Brazing Practice- Sort of!
 

Thanks to a fellow here on BF I was able to get some old crowns,steerer tube and bits of fork blades to to do some practice.
My idea was to use brass for the steerer to crown. But after a few attempts I have come to the conclusion that oxy/propane just doesn't produce enough heat. Using silver worked fine.
So next up I would like to fuss with using brass to braze a lug. My idea is to use 2 different size tubes to simulate lug & tube. But is it the same technique to draw the brass through?
Any thoughts/advice would be great!
Now that I am caught up on house projects and am just at the bike shop 2-3 days per week I have so e time to play Framebuilder!

What's your torch setup? Oxy/Propane is not only adequate to the job, it is much preferred over O/A for brass brazing crowns or any other large joint where you want everything hot at once. I include lugs in that category, but there are many fine builders who braze lugs slowly, only flowing a fraction of the lug at a time. Even for that slow lug brazing method though, I'd still prefer propane

O/A is severely limited in how big a flame you can get, unless you use a bigger acetylene bottle than almost any hobbyist would use. The max witdrawal rate is a proportion of the bottle size, so small bottles can only make small flames. Unless you make a manifold with a number of bottles all flowing at the same time, which used to be done in industry, not sure if anyone does that anymore.

When I "graduated" from acetylene to propane for fork brazing, it vastly reduced the time it took, just because of how much more heat there was in the propane flame. Never could have gotten that big a flame with any of the O/A setups I had used previously.

I can see why a hobbyist might want to braze the steerer-cown separately, and the blades-crown later, but that's hugely inefficient. Once that big chunk of crown is at brazing temp for the steerer, you should braze the blades right then and there, sez I.

I'm using Paige tips. My last attempt was using the Rosebud. I did the preheat then concentrated on one area. But the brass would not flow through the crown. I cut it apart afterwards to see how far it went. Maybe more practice? But I need to obtain more crowns!

Yes oxy/propane is perfectly adequate to braze heavy parts. You would need at least a size 5 or 6 (Victor). I couldn't find a chart for Paige tips to compare.

What's your oxygen source?

I should contribute to this thread as I'm that "fellow" Tom sourced from. Glad to see his playing with the bits I sent. I pretty much said the same WRT propane's being able to produce the heat but suggested the issue is the small torch set up.

When I braze a crown/steerer (these days nearly only with bronze) with my O/A set up I use a tip with about .060" diameter. I find that tip size (for my Victor J28 this means a #3 tip, for my Purox it's a #15) is about the max I can run with the mid/smaller A tanks I use. I haven't gotten Acetone spitting out... But this made me remember some forum I attended back in 2019 we had much the same discussion about A flow volume WRT tank size (or the surface area of the top of the dissolved A inside the tank). Here's a chart referencing this flow volume VS tank size from, I believe, Smith. Andy.

https://cimg7.ibsrv.net/gimg/bikefor...403654ec7e.jpg

My 02 source is a concentrator. I will do some research to see how my Paige tips size relates to OA tips.

Small O2 concentrators have a limited capacity. In my experience you need 2 Lpm for a #2 tip, 4 Lpm for a #4, etc... So yours might not have enough flow for a big tip.

You can make a half box with 3 firebricks; it can make a difference for heavy fork crowns and a limited heat output.

I was running my concentrator @ 5lpm the Rosebud.

The brazing tip I use for doing fork crown brazing to either a steerer or blades is a G-Tec 3-TEN tip. Don't confuse this tip with any other brand including Genetic and their TEN tips. These TEN tips have no relation in size to the Victor TEN tips for propane. This G-tec multi-port tip is WAY bigger than any Paige tip. The center orifice is .062" (about the size of a Victor #3) and the six side orifices surrounding the center hole are around .030" + (meaning a little bigger than 30 thousandths of an inch each). In other words each side hole is as big as a Victor #0 tip. And there are 6 of them. The center flame is nice and sharp while the side flames stabilize the flame to keep it from blowing out with gas pressure blow back. I prefer this tip much more than a rose bud for fork brazing because of the sharp flame point coming out of the center hole that is great for cleaning shorelines. I run this tip with my Devilbiss 5 lpm model 515 oxygen concentrator. Works great. A Devilbiss concentrator puts out more oxygen than other brands.

