Author Topic: Brazing Questions (Read 1479 times)

Sean · « **on:** April 22, 2011 - 12:39:15 AM »

Hey Everyone!
I've got a few pin sized holes in the channel around the front & read window and the firewall that I'm going to need to fix in the near future. I've been looking into brazing the holes shut. The car has been blasted and is in epoxy primer. My questions are:

1. Do I need an acetylene torch or can I use a propane torch for this kind of work. I don't have an acetylene torch but I do have a small propne bottle with torch tip commonly used for sweating in plumbing.

2. What kind of rods do I use? I've been looking around and would I be right to use R34 rods for sheetmetal?

3. I've also read that there is issues with primer/paint adhering to the brazed areas. To solve this, people (various other posts on the web) have suggested 'tinning' the metal to prepare it for primer/paint. What is used to tin the metal?

Thanks!!!

Sean

Super Blue 72 · « **Reply #1 on:** April 22, 2011 - 04:59:12 AM »

Sorry, I don't have any answers but am very curious, good questions.

72cudamaan · « **Reply #2 on:** April 22, 2011 - 09:32:24 AM »

Leading would be a better choice for that. Only requires a propane torch for the heat.
The area surrounding the leading must be very clean though.

Barracudadan · « **Reply #3 on:** April 22, 2011 - 10:50:45 AM »

Trying to remember what I was taught back in trade school about brazing. We used to use oxy/acetylene torches. Make a point with the flame to concentrate the heat at the tip. Any welding supply outfit even a Home Depot or Lowes will have braving rods and flux. I think a propane torch will work might need Mapp gas it burns hotter. Whereever you buy those small propane tanks they should have Mapp too. Definatly want to get to clean metal no matter what process you use. My advice be careful whats underneath whatever you braze/solder you don`t want to start a fire!

I found this searching the web:

Add Flux Or Use Protective Atmosphere
When brazing is done in the open air, the joints are normally pre-coated with flux, a chemical compound which protects the part surfaces from air. A flux coating helps prevent oxidation when the metal heats up, protects the braze alloy and improves its flow. As heat is applied to the joint, the flux will dissolve and absorb the oxides that form. A variety of fluxes are available for use at different temperatures, with different metals and for a variety of environmental conditions. The point to remember is that the flux should melt and become completely liquid before the alloy melts. Most often flux is sold in paste form so it can be brushed on to the parts just before the actual heating cycle.

Turn On The Heat!
Most brazing processes run at temperatures between 800�F and 2,000�F. For a strongest braze joint, the metals that are being joined together need to be at close to the same temperature. Slow heat cycles generally produce better results than fast heat cycles.

Basically yes flux the area you will braze,get it hot enough to flow.Brazing melts the filler rod not the base metal. When you braze warm the rod quickly and dip it in the flux so it sticks to the rod. I remember using a white powdery type of flux back in high school and brass rods. Then heat the area you want to braze when the base metal is hot enough apply the filler rod. Filler rod will travel towards the heat same as soldering. Practice on metal similar to what you need to repair first to get the feel for it.

Now with all that said leading is probably a better choice! Just wanted to tell you the basics on brazing class is dismissed time for recess go work on your car!

Topcat · « **Reply #4 on:** April 22, 2011 - 12:05:47 PM »

Quote from: 72cudamaan on April 22, 2011 - 09:32:24 AM

Leading would be a better choice for that. Only requires a propane torch for the heat.
The area surrounding the leading must be very clean though.

Heat weakens sheetmetal. Less heat is applied when doing lead.

Challenger III · « **Reply #5 on:** April 22, 2011 - 02:58:59 PM »

Sean, I would recommend using your mig to plug those holes. Too much heat with a torch. Use a piece of copper to back your weld (bar or paddle : http://www.streetrodderweb.com/tech/0909sr_1950_plymouth_three_window_coupe/photo_14.html ) the weld wont stick to it and it makes the repair look nice from the other side. Make sure you clean everything up good to prevent porous welds. You can keep your heat down by short bursts of your mig gun like shooting a squirt gun.

NC RMP · « **Reply #6 on:** April 22, 2011 - 04:25:04 PM »

My 2 cents......

Depends on your skills, your money, and what you're gonna do with the car.

I'd say if you have one and can use it the MIG welding them is best for sure.

If you don't havet the MIG another less costly option is to first clean the holess thoroughly, removing all the rust, then cover the hole inside and out with POR15 and then use Sonic weld or somthing to plug the holes. You can grind the sonic weld down so that it will never show.

72cudamaan · « **Reply #7 on:** April 22, 2011 - 09:21:01 PM »

Pin holes usually mean rust on the back side. Which usually means that the surrounding metal is thinner than the majority of the panel. Unless you are quite comfortable with mig welding, you could create more of a mess than you started with. Even wityh a copper paddle you could burn through easily. Leading uses a much lower temp. Or as mentioned, you might use a two part epoxy like J-B weld.

pywell · « **Reply #8 on:** April 23, 2011 - 12:00:24 AM »

There is a aluminum based body filler that may work to clean that up, its 100% waterproof too, there is also kitty hair fibreglass filler. All in all a repair any other way other then cutting out and welding in a new peice is very shady. Too many people do it and call it a repair until the poor guy find the paint bubbling a year after its painted. I would use the kitty hair filler, its strongish and waterproof then you put normal filler over, its your cheapest solution. Brazing... ugh brazing is for seams, brass is most common today. I would cut it out or do the copper backing and mig it in. I know your just looking for the easiest solution to keep it going, but its just going to get worse and doing anything else could actually cost you more afterwards to get it done right. Expecially since you have already got the car blasted... your nuts to take short cuts at this point.

