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Building a Fork

Old 06-22-24, 05:55 PM
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Building a Fork

Andy sold me a few fork crowns here a little while back, and now I'm ready to get busy building me a fork for my road bike.

Existing fork is a Reynolds Ozuo Pro w/43mm offset. I think it's about 270 370mm, axle to crown (or something close).

Plan is to build a fork with as much tire clearance as possible. The Reynolds will clear 25's, but the rear end looks capable of at least 30's, so that is my goal...if not bigger.

I'm thinking something in the range of 42mm offset, and as long as possible. Slowing the steering is not a problem. Rim brakes, Dura-Ace 11 speed calipers. How wide a tire will fit between the brake shoes on these calipers?

I'll dry fit and check clearance, etc, before brazing the legs into the crown, but you guys are so dang smart, I'd like to solicit suggestions before I begin.

Please share any suggestions. Also, suggestions on a simple brazing fixture.


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Old 06-23-24, 12:08 AM
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Have only made TIG forks so don't have any suggestions about brazing. Yes double-check everything with a wheel in there while it's still tacked. 270mm can't be right. The (shop-bought) fork on my recent fixie build is 365mm and the carbon fork I have on my road-bike build is 367mm. The ones I've made have been more like 387mm. The radius of the rim is 311mm so 270mm wouldn't leave enough room for any tyre.

As for offset I have used the Reynolds 631 curved blades on two forks. They're really nice. But the offset on them seems a bit longer than stated. This gives you three options: (1) go with the offset they actually have; (2) have the blades actually start off going slightly backwards to make the offset what you want at the end (possible on a TIG fork, perhaps not if using a cast crown); (3) bend the actual blades a bit. Option 3 scares me but is definitely something you're supposed to be able to do.

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Old 06-23-24, 05:46 AM
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Corrected the length..., yes, 370mm.

I've got a wood fork blade bending thingie, made from the template that Hank, of Henry James, used to provide. It worked in the past. Hopefully I can find it in the garage.

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Old 06-23-24, 08:44 AM
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On road forks using standard reach brakes, like the Dura Ace ones you are using, I usually build around a 370 a-c. This will typically max out the reach on the brake pads allowing for the largest tire possible to fit under the caliper, of course the fork crown also needs to be wide enough. Under Dura Ace 9000 brakes i have squeezed a 32mm tire under them, a 30mm is plenty doable. I suggest brazing the steerer to the crown first so you can inspect and make sure you got full penetration of the filler from top to bottom around the circumference. Then you can cut the crown race to spec without have the entire fork to fight against. Next, I would fit up the blades, dropouts and crown together and tack the dropouts in place. Now with a solid steerer/crown and fork blades/dropouts you can better dry fit your brakes and wheel to get the most out of your brakes reach. In terms of fixturing, what are you currently using to build frames? Maybe you can use part of your existing jig depending on what it is. Do you have a flat table for checking alignment?
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Old 06-23-24, 08:57 AM
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Originally Posted by 8aaron8
On road forks using standard reach brakes, like the Dura Ace ones you are using, I usually build around a 370 a-c. This will typically max out the reach on the brake pads allowing for the largest tire possible to fit under the caliper, of course the fork crown also needs to be wide enough. Under Dura Ace 9000 brakes i have squeezed a 32mm tire under them, a 30mm is plenty doable. I suggest brazing the steerer to the crown first so you can inspect and make sure you got full penetration of the filler from top to bottom around the circumference. Then you can cut the crown race to spec without have the entire fork to fight against. Next, I would fit up the blades, dropouts and crown together and tack the dropouts in place. Now with a solid steerer/crown and fork blades/dropouts you can better dry fit your brakes and wheel to get the most out of your brakes reach. In terms of fixturing, what are you currently using to build frames? Maybe you can use part of your existing jig depending on what it is. Do you have a flat table for checking alignment?
I'll likely use brass for the steerer to crown attachment, then silver for the rest. Feeding the filler from the top, and pulling it out the bottom is the plan, that way I know there is full penetration.