The G-tec company: <https://www.gas-tec.com/torchtips> also makes their single orifice TEN tips (NOT to be confused with the sizing on their TEN multi-port tips) out of brass instead of copper. These are Victor TEN single orifice clones for propane brazing too. They are the cheapest place I know to buy Victor style TEN tips. They were out of some sizes between 0 and 5.

Tom, I applaud your willingness to experiment with how to make a fork. I must say that the one place I would not try and use brass is brazing the steerer to the crown. It is so much easier to use silver and it doesn't take that much. If you are in a production setting and brazing forks the way budgie does, then cranking up the heat and doing the steerer and crown all in one go with brass makes the most sense. I'll explain in another post why it is easier for amateurs to separate that procedure. For starters it reduces the skill level needed and is more likely to get better results. The skill level Mark has is huge compared to most amateurs.

Doug,Thanks for weighing in! After a few dismal attempts at using brass I pulled out the manual from class and proceeded to do one with silver. Bingo!
Today's time in the shop I am going to scrounge up some tubing and do a few slip joints with brass and see if I can flow it through.

Had the opportunity to spend some time with the torch today. Took all the torch tips and boiled them to give them a good cleaning.
So I attempted to brass braze a slip tube joint, one over the other. The larger was about 1" long.And I still struggled to flow the brass all the way through around the whole tube. I beginning to wonder if I need more clearance?
On a good note every steerer tube to crown that I silver brazed flowed through!
Since I am back at the bike shop for the next few days there will be no torch time until next week.

I'll defer to Doug's recommendations for beginners and hobbyists. I agree that my own time as a beginner was too long ago, so I don't remember what it was like. Versus Doug's interacting with them all the time. The last time I taught beginners was 35 years ago.

I didn't think of myself as that skilled when I brazed my first fork — with brass, came out great and is still being ridden 50 years later. But I had been working at a framebuilding shop for at least a year by then, and had two journeyman FBs looking over my shoulder and sometimes holding my hand literally. So by the time I made my first fork (for my roommate!) I wasn't really a beginner anymore. Nobody in the US gets to be an apprentice for a year before making their first fork these days, that world is gone. (Except for Taiwan and China maybe?)

I am trying to remember why I thought forks should be brass brazed! Almost all of the 1000+ forks I made were brass brazed, but why? Other than maybe some blades that are a bad fit with the sockets, most forks are probably fine with silver. And if that's easier (it's not, for me), then sure, go ahead and silver braze. The cost for one fork's worth of silver isn't going to break the budget.

The next fork I make will probably be brass brazed, but I have the luxury of two torches and a Gasaver. As many here know, a Gasaver is a device that turns off the flow of fuel and O2 when you hang up the torch. So I can use both torches for the heating phase, and hang up the second torch when the crown gets up to brazing temperature, to free up one hand to hold the filler. If anyone is thinking of setting up like that, I can give some tips, but I'm guessing that will not be popular with hobbyists. For example I use two O2 concetrators to do it, one 5 L/min unit wouldn't make enough O2 to run two very large flames. Two torches can run off one O2 bottle and regulator though, with a Y-splitter, for those still using bottled O2. And one bottle takes up a lot less floor space than two O2 concentrators.

Note if you buy a Gasaver used (as I did, mine used to be Mario Confente's), it'll probably come with the pilot light made for acetylene, but the part to convert it to propane is available and cheap. As with torch tips, you can sorta use the acetylene one, but the pilot flame is harder to light, and blows out easily. The pilot light isn't strictly necessary, but it's very nice to be able to pick up the torch and have it light instantly, with the valves still set to the flame you had adjusted it to when you hung it up.

Once you have two torches, you'll find other uses for them, like repairs where you have to sweat a tube out of a lug — it needs to be above the liquidus of the brass everywhere at once, difficult with one torch. Or heavy non-bike heating tasks, like the cracked cast-iron vise I brazed. Brazing CI requires a long slow pre-heat followed by slow cooling, to prevent cracking, but it can be stronger than welding. And very few people skilled at CI welding are around anymore, the last guy we had around here ("Cast Iron Mike"), who could weld a cracked engine block or exhaust manifold to good as new, passed away a couple years ago. Now that's a hard skill to master!

If you're using the usual 0.058" wall stuff for slip joints that's a good clearance for brass. Looks like you need more heat (or better technique?)

