New to TIG... Some newbie questions

By welder_guy2001 (***)

Date 06-02-2003 03:37

your neighbors are an excellent resource. they can steer you in the right direction when it comes to learning how to weld, and what kind of welder to buy, and where to get a good deal. in fact, they'd probably love to show you how to do it, and even let you try it w/ their machines just to see if it's something you'd be interested in enough to buy your own machine. books are good for references and learning the theory behind welding, but when it comes down to it, WATCHING somebody weld is where you're gonna learn the most. and you learn a lot more by actually practicing. have fun!

By Niekie3 (***)

Date 06-02-2003 19:10

Hi EvelBMX

Just a thought: Most CrMo bicycle frames are brazed and not welded.

This does not mean that you can not weld it, only that you will then have to post weld heat treat which I believe would be a pain for somebody making a single frame.

Regards
Niekie Jooste
Fabristruct Solutions

By 49DegreesNorth (**)

Date 06-02-2003 19:13

Cheap TIG is a tough one. Plus although you won't need all that much power for bicycles you will need to have enough control and arc stability to make really pretty welds. Less expensive TIG machines are massive and DC (no aluminum). As you increase the price you get AC and the potential for portability.

I would advise you to find a shop somewhere -- perhaps your neighbors'? You might be surprised where you can find TIGs -- there is one available for public use in Seattle at an Art Academy, for example, for $45/yr. If you are near a big city you can find one.

Thing is, you won't need just the welder, you'll need an array of cutting, grinding, etc. tools. Work as an apprentice, student, whatever. Lie your butt off to get into the classes -- or talk to the teachers. Ideally, you could work in a bicycle shop which is already outfitted. You really don't want to reinvent the wleding of bicycles -- learn from someone who knows what they're doing.

All the nest,
Chris

P.S. If it is bicycles you want to build, some of the very finest are made by brazing. You could get yourself a OA torch relatively inexpensively.

By evelbmx (*)

Date 06-02-2003 22:11

Thanks for the info guys. I am going to stick with TIG, I have never seen a 20" bmx frame that has been brazed. Would either of these welders be good to learn with?

http://www.harborfreight.com/cpi/ctaf/displayanyitem.taf?Itemnumber=55195&auction=1

http://www.harborfreight.com/cpi/ctaf/displayanyitem.taf?Itemnumber=33245&auction=1

Thanks!

By welder_guy2001 (***)

Date 06-03-2003 01:27

also, some high end expensive bike frames are made out of titanium...a very difficult and unforgiving material to TIG weld not to mention expensive!

By Dirtrider (**)

Date 06-03-2003 18:10

Those are STICK/Arc welders....NOT tig.

By 49DegreesNorth (**)

Date 06-04-2003 00:50

People make BMX bikes w/TIG because it is relatively cheap and looks gnarly. A well-brazed frame would be stronger.

A TIG system will have a gas system (e.g. argon) associated with it. They are also expensive -- if you see an arc welder that costs like ten times what a stick welder does, it is probably a TIG.

By the way, do make sure to read the classified advertisements in your local paper -- I have been surprised by the stuff that pops up in Seattle.

Bikes are tricky -- often you want to weld odd alloys, titanium, and aluminum. You'll need a nice machine to do this, but don't despair -- be determined and you'll find a way!

Chris

By evelbmx (*)

Date 06-04-2003 07:03

I just want to do 4130 chromoloy, possible some true temper heat treated stuff...

I know some frames are brazed, but isnt that a commmon thing with lugged bike frames? Can you braze a lugless frame? My dad knows how to braze fairly well, he just doesnt know too much about TIG.

Also, say I wanted to learn brazing, could anyone show me what equipment I would need to start? Thanks!

By Dirtrider (**)

Date 06-04-2003 16:52

I believe all you'll need to braze is an Oxy/Acetylene torch kit...extremely cheap compared to TIG. You can get a little tote kit for like $265 with tanks & all. Brazing is deceivingly strong IF the joints are fit up properly.

