Gas Welding

[john pen]

I'm curious about the applications for oxy accet welding. Ive got an end table all cut and laid out but still don't have a mig yet. Ive got my stick welder but that seem to be a bit big for the job (not to mention a pain in the a@# ! ). I was curious if using my oa torch with the brazing(?) tip and rod would do the job. Ive done a bunch of exhaust repairs with it and other jobs and I'm thinking the welds will be pretty flat. Any thoughts or concerns on this method? Also what other applications would this type of welding be good for ?

[Franz]

If you're talking about O/A welding with steel, go for it, do some practicing first though. O/A steel is produces a damn good weld, if you know how to do it.
The process isn't a whole lot different from brazing, but it is different.
O/A was the process used to weld the first gas transmission pipelines, long before arc welding was available for field work.
Get the proper filler and do some practicing before you try it on the end table, and NO, you cannot use coat hangers.

[john pen]

Ok, so whats the differance between OA welding and brazing ? Im guessing the rod ? And what rod would you suggest ?

[joehobart]

welding is a fusion (usually with addition of filler) process. Brazing is basically using a low temp melt metal(silver, bronze) like glue.

For an end table, either process would yeild good strength. You said you already cut the parts... Brazing and butt/tee joints dont mix well. You really would need to design it to be lap joints to get it to really be strong with a brazing technique.

For welding, probably the easiest way to get some good filler is go buy a 2# spool of .030 ER70-s3 or s6 MIG wire, or go to the welding shop and get some RG45 or RG60 rods. You will want to do some serious practicing. O/A welding is almost as hard as TIG to get good results. Use your manual to lookup the correct tip for your torch.

Read up here:
http://www.esabna.com/EUWeb/OXY_handbook/589oxy13_1.htm

I recommend you practice running beads down the face of some 1" bar to learn how to manage the puddle. Once you get that groovin, do it again, but use filler. Then you can play with joints.

[john pen]

great site, Ill def. do some practicing before I tackle the table..thanks for the info

[Brainfarth]

I've never tried the university link before.. ESAB has it going on for online training. I think thats record time for me to put a link up on my site. ;) Thanks Joehobart.

[axehind]

Originally posted by joehobart

For welding, probably the easiest way to get some good filler is go buy a 2# spool of .030 ER70-s3 or s6 MIG wire, or go to the welding shop and get some RG45 or RG60 rods.

Am I reading this wrong? It sounds like your telling him to use .030 mig wire to O/A weld with. I know I'm new but it wont work (embarrassed to admit I tried it in the past). The RG45 or RG60 rods will though.

axehind

[david_r]

joehobart, fillet brazing offers excellent strength to a T or butt joint. Of course, it's not something to be learned overnight.

axehind,
What happened when you tried to use the mig wire?

[axehind]

Originally posted by david_r
axehind,
What happened when you tried to use the mig wire?


The wire kinda disappeared. It seemed like I couldnt even get it to the puddle. It would just melt and kind blow away. I dont think you could feed it fast enough for it to be of any use in O/A welding. Just my opinion.

axehind

[david_r]

Thanks for the info. If I ever have a roll of mig wire around, I'll have to duplicate your attempts.

[axehind]

No problem. I was using a #2 harris tip if I remember right. I got my torch setup in the mail late in the day and I didnt have any rod to try it that night with. So I thought I'd try the mig wire and thats what happened.
All in all I really like O/A welding. "T" joints are rather tough though.

axehind

[john pen]

hmmm...1 vote for brazing rod and 1 against...any other opinions ?

[INTP]

The Wall Mountain O/A video (http://www.weldingvideos.com/video1.html) is a good beginner's guide to O/A welding. It covers the basics very well, though it doesn't cover anything more advanced. Frankly, I wish they'd make an intermediate O/A video, and a TIG video. If you can't get one-on-one or classroom training, this video will help.

[MAC702]

Franz, what are the issues with using coat hanger wire? I've never done any O/A welding, but I know my dad used to use coat hanger wire when he had nothing else available and he keeps a bunch of it on hand still. Is it okay for certain jobs? Is it just too mild?

[david_r]

Originally posted by david_r
it's not something to be learned overnight.

I wasn't exactly voting for brazing, just pointing out that it isn't only a soldering type technique and is used for butt and T welds that do require signifigant strength.
Give it a shot on some scrap. That would be the best way to determine if you are up to the task and if the technique would offer the strength you are looking for. Design of the table would play a factor into the choice.
Google "fillet brazing" and you should get plenty of hits on bicycle frame building. They certainly take more abuse that most end tables.

[bomberz1qr20]

Originally posted by david_r
Google "fillet brazing" and you should get plenty of hits on bicycle frame building. They certainly take more abuse that most end tables.

Many high quality road and touring bikes are fillet brazed - not so common with mountain bikes though.

Fillet brazing is extremely strong, often stronger than welding in certain applications, such as bicycle frames. The lower temperatures don't adversely affect the metals being joined.

Very good site:

http://www.henryjames.com/

Ton of good info on fillet and lugged brazing for bikes. Definately one of my future projects after I'm out of welding class.