I have a flat steel plate that I use to measure, and align, frames on. Also, a nice piece of flat aluminum plate. I'm thinking of using the later and building a fixture of some type on.
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Old 06-23-24, 11:31 AM
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I wouldn't use brass for the steerer. It's not going to move when you braze in the blades, if that's what you're worried about. The silver isn't going to melt a second time absent malpractice on your part. And you've built enough frames that I wouldn't expect that from you. Even if some of it does melt, it won't be enough that the fork crown moves. You could always drill the brake bolt hole and put a bolt in for unnecessary reassurance. If you aren't used to brazing something that heavy-duty with brass, it's possible it won't work out for you. I wouldn't want to try it, tbh. Brass takes a lot of heat, even if you're just brazing a lug.
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Old 06-23-24, 12:03 PM
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Originally Posted by guy153
Have only made TIG forks so don't have any suggestions about brazing. Yes double-check everything with a wheel in there while it's still tacked. 270mm can't be right. The (shop-bought) fork on my recent fixie build is 365mm and the carbon fork I have on my road-bike build is 367mm. The ones I've made have been more like 387mm. The radius of the rim is 311mm so 270mm wouldn't leave enough room for any tyre.

As for offset I have used the Reynolds 631 curved blades on two forks. They're really nice. But the offset on them seems a bit longer than stated. This gives you three options: (1) go with the offset they actually have; (2) have the blades actually start off going slightly backwards to make the offset what you want at the end (possible on a TIG fork, perhaps not if using a cast crown); (3) bend the actual blades a bit. Option 3 scares me but is definitely something you're supposed to be able to do.
There are a few other tricks to changing rake of factory bent blades. Rotate the dropout in the blade end so the axle is off center compared to the blade. Rocking/rotating the drop out one way increases the rake and reduces it if moved the other way. Cut the blade along the raked end for the dropout at a point that the remaining bend will produce the wanted rake (obviously to the point of having a long enough blade for the A-C). By placing the blade on a wood surface with the bend up. Tap the high point (rubber hammer) to bend down the amount of rake.

It was this issue, getting the rake your design calls for and also a blade into drop out "flow" that looks good that motivated me to make my first rake form. It's been many years since I bought pre raked blades. Andy


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Old 06-23-24, 12:06 PM
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Originally Posted by unterhausen
I wouldn't use brass for the steerer. It's not going to move when you braze in the blades, if that's what you're worried about. The silver isn't going to melt a second time absent malpractice on your part. And you've built enough frames that I wouldn't expect that from you. Even if some of it does melt, it won't be enough that the fork crown moves. You could always drill the brake bolt hole and put a bolt in for unnecessary reassurance. If you aren't used to brazing something that heavy-duty with brass, it's possible it won't work out for you. I wouldn't want to try it, tbh. Brass takes a lot of heat, even if you're just brazing a lug.
Some of us feel differently. I generally use brass/bronze for steerer to crowns for a few reasons. Andy
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Old 06-23-24, 07:03 PM
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I made over a thousand forks and they were almost all brazed in one go, steerer and blades in the same heating cycle. And all brass. I'm not declaring this the only way, but it's my preference.

Personally, I wouldn't ride a fork that was someone's first try, made without supervision from a seasoned pro. But I'm old and breakable, can't afford to fall down anymore. I don't know you; can I assume you have enough experience to know when a socket is fully brazed? You don't want to end up with this:




Modern crowns are often hollow or at least "hollowed" a bit in that area between the steerer and blade, but many are just solid steel there, making a place that's hard to get hot enough. The crown in the above pics is the solid kind. You have to soak in the heat long enough for it to conduct all the way to that cold spot, whatever crown you're using.

That's partly why I like to braze steerer and blades in one go. Once you have the crown hot enough to fully braze the steerer, you're pretty much there already, to having that cold spot at the back/bottom of the blade socket hot enough to flow the braze. Just braze blade #1 rapidly enough that when you go to blade #2, that side hasn't cooled down much.

I'm a fan of preforms — rings or other shapes of filler put inside the blade before assembly, so you draw the braze from the inside out. Then you're not holding a rod in your hand, or at least you don't have to, so you can hold a second torch in that hand. Preferably a rosebud.

I have brazed forks (steerer + blades) in two minutes, from sparking the flame to turning it off. I've watched famous name framebuilders take over 10 minutes, up to 15 minutes to do the same thing. That time-at-temperature isn't good for the strength of the steel in the HAZ. Two minutes isn't easy with only one torch, no matter how big. But if stuck with only one flame, make it a BIG one

I recommend oxy/propane, because you probably can't make as big a flame as you should be using with O/A, unless your acetylene cylinder is really large. You know about the maximum safe withdrawal rate for acetylene? We can discuss it further if not, but suffice it to say it's pretty low for hobbyist-sized bottles. No rosebuds allowed until you get into some pretty massive bottles. Propane has no such limit.