By 49DegreesNorth (**)

Date 06-04-2003 19:07

Dirtrider is right, although I'd get bigger tanks or you'll go broke filling them.

You are right that most bicycle frames that are brazed use lugs. And you can purchase vy. cool, ornate lugs if you want to go this route.

Some of the very, very finest bicycles in the world, however, use a lugless construction method called fillet brazing. This requires skill, patience, an OA torch, and a fair amount of grinding Check out:

http://www.athertonbikes.com/bmx.htm

If you Google fillet brazing you'll find a lot more. Note that these bike frames cost thousands of dollars -- if you got good at this you could make some good money. Or a bike which would put your buddies' TIG welded bikes to shame!

Chris

By evelbmx (*)

Date 06-04-2003 21:53

Hmm I like this idea of fillet brazing. Are all those frames in the link brazed? I like this picture: http://www.athertonbikes.com/pictures/bmx/green4.jpg

Thats brazing correct? I like how the weld is pretty seamless, it looks really cool. Im off to the store today to check out some oxy/ace setups.

By 49DegreesNorth (**)

Date 06-05-2003 02:11

Yep, that is fillet brazed. All smooth and continuous like that. People who know bikes will STOP and gaze at your bike in awe and wonder if you do this right. It is by far the most high-end, over-the-top way to fabricate a bike. Be prepared to do a lot of grinding! And wear a respirator (really, really) when you're using flux. The stuff is nasty!

Chris

By billvanderhoof (****)

Date 06-05-2003 03:25

I am told that a lot of old tube frame airplanes had cr mo frames that were oxy acet welded. Should work for bikes also.
Bill

By Dirtrider (**)

Date 06-05-2003 19:17

Now look Evelbmx, there is only one rule here (well, actually I'm sure there are many rules, but just go with it), you must share your trials and tribulations with the board! You are not allowed to just take the info and disappear, we want to see what you build!! :)

I agree, that frame looks pretty cool. I do know that Cannondales frames looked exactly like that and they were TIG welded. One guy would tack up the frames, then another welder would tig weld once, then a second time using a more filler and going over the first weld and smoothing it over to get the same effect. I love the idea of brazing it though. It's just hard to get past the notion that it's not going to hold up to a big hit.

By evelbmx (*)

Date 06-05-2003 21:24

Oh I plan to show anything I have done! People here have been very friendly and thats a great thing. I have noticed other people posting pictures of their first couple welds and everyone seems to know how to help the person to make them nicer.

Does anyone know the tensile strength of a fillet brazed weld? I remember seeing it on a website but I lost it. And what about the tensile strength of a TIG weld? Dirtride you said its hard to get past the notion that it wont hold up to a big hit, well how big is a big hit?

By 49DegreesNorth (**)

Date 06-06-2003 20:18

Check out:
http://www.handyharmancanada.com/TheBrazingBook/Section%201/What%20brazing%20is%20all%20about/Part%201.htm

And:
http://www.gtgtandems.com/tech/brazing.html

I would bet that a fillet brazed joint would be WAY stronger than a TIG welded joint. At issue here is the heat affected zone of the base metal. OA welding would really screw up the kind of alloys you're working with -- you'd have to heat the metal near the weld so much that it would lose strength. TIG's HAZ is much smaller, but compare this to brazing, where essentially you're not getting hot enough to adversely affect the base metal. Plus that rounded appearance is not just for looks -- it is structurally stronger.

I'm no expert here -- this advice is worth all it cost! That second site seems to be in rough agreement with me, though... sounds like it's all in the craftsmanship of the joint.

Chris

By Dirtrider (**)

Date 06-06-2003 21:17

I guess what I meant was it's hard to get past the notion that something that looks "soldered" (i know it's a different process, but sort of similar) is going to be stronger than something that's melted together. But the reality is, it is stronger to braze.