Thats my 2 pennies.

Sean · « **Reply #9 on:** April 24, 2011 - 02:34:44 PM »

Thanks for all the responses guys!! I learned alot reading though the posts. Here's what I've decided to do - MIG them shut.

I was going to be taking the car over to my buddy's shop to do the fitment and welding of the rear sheetmetal on Monday (using his welder). Well, as life would have it, things have come up which will not allow me to dedicate my time at his shop. I don't want to impose in his shop with my schedule being hit or miss. I know he wouldn't mind, but I just don't want to 'take advantage' of his time and space - I'd feel worse about it than him. I found a Lincoln Pro MIG 180 on sale at Lowes for 20% off and am going to pick one up and get a few of the copper strips as well.

Again thanks for the feedback providing a newbie the knowledge to do it the right way!!!

Sean

pywell · « **Reply #10 on:** April 24, 2011 - 03:38:25 PM »

Quote from: Sean on April 24, 2011 - 02:34:44 PM

Thanks for all the responses guys!! I learned alot reading though the posts. Here's what I've decided to do - MIG them shut.

I was going to be taking the car over to my buddy's shop to do the fitment and welding of the rear sheetmetal on Monday (using his welder). Well, as life would have it, things have come up which will not allow me to dedicate my time at his shop. I don't want to impose in his shop with my schedule being hit or miss. I know he wouldn't mind, but I just don't want to 'take advantage' of his time and space - I'd feel worse about it than him. I found a Lincoln Pro MIG 180 on sale at Lowes for 20% off and am going to pick one up and get a few of the copper strips as well.

Again thanks for the feedback providing a newbie the knowledge to do it the right way!!!

Sean

Theres no chance your near me in Edmonton, Ab Canada hey? IL is a little bit of a trip, too bad. Good luck have you migged anything up before? Just make sure you control your heat, too hot and sheet metal warps. Grab some sheet metal scraps of the same thickness and practice/setup your welder to the right speed/heat level before doing it and you should have no problems. 2 Thumbs up for doing it the right way! You WONT regret it I promise!!

Sean · « **Reply #11 on:** April 24, 2011 - 06:32:06 PM »

Quote from: pywell on April 24, 2011 - 03:38:25 PM

Theres no chance your near me in Edmonton, Ab Canada hey? IL is a little bit of a trip, too bad. Good luck have you migged anything up before? Just make sure you control your heat, too hot and sheet metal warps. Grab some sheet metal scraps of the same thickness and practice/setup your welder to the right speed/heat level before doing it and you should have no problems. 2 Thumbs up for doing it the right way! You WONT regret it I promise!!

Not even close to any part of Canada! LOL! I have MIGed a little when I made my rotisserie at my buddy's house using his welder. He's offered to show me the ropes for sheetmetal and look over my shoulder until I get it down pat. It didn't take long for me to pick up on welding the 3/16 stock. I know that the technique is a little different for sheetmetal (no long beads, lower heat, etc...) and I'm ready for the challenge. Like you suggested, I'm going to practice on scrap until I get get a good rythem and feel going and then go live on the Cuda!

Sean

Jesus H Chrysler · « **Reply #12 on:** April 24, 2011 - 08:50:54 PM »

Having welded my share of rusty metal here's my 2 cents:

What you see as pin holes in the metal is really a much larger rusty area. The metal is gradually eaten away until it's thin enough to create the pin hole. If you try to fill up just the pin hole you'll end up trying to weld on metal that is much thinner than you expect. If you're like me you'll burn through very easily and create a bigger hole and a big mess trying to fix it.

You said the area has already been blasted. Take a metal pick or screwdriver and poke at the area. If you can poke the hole bigger or tear or dent the surrounding metal easily you may need to remove more before beginning your repair.

Topcat · « **Reply #13 on:** April 25, 2011 - 10:40:21 PM »

Quote from: Jesus H Chrysler on April 24, 2011 - 08:50:54 PM

Having welded my share of rusty metal here's my 2 cents:

What you see as pin holes in the metal is really a much larger rusty area. The metal is gradually eaten away until it's thin enough to create the pin hole. If you try to fill up just the pin hole you'll end up trying to weld on metal that is much thinner than you expect. If you're like me you'll burn through very easily and create a bigger hole and a big mess trying to fix it.

You said the area has already been blasted. Take a metal pick or screwdriver and poke at the area. If you can poke the hole bigger or tear or dent the surrounding metal easily you may need to remove more before beginning your repair.

Good point. Without a picture every situation warrants a different approach. Rust can be more than what you thought it was.

Sean · « **Reply #14 on:** April 25, 2011 - 11:52:22 PM »

Thanks for the tip JHC! You have to have something to weld to in order to weld, right!?! Will keep the advise close at hand.

Sean