One more bit of advice, more for reducing cleanup of burnt flux and/or the surface pitting of the steel that can happen where the flux got burnt up.
Make your jig able to rotate in the plane that lets you do at least some of the heating with the steerer up, blades down. During this time, as the flux melts it flows down with gravity. Then when you flip it the other way for the main phase of brazing, you have this extra reservoir of molten flux that is now flowing back down the blades toward the braze. Those 2-minute brazed forks I made usually had zero burnt flux, so after a hot water soak to get the flux off, there was close to zero post-braze cleanup to do. That was on forks for fancy boutique bikes too, not skipping the cleanup due to low standards.

Here's my Alex Wetmore 80/20 hobbyist fork brazing jig, mounted to a Park stand with what I believe is the correct axis of rotation:


(sometimes sideways is handy too, like for flowing long tangs)

Flickr story here — more pics if interested, plus a gratuitous video that adds nothing but at least it's short.
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Old 06-24-24, 11:13 AM
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I've had two forks break on me. One was at the dropout between the blade end and the slot (just like Campy right rears do) the other was the steerer (but I didn't see the broken fork as I was only 10 years old and the shop did the replacement). Neither involved the crown, not that I haven't seen other failed crown joins... I have said for decades that the fork is likely the most important member of a frame, at least as far as safety is concerned. It's the only frame piece that is only connected at one end.

Yet I prefer brass/bronze for the joining of the steerer to crown even with its higher heat levels that are likely also applied for a longer time. I just feel that a poorly done silvered crown/steerer is worse than the same poorly done one in brass/bronze. Not that I do poor work Andy
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Old 06-24-24, 12:10 PM
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I always liked building forks. It's an easy project with a compact timeline. Then I saw someone say they started out making forks before making frames. Twelve, I think. I had a moment of panic when I saw that. I prefer people start out making racks. Rear racks, specifically.

I have wondered why people put broomsticks in their steerer. That's not something we do anymore. I doubt it was for joining reasons, and if it was, those bikes were surely joined with brass. I imagine there have been forks built with cast iron plumbing pipe over the years. Before the advent of consumer lawyers.
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Old 06-24-24, 06:11 PM
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My failing in terms of brazing, is I tend to add too much filler, and then I wind up with excess work cleaning off the excess on the lug edge.

And this won't be my first brazed fork, rather, I think, my fifth. It's been years, though, and I don't have a fixture.

One thing that had concerned me in the past, is that the fit of the blades into the crown tend to be pretty sloppy, with big gaps. Not ideal for silver. I'll have to get busy, though, and see how the parts I have now fit together. Hoping for a good fit...
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Old 06-24-24, 10:04 PM
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I'm sure you know to clean up inside the socket on IC crowns to get fresh shiny steel for the braze to bond with. The cast surface doesn't make nearly as strong a braze, not sure why.. But in doing so, you make the socket a bit bigger, the fit looser, so it's Catch 22. Unless you use brass.

I'm not adamant about any of that, we're always balancing competing requirements and there's no one correct way. I've silver brazed forks, but I used 40% silver — better at filling the gaps, which I felt were too large for 56%
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Old 06-25-24, 09:56 AM
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I think Andy and I have a similar posting philosophy that we expect more than just the OP to read what we say and someone sometime later will be searching for similar advice. So my comments are general and not necessarily directed towards Nessium. For context this summer is the beginning the of the 49th year I've taught framebuilding classes. I recommend for those at the start of the learning curve to braze their steerer to the crown with silver because it is a bit more forgiving to rookie mistakes than doing it with brass. Students have a hard time keeping their whole joint within the required temperature window and bad things happen when a thick steerer gets overheated or some parts not enough to flow brazing material everywhere.

Brazing together the crown and steerer 1st as a single step allows the builder to work on filing crown edges and perhaps deal with the brake hole before the blades might get in the way. This provides a solid foundation for assembly so the blades can be cut to the right length.