I would like to see how the fit-up goes with the tubing prior to brazing. Is a typical fishmouth joint sufficient??

Great links there from 49degrees!

By Dirtrider (**)

Date 06-07-2003 17:30

Evelbmx,

Here are a few sites I found that sell frame building supplies, including lugs & things!

http://www.phred.org/~josh/build/suppliers.html

Still not sure though, do all brazed frames use lugs to connect the tubes or can you fishmouth the joint and build up the fillet braze around it????

Cool stuff though once you get to checking it out. I am an avid mountain biker and have been wanting to build a bike for my 5 year old that doesn't weight 30 lbs!! He's a really good ride, but he's not big enough yet for a 16" mtn bike, but too big for the junkie little bikes they sell at walmart.

By evelbmx (*)

Date 06-07-2003 20:16

I am pretty sure fillet brazing refers to not using lugs, and when using lugs its just considered brazing. When you ever build that bike for your son/daughter you should post it! That would be great to see.

By qaultra Date 08-19-2010 20:34

Hey Evil

Maybe you can get someone to assist you in you endeavers. Two heads are better that one and thats why we are knocking ourselves out to give you a hand. I agree...I want to see your work too! In the long run brazing is the cheaper route to go and the easiest. But none the less here is some interesting information for you bro'. I think you will find that the old addage does not apply here, because in this case cheaper may be better here. Again, I'm in agreement Dirtrider, I would really like to see your creation.

Fillet brazing vs. TIG welding
Brazing, a lower temperature process than welding, uses a bronze rod to create a fillet--a French word for ribbon--pronounced FILL-it (not fill-LAY). It was previously thought higher welding temperatures would ruin good tubing. We now know because welding is faster, the damaging effect of higher temperature is mitigated by shorter heat duration. While disagreements about the relative merits of lower temperature vs. shorter duration continue, a properly fillet-brazed joint will certainly have greater accident "survivability." I.E., if you run into a tree or parked car, a fillet-brazed joint is less likely to fail. Either joint will withstand decades of normal use.

Because the bronze fillet is softer than the steel tubing it joins, a skilled craftsman can sculpt a brazed joint without cutting into the tube. Please note that the quality of this sculpting (or craftsmanship) is highly variable--look for large smooth fillets with compound radii and long feathered edges. Beware of "overbite." Overbite, a result of hurried or sloppy work, is where part of the steel tube has been carelessly filed away at the edge of the fillet. This creates a stress riser that can lead to frame failure. Unfortunately, overbite is a common flaw found on many fillet-brazed frames.

Unavoidable downside of fillet brazing #1: Price. Because fillet brazed construction requires much more time and skill, the price of a properly fillet-brazed tandem frame will be $300-$500 higher. If the price differential is lower, inspect the joints carefully before taking delivery. Because of the price, most bicycle customers choose a TIG welded frame. Of the seven models of steel tandems we build here at Santana, only the Noventa is still fillet brazed.

Unavoidable downside of fillet brazing #2: Weight. A filleted joint, like a lugged joint, is slightly heavier than a TIG-welded joint (4oz penalty on a single bike, 12oz penalty on a tandem). However, because our fillet-brazed Noventa uses stronger and thinner Columbus NivaCrom tubing, it remains lighter than a TIG-welded cromoly frame. For an even lighter steel frame we could TIG-weld a Noventa, but since weight freaks (as opposed to workmanship freaks) prefer our lighter and less expensive aluminum Sovereign, we don't produce a TIG-welded Noventa.

Because a properly fillet-brazed frame is the ultimate hallmark of a skilled framebuilder, the best reason to buy a fillet-brazed frame is because you value the artistry and can appreciate the builder's skill

Other places to go to find out good information.

http://www.cannondale.com/usa/usaeng/ http://www.giant-bicycles.com/en-us/ http://www.mongoose.com/usa/usaeng/mtn/mtn