Fillet Practice

[mxboy349]

I decided to buy some tubing from Aircraft Spruce and do some practice joints. I have to say it’s more difficult than it looks on the old interwebs and I have a long way to go.

Tubing – 1-1/4 OD x 0.035 wall
Flux – Cycle Design LFB Flux
Brass – LFB Rod from Local Welding Supply

My observations.
Poor heat control.
Hard to “build” a fillet. (again poor heat control)
Little to no “internal fillet” – Should I be “tinning” the joint first?

Feel free to critique. More practice is planned. Here are some pics and you can see more over on my Flickr

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[Doug Fattic]

Eric, Here are 2 suggestions to make your practice easier. 1st buy some 1” tubing to attach to your 1 1/4” tubing. This is an easier joint to fillet braze when starting out because it doesn’t require as much heat control mastery to keep the proper amount of brass all around the fillet. When putting together 2 tubes of equal size, there is no place for the brass to flow into on the sides making an even brass width more challenging.

It is a principle of learning to start with easy projects as a foundation to work towards more difficult ones. Learning ability can be limited when one gets discouraged or frustrated. In fact you might want to start by just laying a bead of brass in a line on top of a tube concentrating on maintaining the same width and height of brass.

2nd you need to continuously move your joint so the brass will flow into its V. Each tube should be an equidistant angle from vertical so the brass won’t have a tendency to flow more onto one tube than the other. I suggest brazing one short stub onto one long tube (instead of 2 short lengths). The long length can become a handle to keep moving the joint in the right position.

It is not really possible to adequately critique brazing from a picture after it is done. It really should be done while doing it. For example a picture can show that the joint got too hot but not the reason. Was it because the flame was too big, too close, held in one place too long? Successful brazing is all about subtleties of time, distance, angle, etc. There is very little difference between success and a mess.

[Andrew R Stewart]

Comments- I would use one tube which is long enough to hold the work piece, during the brazing, so that you can quickly and safely turn the work about this and that way. Using gravity to work for you or to eliminate the effects of gravity along with positioning the travel of the fillet so that things go better is a good suggestion.

I would consider trying the GasFlux CO4 bronze filler. I find it easier to work with then the "generic" rods I have tried over the years. Henry James sells them, I find I like the 1/16" and 3/32" diameters. The smaller for flow and small fillet work and the thicker for the larger fillet work. As I get better I find myself reaching for the larger more and more.

I do a flow/tinning step then readjust the flame and go back to do the fillet work. I use to worry about getting a large internal fillet, now I just want to see some internal penetration. The sides of the miter where the cut tube wraps around the un mitered tube is where the internal fill is most focused (as the external fillet won't be as large).

During my practice I will start a rough filing step after doing the fillet. This is a feedback method to continually remind me of the goal of a smooth fillet with little need to spend extrat time working the files. Having a long enough tube to hold doubles in making this step far easier to do. I tend to prep/miter a batch of tube stubs but keep the uncut tube full length and do a practice brazing at it's end then do another a little bit further down and so on until the uncut tube has the batch all attached. At any point along this session I can cut off the earlier practice joints if I feel the need.

Have you also been measuring the before and the after joint angles? Andy.

[Ken Holmes]

First let me say that these look great for a first time with no one looking over your shoulder and pointing things out.

I really agree with what Andy and Doug are saying above.

I think it would also be useful if you described your torch setup, what your flame looks like when you set it, and generally how you are positioning and moving the torch and rod. The positioning and motion for me was the thing that was not obvious. FWIW Doug is totally right that is not really possible to give valid critique to brazing after the fact. That being said when I look at some of these fillets I see a torch that was sitting too long and pointing too directly at the joint. This puts a lot of heat into surrounding metal and the filler flows out to find it. The filler gets lumpy and hard to control, going everywhere.

Here is an exercise to try to get the idea of how to lay down heat with the torch. Forget making a joint. Instead on one of those practice tubes build up a mound of brass on its surface. Try and make it really high, like making a snowman out of filler on top of the tube. You will find you cant really build very high if your point your torch directly at the brass mound and hold it there as it will run all over the place. Getting in and out quick is the key, freezing and melting the brass. The cone in the torch flame (technical name?) may come within 1 mm or less to make that happen. I could say more but start with that and get the idea of melt-freeze-melt down and how to point your torch.

FYI I am also a huge fan of Gasflux rod. I think it flows better than the allstate and other random rod I have come into possession of.

[halekai]

Heat control in all of its forms. Gravity. Flame size and quality. I don't know if others do this but I have learned to keep the torch moving at all times...usually in line with what I am doing but also in and out. My flame is rarely ever still for more than 1/2 a second... especially when using silver.

I like the description above as freezing and melting the leading edge of the brass. Drawing it out at the leading edge. That is how I get full penetration. The best advice I ever got was from Eric Estlund..."Get a Smith A1A with some kevlar hoses" It changed my life!

One insight that I can offer is that flux has mass and density and flows as a liquid to the bottom of any potential space. you need to displace it (particularly when it forms a great gob) in order to get the brass to flow there instead. Usually this happens automatically but sometimes you need to reach in with the rod and wipe it out of the crevasse. Like in the BB, DT, ST junction where there is a little pool that is formed with no exit.

Regarding the turning of the piece. Try taking an old top tube or whatever you have around that is smaller than your practice tube and deform the end so that it slips into your practice tube in a friction fit. Then in your bike stand or vice and tube blocks, you can easily rotate the work so you can use gravity to work for you.

When I am pre-heating the work I start out with less flame than I need. Then adjust the flame up in half steps until I am right there where I can keep the heat input just right to move along at a reasonable speed. Remember to let the flame "look" at the piece with greater mass more than the one with lesser. Use torch angle, distance and movement to put the heat right where you want it.

The cool thing is that you are now in "the club" of people that have played with molten metal. It is beautiful and intoxicating. I dream about it often...the image of red hot steel and molten brass...wow! Now that you are in the club you have to promise not to tell anyone else!

[halekai]

Oops...name and such...

Hale Sramek
Halekai Machine

[Wolfman]

I'm in this learning stage as well and have a question. In various other threads it sounded like people were saying the HAZ, if the metal is pre-heated evenly / correctly, will extend around the entire tube you're joining to. First I want to be sure that is the correct understanding, and I'd like to know if that is that to avoid differential cooling and thus bending of the tube? It seems like I don't see that HAZ shape in most photos.

-Brice Harris

[halekai]

Yes. If you heat one area it will expand differentially.

[Eric Estlund]

A little cross post from my SO that seems relevant here. Just a visual of some preheat, brazing, etc in real time.

These are the fillets from the video link.