Common problem #1 is not moving the flame precisely enough to heat evenly all parts of the joint to be brazed. Developing the sense of how to move the flame most effectively takes practice. Very few people can do this when they are starting out. Typically some places get overheated and others don't get hot enough for sliver to flow there. Usually it is the entry area that gets cooked and the destination ignored too much. The steerer to crown is an easy braze. Their thickness slows the process down so a student has time to realize what is happening and adjust. I suggest they work in quarter section increments with the steerer pointing straight up with the silver flowing by gravity from the bottom of the crown down to the crown race. It is easy to tell when the silver peeks out beyond the crown race and they now can go to the next section. It is important that the steerer either stick through a little beyond the bottom of the crown or be recessed so the steerer doesn't quite reach the end of the socket. This is to assist in silver placement. The majority of students have a hard time keeping the silver at their preferred entry spot when it starts to melt. And it the meantime they have trouble with controlling the flame because their attention is on silver placement as it melts.

This brings us to common problem #2. Most students have a hard time moving their flame hand and the other braze holding hand independent of each other. If they are thinking about how to move their flame, the rod holding hand freezes (and ther end of the rod loses contact with the joint) or more likely when adding braze material their flame hand freezes and overheats wherever the flame is pointed. This inability to operate hands independently is why doing little tricks like having a stopping place for the end of the rod is essential for the inexperienced. 3 adjustments can assist with success. #1 if your silver is coiled, bend it straight as possible. Adjusting the silver position to account for the curve puts their brain on overload. In other words they aren't paying attention to their flame while operating their other hand. #2 keep the silver very near the joint when bringing the joint up to temperature. The time it takes to place the silver in position from your hand by your side (where it naturally rests) when the joint is up to temperature, most likely means bad things are happening with the flame on pause in your other hand. And #3, hold the rod at the angle so it doesn't slip away from where you want it to be placed as it melts. Knowing what are typical rookie mistakes and how to avoid them really shortens the learning curve.

That is enough for one post. More suggestions for later fork building procedures if anyone is interested.
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Old 06-25-24, 04:52 PM
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WRT brazing clearances and filler metal choice -the fork crowns (and lugs/bb's ) made by Allotec have, in my experience had way too much clearance for silver brazing. Sloppy as hell is another more accurate way to put it.

This is probably because they were intended for mass-produced factory use, where they've never even heard of Silver-brazing, let alone used it.

Regardless of clearances, you're going to complicate matters by trying to use too small of a torch tip for the size and mass involved with a fork crown (or BB for that matter).
Propane is your friend. You want a diffuse, soaking heat for that joint and one that doesn't take eons to get to the fillers liquidus. Longer heating = flux oxide saturation = a marginal or poorly brazed joint.
My fork brazing improved when I was using Acetylene by going up to a Victor #4 tip. Get a big flame and keep the tip a little farther back.
You need to make sure your Acetylene tank is 145 cubic feet or larger. 145 is even on the small size for the more common acetylene rosebuds.

You also gotta know that Propane is different beast than acetylene. Almost all the BTU's are in the outer cone with Propane. So trying to get things hotter by holding the inner cone closer is totally a losing proposition. It's the exact opposite with acetylene.
Almost all the heat is at the tip of the inner cone. I found it confusing when I first started to use Propane. I was stuck in the closer = hotter mindset. Now I know that when I want more heat I hold the propane tip farther back and stuff gets red mucho mas faster.

A longer tip is another thing that I think can help. It keeps your torch hand away from all that heat (don't underestimate this) and amplifies your hand movement so it's easier to get a larger area more evenly to temp..
The Victor FE tip I use is nearly 12" long and for big stuff I would never go back to a more common 5 or 6" UN-J tip.

Finally, breezes and drafts can really affect the process of getting the mass up to heat. If you're in a drafty shop it's helpful to build up a windbreak with firebricks or a metal plate(s).

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Old 06-25-24, 05:17 PM
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Originally Posted by unterhausen
I always liked building forks. It's an easy project with a compact timeline. Then I saw someone say they started out making forks before making frames. Twelve, I think. I had a moment of panic when I saw that. I prefer people start out making racks. Rear racks, specifically.

