first go at lead/bodysoldering

More of an art than a science - discuss metalworking and welding here.



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PostPosted: Sun Jun 10, 2012 12:08 pm
been dying to learn this for ages,

got the metal uber CLEAN. no paint, no dirt, no nothing on that,

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even went as far as to sand blast down the weld line to make sure it was 100% clean. then washed down with brake cleaner and left for an hour

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got the gas and torch

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on the clean and degrease metal you paint on a special tinning paste, its basically flus and powered lead, paint it everywhere.

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once its on you get the torch, started it on the red axy and then used a tiny bit of oxygen to get the flame completely blue, and with a very wide short flame (you dont need mega heat for this!)
heat the tinning until it starts smoking and turning brown (thats the flux) and you will see the lead melt shortly after , get a wet rag and very quickly wipe it, it will tin the entire surface with lead.

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if its not shiny you have got it to hot or done something wrong! (i stripped some of this off and redid it, mental note to not go for such a large area to start with)

now the lead bars i got off eaby were ****. there should be a wide temperature range on a 70 lead/30 tin lead bar but this stuff has such a narrow range between melting and going runny (you need it pasty)
half of this **** ran off the car and is on the floor. in the end broke into my bars i got for J16crx rebuild but never used and they were superb! very wide temperature range and very very easy to work with! (go frost on this one)

the process is pretty simple but hard to get right (as i found out)
you heat both the tinned panel and the end of a bar at the same time, as soon as the bar looks like its going soft you ram it onto the hot panel and twist it and a lup brakes off. you keep doing this until you think you have enough to fill the dent (i should have used alot more to start with).
if it gets to hot it turns liquid and runs off the panel, not enough and it wont spread

with the soft lead deposited you need to very quickly and very carefully heat the lead until it turns into butter, then using a maple padel dipped in tallow (stops the lead sticking to it) you push it down onto the lead and work it into place, this is alot harder than it sounds because you need to keep the lead soft enough with the torch to work, so its heat, paddle, heat, paddle. after 3 hours i got the hang of it lol! (gravity is not your friend here lol!, msot of mine ended up runnin down the panel and onto the floor)

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anyway the process is a bit like bodyfiller. do an area, until you think its right, then using a vixen file cut it down. low spots go back and again add lead , paddle and let it cool then file.
its a long process.

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file (came in the frost kit) is flexible, set it on the good side of the car and used that profile to sand the leaded side, added more lead and filed again etc etc (harder than it sounds because the base needs to melt to the new stuff and gravity pulls it down)

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anyway lots of flatting later (adding more lead when you see low spots that need more)

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should leave you something along these lines.

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i was naughty and cheated and used a 120 grit flappy pad in the angle grinder to remove some excess runs and slop here and there , used my 2k painting mask and used a hoover to suck up the dust off the floor and car


i think from now on im going to avoid using body filler in bodywork, lead costs 10x as much but its so much better than body-filler, it does not shrink and show through the paint 2 months down the line, it does not rust, its at least 10 times more flexible than filler if applied right, plus its a dying art and the satisfaction you get from using it is great :)
got plenty more to do so should be pretty good at this by the time i finish lol!

any tips are more than welcome :)



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PostPosted: Sun Jun 10, 2012 12:32 pm
aaran wrote:
got the gas and torch

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Are you using that cutting torch for lead work?



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PostPosted: Sun Jun 10, 2012 1:48 pm
yup.

seems to work fine, i can get a good short flame off the end (has a foot print around 1 inch) inch wide short blue flame off it which is what my soldering book suggests



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PostPosted: Sun Jun 10, 2012 8:29 pm
Its been said that using oxy/acc torch for leading is like using a boat oar to kill a fly, but many people did it for many years. Its just a lot of heat that you don't need (somewhere around 6800 degrees). I use a tip on the end of the torch that uses gas only (around 3500 degrees) http://www.eastwood.com/ew-body-solderi ... r-tip.html --or mapp and propane will also work well.

The blue metal in your pictures and the amount of lead you mentioned on the floor indicate that you are getting the metal too hot. That can lead to adhesion problems and poor workability, the tin and lead apparently do a little separation when melted.

Other suggestions that I could make are to work the surface more so you will not need so much filler, and apply enough lead the first time to do the job (which was a problem I had to solve also) When you come back and apply more, it all needs to be heated all the way to the metal, and that would be difficult for you to do. Also I don't recall any mention of neutralizing the flux acid, or removing the paddle wax, or use of a respirator.

I know this is not something that you want to hear, but if it was me I would remove all the lead and see what the metal looks like. It may teach you something that was done wrong (look for bare metal), and if everything is good, then consider it practice.