Next week I will give it another go!
But a question about "more heat". I have an old frame I want to deconstruct and since I am not sure my oxy/propane will be enough I had an idea to run by you fellows. The idea of 2 torches has been broached. I don't have 2 oxy/propane ones but what about using just a propane torch as a 2nd?

Oxy-propane is fully capable of brazing fork crowns. While the oxy-propane flame is slightly cooler than an oxy-acetylene flame, it is plenty hot to melt brass and, in fact, delivers higher heat (as opposed to temperature) than oxy-acetylene, due to the larger propane molecule being burned. We used oxy-propane at Trek; I used a big "rosebud" tip to quickly heat massive parts like fork crowns and bottom bracket shells. At home now, I use oxy-acetylene, but my tanks can't deliver the gas volume needed to sustain a flame with the rosebud tip.:cry:
https://cimg8.ibsrv.net/gimg/bikefor...dd61183a87.jpg
https://cimg0.ibsrv.net/gimg/bikefor...d50ddbcc79.jpg

Back in the early days of interweb and forums/email lists an early Trek builder was a contributor, sorry but his name escapes me. He described some of the brazing methods they played with to speed up the process. Two torches was done both by two people and just one. The two people efforts did take a bit of coordination between them and but for needing that second set of hands and eyes (added labor cost per frame offset the faster work) they might have continued it. Now I was more interested in the one person and two torches and their mouth held the filler rod (where was OSHA:)). The mental image was nearly funny.

I've tried two torches myself but I made a torch stand (along the lines of a microphone stand) and that second flame really needs to be moving about if you're using a normal tip (and it's very concentrated flame), perhaps a rosebud flame might not produce a too hot spot too soon. I've also tried this with a simple propane /air torch (hardware store cylinder) when removing dropouts and for this the stationary flame works better but is hard to keep aiming where you want it as you play with the hot dropout/stay unit.

By all means do play with a second flame, safely please though. I found myself forgetting about that second flame at times and could have bumped it or burned myself if I wasn't careful. How you set up the torches and joint to be pulled apart is important, I'll add a weight (hanging from a wire or vise grips clamped onto the part that will fall down after the filler is completely liquefied. Andy.

Was that John Thompson? I think he is still here. There is a fun video on YouTube of Will, one of Davidson's builders, dancing with 2 big torches. My guess is Bulgie has some great stories about that!

Tuz mentioned .058" tubing and one thought I had was that if the gap isn't big enough, getting brass to flow into the joint is pretty tough. Silver likes a small gap but brass likes a little more room. Most crowns I have come across have pretty tight fit on the steerer so you'd need to grind out a little to get brass to flow well..

"Was that John Thompson?" Duanedr

No, not John. IIRC it was Joe Stark. I wonder what has become of him. To continue this tangent (hope that's ok) Gene Powell is another person from way back when, he painted a couple of frames for me, that I get confused with Joe... Old mind and I've always been a poor name rememberer all my life.

I usually use a Dremel or a 1/4" die grinder to do the tube ID clean up and or clearance creation work. A tad noisy and a bit "dirty" but works well enough. When I attended the 1979 Eisentraut course we used reamers to open up the sockets. Quicker and no power tools for the students to hurt themselves with:) Andy

Just realized John posted above in this thread...clearly 'following along' is not my forte. I use an air powered die grinder. Even noisier and dirtier...:(

Tom, I'm going to restate the obvious but when builders say "more heat" we are talking about volume. The torch tip has to have big enough holes to put out a decent sized flame. The Paige tips were designed for the jeweler trade brazing small items. The G-tec company makes tips for the general industry that requires more BTUs. So if you are going to start the process of brass brazing forks you need the right equipment to do it properly. The multi-port G-tec TEN #3 is a good place to start. An alternative is a Victor #4 TEN tip - which is a single orifice recessed tip. Victor tips are really expensive so the G-tec is probably less expensive than the Victor. Yes a Victor or clone #3 TEN tip will braze your sleeves. The smaller the tip size the more pressure on the brazer to have a better more precise pattern. One of the most common beginner mistakes is to not move their flame evenly over their work. A similar example would be like painting a wall and putting too many coats some places and not enough other places and still getting paint on the ceiling and floor. A bigger tip held further away works better for the learner. This kind of soaking heat put less pressure on brazing with a precise flame pattern.

Doug,
I started looking at the Gas-tech site. So multi or single flame tips? I looks like a mixer is required between the torch body and the gooseneck.
All there text talks about NG so I assume they are compatible with propane.