I have wondered why people put broomsticks in their steerer. That's not something we do anymore. I doubt it was for joining reasons, and if it was, those bikes were surely joined with brass. I imagine there have been forks built with cast iron plumbing pipe over the years. Before the advent of consumer lawyers.
There were bikes known to fail at the steerer/crown. Broomsticks were insurance, like seatbelts and helmets. (Europe in the 30s, 40s and 50s. Wannabe amateurs riding whatever somebody gave them.) Smart fellows who hammered in that broomstick got to ride the bike home after the steerer failed.
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Old 06-26-24, 08:24 PM
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The steerer fits perfectly in the crown. Good for either brass or silver. Forgot to check the blades in the crown. Soon...



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Old 06-26-24, 11:41 PM
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Check to see if the oval at the end is the same as the oval where you intend to cut it. It often isn't, I think probably due to stresses frozen in the metal from when the oval was formed. Hard to tell from a pic but it looks like maybe the case with these. Not a problem; it's easy to squish them a little this way or that to improve the fit.
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Old 06-29-24, 07:25 AM
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Brazing fork blades to a fork crown is one area I may have to help out a student more than other areas. For those not positive of their brazing skills, the easiest crowns to braze are the full sloping ones. The hardest are the ones that look like or have twin plates. This is because a beginner has a hard time keeping track of where his flame has been and where it should go to heat everything up evenly. They require more flame movement. Flat crowns are challenging to get silver at the inside (closest to the steerer) end of the fork blade. You can't tell visually if silver is there and flame access is limited. In this case I use a Meco or Paige rosebud (they don't have that big of a flame). Held further away from the joint, it can provide a more even soaking heat. in other words you can bring the whole unit up to temperature more slowly without overheating some place that might happen with a sharper flame.

As noted in previous posts, a fork crown to fork blade fit is often less than perfect. I have to squeeze the blades in a vise to make it ether more or less oval to fit a particular crown. Sometimes metal removal in the socket with a Dremel (or similar) is necessary. To help get clean shorelines I use a punch hit with a small hammer to smash the crown edges to fit more tightly against the blades. Those punch blows are usually very close together. This can also help tighte up the fit if it is a bit sloppy.

Cleaning up the inside of the crown in preparation for brazing can be done with a small steel dowel with a split on the end to wind up a bit of emery cloth. This dowel is held in the end of a drill. For a beginner with some imperfect but useble fixture I recommend brazing the blades to the crown before the dropouts to the blades. This way the extra flux on the inside of the blades can be washed out with hot water. And the blades aligned properly in preparation for brazing in the dropouts (which won't disturb alignment as much). Furthermore by brazing in one dropout at a time, a true wheel can be used to check that it centers between the 2 brazes. And if not a bit of metal removal can center the wheel before the other side is brazed.
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Old 06-30-24, 08:59 PM
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This probably should be a new topic thread, but since we're all jabbering away about forks, I wanted to ask about brazing sequence WRT fork tips.

I was taught many years ago that you braze the fork tips to the blades, and then separately you do the steerer to the crown. Then you do some / all of the finish work, and finally jig up everything and braze the blades into the crown.
But after everything cooled down, I was always running into needing to file one of the dropouts. After brazing an accurate wheel would never sit properly in the forks I used to do. I just assumed that is how things "worked".

Now recently I just started doing the crown / steerer / blades in one shot, and then I do the tips last. Whoa. The last two forks I did ended up pretty amazingly close compared to my old sequence. Small sample size, but . . .whoa.
I'm guessing that the expansion and contraction must not be even from one side to the next, and this throws things off some ?

Is this something other people have noticed ? That the post-brazing alignment is better with the tips done last ? I wish I tried it this way years ago, and I'm looking forward to trying this new (to me, at least) trick for the next forks I make.
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Old 07-01-24, 12:26 AM
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You're saying the fork blades are different lengths after you braze? I haven't noticed that, and I'm trying to imagine why it would happen. The problem that's fairly easy to get is the dropouts being too close together, especially if the crown features long tangs.

But distortion is a real issue with the way most fork fixtures work. Distortion is made worse if things are heated differentially. I try to heat the crown at both blades at the same time.

The post before yours suggests doing the dropouts last, so there are possibly lots of people out there doing it that way. Doug has had a lot of students
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Old 07-01-24, 07:40 AM
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When I was learning to build frames at Ellis-Briggs in Yorkshire in 1975, we brass brazed the blades and steerer to the crown all in one go (like Bulgie does) with one giant natural gas flame. Then we would align the blades on a very cool alignment jig and attach the dropouts not using any big fixture (it was a mechanism with an axle that attached to the end of the blades) after checking and adjusting their length with a true wheel.