I wouldn't try using lead in the middle of a panel, it just causes too much distortion. After you file the lead, you will find that you always need more where you left off, due to shrinkage of the metal. Personally, I only use lead for its strength on panel edges. There is nothing wrong with modern fillers applied properly.

Good luck and enjoy.



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PostPosted: Mon Jun 11, 2012 2:23 am
thanks for the info on the torch, the torch will only run those sort of temperatures if you pull the trigger on the handle (it opens up the valves all the way and then it runs in "cutting" mode as it were) i just set the torch on an "idle" setting as it were and dont use it. from the videos i watched on youtube it seems to melt the lead bar around the same speed as a propane unit

from the amount i filed off the metal underneath looked good (it looked fine on the bottom of the panel as it was already the right shape i just melted the lead right off that part and it looked good underneath, no funny colors and still tinned lightly), that was the only place i got the metal blue because i forgot i had the torch it pointed at that point whiles paddling :knockout: (should have been paying more attention!). and yes i washed the work down with water and a rag after every layer went on and then reapplied flux on any bare metal after i filed it down before applying more lead.

not had any shrinkage yet, well not that i can tell as i dont file until after its been washed and fully cold. my paddle work does suck, might get some longer ones to help me spread it more even



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PostPosted: Mon Jun 11, 2012 6:51 am
The temperature I mentioned was the normal oxy gas welding temp. Mixing with oxygen doubles the temperture, so the push on tip that I mentioned only uses gas, but produces no soot.

The fuel gas commonly acetylene, when mixed with proper proportion of oxygen in a mixing chamber of welding torch, produces a very hot flame of about 5700-5800°F.
http://www.cedengineering.com/upload/Fu ... utting.pdf

The acid used for flux is very strong and cannot be neutralized with water alone. You need a base--such as baking soda mixed with water and scrubbed with a hand held stainless steel brush then rinsed with water. Distilled water will be less corrosive.

In working with the paddle, I prefer a short one. Its not good to spread the lead with the paddle, you will get trapped air and pin holes, just push it.

The shrinkage I mentioned wouldn't be so likely over a welded seam.



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PostPosted: Mon Jun 11, 2012 11:14 am
awesome thanks for the info. will re re clean the area with soda and my fine stainless wire brush tonight when i get down :)

i had my friend do a PPI test on one of these lead bars i got off ebay, it came back with this:

The sample you gave me comes out as - 98% Sn (Tin), 0.81% Cu (Copper) the remainder is trace elements. Gun reckons its "SN100C" but could be anything that has very similar composition. Hope thats of some use.


so im guessing its not lead that was designed for body soldering like 70/30 (lead/tin) (it was a nightmare to use and had a very very narrow working range, was either hard to sloppy as hell, unlike the bar i put on after which was sooo much more easy to get buttery)

i have another 6 bars on the way of the better frost stuff so might well just melt off all that lead and start from scratch, would having used that sort of content tin react with a 70/30 bar over the top? if i do decide to start over im guessing i will just have to melt that lead off (top to bottom) and then use a falppy pad to remove any trace until im back to shiny clean metal again correct?



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PostPosted: Mon Jun 11, 2012 12:20 pm
Sounds like a good plan, practice is always a good idea before starting something new. Use a respirator. I would try and get the metal worked a little better also, so you don't have to put so much lead on.



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PostPosted: Mon Jun 11, 2012 3:45 pm
i agree with that last part!

would have been easier to panel beat the weld line up and use less. i am a bugger when it comes to bodyfiller and filling things to not put enough in lol.

anyway used my last bar and started on the beated panel on the other side of the car (its been dented in the past and someone has used a spot weld puller to pull the panel back out and slapped loads of filler on it). my paddle work has improved loads, got it looking very smooth compared to the first time, also reasonably flat but again i pressed down to much in the center spreading the solder out and made a low spot when i came to file it whilst the edges were fine its jsut a few 1 inch spots in the center. i think to be safe at this stage im best to go over it all with a very light skim of body filler just to make sure i end up with no flat spots or high spots before the primer go;s on. i have 6 more bars on order which should be here soon so will get that other side redone and go from there.

on that note on lead when it comes to paint over it is it treated like bare metal? ie: use an etch primer first?



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PostPosted: Mon Jun 11, 2012 4:36 pm
When you are ready for paint you could use 80 DA scratch on the metal and then hand sand the lead with 180 then use the baking soda with water and SS wire brush again. You want to make sure there is no sand or other contaminates embedded in the lead. Then W&G remover and unreduced epoxy just like on the metal.

If you need to use body filler it could go over the epoxy and while sanding I would try not to break thru to the lead, because it will more difficult to clean at that point. You might even want to undercut the lead with your file just a little if you know filler will be added. Its my opinion that lead contamination is what causes most of the problems that people have when painting over it.
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