and b) it fits in my set up for drilling the brake hole better without legs. If one wants to turn the race seat on a lathe it also saves having those long legs whipping around. It's not at all necessary from a brazing order perspective.

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    Daltex's Avatar
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    Default Re: Fork questions

    Quote Originally Posted by Curt Goodrich View Post
    Why are people brazing the steerer to the crown as a sub-assembly? I've never understood the rationale. Is there one? I'm not trying to stir the pot. I'm being sincere.
    Everything Eric said, plus 'fewer moving parts'.

    Many folks jig up the entire fork as seperate pieces, and braze everything at once. I prefer to do each operation seperately to focus on it, isolated from the rest of the fork. FWIW.
    Glenn Thompson
    http://Daltex.bike

  12. #12
    jon_norstog is offline VSalonistas
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    Default Re: Fork questions

    Quote Originally Posted by Curt Goodrich View Post
    Why are people brazing the steerer to the crown as a sub-assembly? I've never understood the rationale. Is there one? I'm not trying to stir the pot. I'm being sincere.
    Curt, list:

    I braze the steerer and crown first because I don't have a lathe or crown race cutter. I do forks in batches and take them to a local machine shop to have the races cut. They have a $50 minuimum for setup plus an hourly, so if I take a single crown it costs $65. But in batches it runs about $15, except for stainless.

    First fork I made I took it in with the legs on - it cost me $150 to get the crown race cut! Live and learn.

    I have had no problems with a silver-brazed steer tube coming loose when brazing in the legs. Just be mindful ....

    good luck!

    jn


    "Thursday"

  13. #13
    Curt Goodrich is offline VSalonistas
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    Default Re: Fork questions

    Quote Originally Posted by Eric Estlund View Post
    I do it so that I a) have a "handle" to hold onto for crown shaping and b) it fits in my set up for drilling the brake hole better without legs. If one wants to turn the race seat on a lathe it also saves having those long legs whipping around. It's not at all necessary from a brazing order perspective.
    I get what you're saying about having a handle unless one has a lug vise. I do not understand how the fork blades could interfere in the drilling process. As far as turning the crown race on a complete fork with the lathe it's a non-issue unless the lathe is quite small.

    To me, brazing the steerer in as a sub-assembly is a work around for a lack of equipment and/or poor fixtures. There's no shame in that. But if one has the equipment, why not save a little time, save some gas, and save the casting from another heat cycle? Seems like a win win situation and a no brainer to me.
    Curt Goodrich
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    Daltex's Avatar
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    Default Re: Fork questions

    Just curious, do you braze on the dropouts to the chainstays at the same time you're brazing the chainstays into the shell? I am being sincere, not snarky.

    I can list reasons why I braze the steerer to crown, but the biggest reason in thats the way I've always done it. On my next fork,I will try doing the steerer/crown/blades at same time.
    Glenn Thompson
    http://Daltex.bike

  15. #15
    Eric Estlund's Avatar
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    Default Re: Fork questions

    Quote Originally Posted by Curt Goodrich View Post
    I get what you're saying about having a handle unless one has a lug vise. I do not understand how the fork blades could interfere in the drilling process. As far as turning the crown race on a complete fork with the lathe it's a non-issue unless the lathe is quite small.

    To me, brazing the steerer in as a sub-assembly is a work around for a lack of equipment and/or poor fixtures. There's no shame in that. But if one has the equipment, why not save a little time, save some gas, and save the casting from another heat cycle? Seems like a win win situation and a no brainer to me.
    I have a lug vise. Works great. I prefer my method.
    My drilling set up is such that the legs bump into my drill column. Could I change that? Sure, but again, my method works well for me.
    Will spinning legs be an issue? Doubtful, but it's also nice to not have all of that going on. Yes, I've done many both ways.

    No worries Curt- we do it in a different order. I have a process that works for me, and as you say, I feel no shame in that. Different strokes, and we both seem to build good forks.
    Last edited by Eric Estlund; 11-19-2012 at 03:15 PM. Reason: I added more because I couldn't help myself

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    Default Re: Fork questions

    I braze my crown and steerer as a sub assembly too. Main reason is I like to turn down the race on my lathe and my tiddly wee Myford isn't big enough if the blades are on. Also, I only use a couple of different crowns so if I have few builds coming up, I'll braze a bunch of crowns to steerers in advance, turn down the race and sometimes mill the brake hole even if I don't know what blades or dropouts I'll be using. It's a small thing but if I'm setting up the lathe to turn races or setting up the mill for brake holes, it's more efficient to do a few.