In the States I've done it both ways (and have had students do it both ways) depending on the dropout to blades treatment. For example if using Henry James dropouts, I'd have students braze them into the blades 1st and file them up before brazing the blades to the crown. That unit is easier to file before it is attached to a crown. Years ago I had a massive fork fixture made by one fo my machinist friends that worked great for accuracy but unfortunately limited flame access so not great for students. I have a fixture that starts with the letter A for their use because of great access but almost every time requires some after brazing adjustment so the wheel centers. I have one in Bucha Ukraine too and the same problem exists.

What makes sense to me for those less experienced is to braze the blades to the crown first (after the crown is brazed to the steerer). This way distortion misalignment can be adjusted before the dropouts are brazed. In other words bend the blades so they are where they are supposed to be. The extra flux beginners should use can now be washed out of the inside of the blades. This is also the time that length can be perfected too. There is going to be less distortion brazing front dropouts (particularly the lugged kind Nessiem is going to use). I don't rely on my A fork fixture to give me 100% true results and something made out of 80/20 I would trust even less. The blades to crown done 1st and dropouts 2nd allows for more accurate length adjustment.
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Old 07-01-24, 08:24 AM
  #23  
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Doug, I'm having a bit of trouble understanding how you do dropouts last. Do you use the dropouts loose to fixture the blades?

Is "A" an Anvil?
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Old 07-01-24, 05:32 PM
  #24  
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I can stabilize the fork blades several ways depending on what fixture I am using. On my personal fixture I have cones that hold the ends of the blades at the right distance apart. On my/our commercially made fixture (no longer being made), I use plug dropouts to hold the blades in position. These plug dropouts are for positioning purposes only and will not be part of the built fork. I can also assist in holding the blades by using a C clamp squeezing 2 small pieces of wood between the blades stabilizing them more.
my personal fork fixture with cones to hold the blades the right distance apart while brazing the blades to the crown

Yuriy taking a picture of a just brazed brazed twin plate fork crown in Bucha, Ukraine in 2018. Yuriy had to hid out in a root cellar with his wife for 2 weeks while the Russians destroyed the town in 2022. They broke into this shop and stole lots of general things but not our specific bike tools.


you can see in this picture that Henry James dropouts are spacing the blades while the crown plates are being brazed together. The picture shows what was the peaceful back of the college campus
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Old 07-01-24, 07:28 PM
  #25  
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The way we did 'em at Davidson (mid-'80s thru '90s) seems to me to be the best, especially for efficiency — we made them so quickly that they were cheaper to us than buying pre-made forks from Tange. We even sold finished forks to a couple other companies. Probably after our markup they were a bit more $ than Tange forks, but those wholesale customers were selling high-end bikes where the higher quality of one from 'big D' was worth the small price premium. But I just made 'em, I wasn't privy to the business details. One company, after buying a hundred forks from us, switched to having them made in Taiwan with knock-off crowns identical to ours except for that company's logo cast-in, by Long Shen or Everest or who knows. Ours were precision cast in Japan by Hitachi, noticeably finer if you have the eye. The Taiwan forks were a little less visually perfect but I'm sure they were much cheaper and most customers will never notice. And the cast-in logo is a flex.