Fillet brazing is also very smooth and elegant looking. T-joints and lap joints are the strongest, butt joints (for reasons that escape me) are not recommended.

[bomberz1qr20]

Nice example of fillet brazing, and the bottom bracket of a road bike:

http://www.flying-scot.co.uk/frame_images/23447_bracket.jpg

[bomberz1qr20]

From another site, very nice fillet brazed headtube junction:

http://oswaldcycleworks.com/mwolhead.jpg

[Franz]

Mac the problem with coathangers is that they are scrap metal with little to no metalurgy behind them. The ones floating around today are a lot worse than the ones we used for emergency welding rod 40 years ago. The crap dip coating they put on them also screws up a lot of welds.
Try a couple welds on some scrap, one with a coathanger and one with welding rod, and you'll see the difference real quick.

ONE MORE TIME - the difference between welding and brazing~
Welding melts the parent metal and fuses it together when the weld pool cools, regardless of weather additional filler metal is added to the joynt or not.
Brazing does NOT melt the parent metal, the temperature is lower than that necessary to melt iron or steel, only the brazing metal is melted, and adheres to the parent metal.
BRAZING CAN BE DONE WITH METALS OTHER THAN BRASS such as aluminum, and silicon bronz and the technical definition of brazing relates more to the temperature the filler metal melts at. Brazing is more akin to soldering than it is to welding.
The only limiting factor in a brazed joynt, relative to strength, is joynt design and strength of filler metal.
When working with brass, or silver, there is a limitation to the distance the filler metal will bridge, so joynt design and fitup become very important. While brass can be piled almost to mountain heights, the bridging distance is only a few thousanths of an inch.

[MAC702]

From what I remember reading years ago, the difference in soldering and brazing:

Soldering is filler metals melting at less than 800 degrees F

Brazing is filler metals melting at greater than 800 degrees F

[Dman033189]

How much would it cost you to get into O/A welding?

[john pen]

When I went to the welding shop today for rod and a tip, they tried to sell me a new outfit..I think they said it was around $175 and included 1 welding/brazing tip, cutting torch , regulator and hoses...Not included were the bottles

[Dman033189]

ok thanks do you know how much the bottles are approx.

[john pen]

they can be bought or rented...prices vary with the size...

[joehobart]

Ahh yes, a single wire wouldnt work well at all. Heres how i do it with welding wire, based on some experimentation. I save my 'wasted' 8 feet of wire, when i have to change spools on the MIG. I wrap it around thumb and elbow for 2-4 wraps(i like 3 wraps for 1/8" steel), then grab one end and twist it enough to form a 'rod-like' object. I dont find much difference between this and 1/8" RG45 rod, but im no O/A master, im sure there is some subtle difference in melting rate due to higher surface area, but my skill level is not at a place where its something i notice. I use a #2 victor which is like a harris #4 on 1/8".


Fillet brazing is what i was taught to be called 'Bronze Welding' or Braze welding. Its the same basic idea as brazing, but you actually build up material, rather than capillary action of 'sucking' the bronze into the joint which is standard brazing. It certainly seems cool, but in my limited experiments, i found it to be more time consuming that just welding it, and more difficult to visually inspect for defects. Obviously it has its place. Check out that esab link, its got a whole chapter on it with some good tshooting pictures.

I recommend the wall mountain video as well, i own both the welding and cutting ones. This is a tough process to bootstrap yourself on. He has some great 'action shots' of puddle and filler work that will get you welding very quickly.

[axehind]

Originally posted by john pen
they can be bought or rented...prices vary with the size...

My harris setup was about $150. It came with a thin 12 foot hose so I bought a 1/4" 25 foot for about $35. Then I bought a cart from HF
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=43615
Good deal by the way for the price. Love it so far. Then I leased 2 tanks. One 150CF Acet and one 120CF Oxy for $15 each for the year. Plus to get them filled I think it was around $50-60 for that. Plus say $30 in welding tips and a spare cutting tip.

$150 - Harris torch set
$ 35 - 25 foot hose
$ 37 - HF Cart
$ 30 - tank lease
$ 30 - welding + cutting tips
$ 50 - tanks filled

$332 total.

You could save some money getting a used setup.

axehind

[john pen]

So, would Tig welding be the same as gas welding but with electricity replacing the flame ?

[Franz]

Originally posted by john pen
So, would Tig welding be the same as gas welding but with electricity replacing the flame ?

:cool: Very astute observation my western neighbor!
In a lot of ways, TIG is very similar to stick, and in a lot of ways, there is little comparison.
When I first started learning TIG, it was aparent that it was much like gas, and the techniques were almost identicle. TIG is sorta like gas with an accelorator peddle that allows you to totally control the heat.
In both processes, you develope a molten pool of the parent metal, and then add filler. One BIG advantage TIG has is you can put the pedal to the floor and heat up a small area a lot faster than you can with gas. The big advantage to this is you can have a smaller heat effected zone on the total weldment.

[LocostBuilder]

FYI: Quite a few British space framed race cars are mild steel braze welded together. From what I understand is the surrounding metal is not heat affected and if a tube is bent or damaged, they would just melt the joints out and replace with a new tube. The joints have to be very tight though.

LocostBuilder