    Steven
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  17. #17
    Curt Goodrich is offline VSalonistas
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    Default Re: Fork questions

    Quote Originally Posted by GAAP View Post
    Just curious, do you braze on the dropouts to the chainstays at the same time you're brazing the chainstays into the shell? I am being sincere, not snarky.

    I can list reasons why I braze the steerer to crown, but the biggest reason in thats the way I've always done it. On my next fork,I will try doing the steerer/crown/blades at same time.
    I don't braze the drop outs into the chain stays when brazing them into the shell. For a few reasons- it makes cleaning up the drops more difficult and slower, and the stays are just floating then. As you know, brazing them first locks them into place while they're floating in the shell waiting to be tacked into a precise location.

    Do give it a try. The biggest reason that you gave is really what I was getting at. We all do things like that and in this era of frame builders learning by flickr and chat rooms lots of techniques get repeated by folks that are still trying to figure out how to light the torch. We all started somewhere and that's fine. I just think we can all do better than just regurgitating Paterak manual techniques. Especially when this is one's profession rather than hobby.
    Curt Goodrich
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  18. #18
    dbohemian is offline VSalonistas
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    Default Re: Fork questions

    Quote Originally Posted by Curt Goodrich View Post

    But if one has the equipment, why not save a little time, save some gas, and save the casting from another heat cycle? Seems like a win win situation and a no brainer to me.
    Have to agree with you here Curt. I build quite a bit of a frame as sub-assemblies but the fork I typically do up as one (crown/steerer/legs). It is one heat cycle vs two and I have no problem turning the whole race on my lathe or drilling it. My lug holders do a fine job with crowns and with some of the detail work I do from time to time it works better for me to be able to manipulate a crown without a steerer attached. I just got a new Anvil fork fixture and it's even slicker than the old one so seems like separating this step adds time without adding quality. I can see that there may be exceptions when one wants to add mounts and the like to the underneath side.
    All the best,

    David Bohm
    Bohemian Bicycles

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  19. #19
    edoz's Avatar
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    Default Re: Fork questions

    Quote Originally Posted by Curt Goodrich View Post
    As far as turning the crown race on a complete fork with the lathe it's a non-issue unless the lathe is quite small.
    When you spin a complete fork, you're also spinning an imbalanced part, as the rake sets the legs off center. Depending on your lathe, that could be an issue.
    Eric Doswell, aka Edoz
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  20. #20
    Alistair's Avatar
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    Default Re: Fork questions

    Quote Originally Posted by Curt Goodrich View Post
    Why are people brazing the steerer to the crown as a sub-assembly? I've never understood the rationale. Is there one? I'm not trying to stir the pot. I'm being sincere.

    Couple of thoughts on that one Curt.

    For myself, the spindle bore on my lathe is too small to accept a steerer. If I build a complete fork I have to use the steady rest to turn the race. It does work, but there is added set up time, and it's tricky to get things just right so that the steady rest arms aren't binding, but secure enough to get a chatter free cut. I've done it this way on a few forks. Enough to know that I don't like doing it. On a 300 and some pound lathe, the eccentric mass of the raked blades introduces vibrations and flex in the machine that make it tough to get a clean, accurate cut. In my experience anyway.

    Now I build a steerer/crown sub assy. which I turn between centers (0.010" oversize). Once the fork is finished and powdered/painted I do a finish cut with a crown race cutter, which gets the race to an accurately machined size, and removes any paint/powder.

    I think of this issue in a similar way to the different ways that people build frames. Some braze it all in one shot, some build a ST/BB sub assy., and some build the front triangle as a sub, then attach the rear end in a separate op. These (and other possibilities) different methods are used by pro's and newbs alike and done with enough care and skill result in quality frames, imho.

    I'm not saying that there's no wrong way, and some ways will make more sense than others from an engineering or metallurgical pov of course. Within the range of reasonable approaches though, I think it just comes down to what works for the builder w.r.t their construction philosophy, available tooling/machinery, work space, and the particular way they've decided to skin the cat, as it were.

    My 2 cents.

    Alistair.

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