I hope Bill won't mind me describing his method, since he's retiring and probably hasn't made a fork in some while.
  • Braze crown to steerer and straight blades in one go, on a 4-fork carousel. Two oxy-propane rosebuds at a pre-warming station before it gets to the human brazer, then a big hand-held torch to finish. They heat the crown rapidly, but while also soaking the heat to the deepest areas. Brass preforms inside the blades, so they're brazed from the inside out. Close to zero post-braze cleanup needed, pretty much ever. The whole heating cycle took about 2 minutes. That's one minute at the pre-warming station, and one with the human brazer. Station #1 is a second person (apprentice) fluxing and loading, unloading finished forks after they cool at station #4, and locking/unlocking/rotating the carousel. Pneumatic cylinders to lock/unlock, and move the rosebuds out of the way when unlocked, to clear the fork, then back in on the next fork as it locks, all from one foot-pedal. (Bill singlehandedly designed and built the carousel, and it was flawless! Rotated on a Volvo wheel bearing from a junk yard.) We often completed a batch of 50 forks in under an hour, around a minute each, but with two people working that's two man-minutes each. One of whom could be a low-skilled worker. Keeping up that pace would be hellish if you had to do it all day, but it was more like once every-other week, and it was actually kinda fun. Me and the apprentice sort of racing each other, because if you got ahead, you got a little rest (maybe 5-sec.) between forks.
  • Do a preliminary alignment check so they're equally spaced right to left and front to back. Often no change needed, so maybe a 1-minute job on average, counting the ones that did and didn't need any adjustment. If a blade needs to be moved, that's done with a heavy soft-rubber mallet, which takes around one second. Check - whap - check - maybe another whap and check, done. With practice you know exactly how hard to swing the mallet for a given amount of movement needed, so the first whap is usually all it needs.
  • Curve both blades at once, obviously on a fixture with two curved forms. These float horizontally to align themselves with the blade splay angle, which varies depending on how wide the crown is. 30-second job
  • Cut the small end to length on a fixture that indexes off the brake hole, so the tips are equidistant from the brake hole. Well, two fixtures really, the first one with an abrasive cutoff saw that removes the little (2 cm?) straight section from raking, and gets 'em close to the final length (30 seconds). The other fixture on the lathe, to make them perfect (another 30 seconds). The lathe cutter reams and faces the small end at once, exactly like a tiny headtube reamer/facer tool. Both these fixtures just have a 6 mm pin that goes through the brake hole, and the fork is dropped on and held lightly by the worker's free hand, zero time spent locking it down because it doesn't need it.
  • Braze the tips, which were a cast part that plugged into the ID of the blade, and had a shoulder that mated up with the faced end. The blades being lightly reamed, fit the OD of the plug with a just-right brazing clearance and were guaranteed to have clean shiny steel for braze to bind to. The dropouts had their cylindrical plug surface lightly cleaned (cast surface barely removed) by an apprentice who could do a hundred in a sitting, probably 30 seconds per pair. Brazed with pre-placed springs of brass (purchased already wound up, from Silva), super clean and almost no post-braze cleanup. About 1 minute total to braze both sides, maybe 2 minutes for cosmetic cleanup after the flux soak.
  • Final alignment. Wheel sits straight close to 100% of the time, and we were picky about alignment. Never filed a dropout, which is a substandard way to align a fork IMHO. The proper procedure takes longer the write up, and I probably have, check the archives? Basically you increase the curve on the longer blade, or decrease it on the shorter, then compensate up at the crown so the tips are back to the same place fore-aft. But regardless of how the fork was made, you should never file the dropout. It's visible evidence that you failed.
But what if you don't want those IC dropouts — you want to use classic slotted type? The fixture to hold the fork to the lathe, for facing the small end, could also be mounted at a right angle to the lathe bed, where a slitting saw of the correct width could make a slot for slotted dropouts. Run that up to a hard stop on the cross slide, so the slots are exactly the same distance from the brake hole.

Now, regular forged dropouts like Campy have a somewhat imprecise rounded shoulder, which could be a source of misalignment. Many FBs file that rounded shoulder to a sharp 90 one, but the filing isn't precisely repeatable, so each DO can be a little different length from shoulder to axle. We made that repeatble by machining the rounded shoulder to a sharp one, again on the lathe, so they were exactly the same length from the axle. Took a few minutes, but worth it to have forks come out straight, first try ever time. The arbor to hold dropouts on the lathe for repeatable shoulder-squaring is a bit hard to describe but if you just looked at it you'd grok the concept instantly. It was just a slug of round bar that you'd chuck in the 3-jaw, with a bit more than half milled off at the end, so it's a D-section. Then there's a tapped hole for a shoulder bolt that secures the dropout, shoulder at nominal 9 mm that fits the DO just as an axle would. The D-section is milled at a slight angle to the lathe axis so the part you're turning is on the axis, correcting for how dropouts are slightly bent for R & L.

All those special tools and fixtures cost money, so this method doesn't lend itself to one guy making one fork. It sure paid off over the thousands of forks we made though. Maybe there's some take-aways there for the one-man shop making one fork, dunno.

OK I ended up writing a dang book again, I must enjoy remembering those times. Apologies if it's tl;dr

Last edited by bulgie; 07-01-24 at 07:55 PM.
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