Ok here goes. Idiots guide time. Its been a long time since i had my hands on a set of bottles.
Q1 - is it acetelene on first, off last. get a flame that doesnt produce too much soot then feed the oxy in till i get a good tip????

Q2 - I only have the bottles - what do i need to buy in the way of brazing rods and flux?
Im going to be brazing over my sump welds to seal them and also need to braze the strainer back onto oil pick up pipe.

Q3 - How do i do the actual brazing?

I hope this isnt too basic for you guys. Treat me as a total newbie on this one and dont assume prior knowledge!!!

Same old message. Get proffesional advise. This is not a subject you will learn about properly in a few posts from, possibly il-informed, members. If you had learned to weld properly in the first place you would not be needing to seal your welds.
Bruce.

That advice was a bit sharp, Bruce!

Welding the very thin metal on a sump is very difficult - I had to braze over my first attempt (the 2nd attempt was done in a totally different way, and the welding was easier). If I was doing it again I'd braze it from the start.

Brazing non-critical/non-structural work is not too hard to learn, provided you're prepared to practice a bit on scrap before you try anything important.

First step (and most important) is to get the work as clean and grease-free as you can manage. Wire-brush any welding oxide off, and de-grease as much as you possibly can. This improves your chances of success 100%. Also de-grease your brazing rods, if they're not flux-coated.

Get some good-quality brazing rods from a good supplier - ask for advice on the best grade (my local BOC shop is always good at helping). Flux-coated rods are easiest, but otherwise you'll need a tin of flux powder.

Then it's a case of heating the work to bright orange (no hotter - you're not welding!) and applying the brazing rod (direct if it's fluxed, otherwise warm it a bit and dip it into the flux powder). Move the flame along the work, following with the rod touching now and again to top up the braze puddle. If everything is OK you'll see the puddle following the flame.

The one thing you've have to get right is the setting of the oxy-acet flame - I always set it to 'neutral' but I'm not sure if that's correct - it worked for me anyway. A bit of advice on flame settings and nozzle size from an expert is always useful, and hard to pick up from a book. There's also the safety aspect, e.g. avoiding blow-backs, and what to do if you get one!

Hope this helps for a start...

David

I know its acetelene one first then oxy to get the right flame. Thats all I can help with I'm afraid.

I agree with Bruce. Get some proper training, or get someone who knows what they are doing to show you what to do. Oxyacetlene bottles are very dangerous things to have around even on their own, before you even start setting fire to their contents!

David

If axy-acetylene worries you, try oxy-propane - far safer. It will do everything that acetylene will do, apart from fusion welding. Much cheaper, too!

Otherwise, a propane/compressed air burner is excellent, although the flame is broader and tends to heat the whole thing, rather than a localised patch.

(what scares me the most with oxy-acetylene is the negth of the flame! Although the working distance may only be an inch or so, the whole flame can be 20 inches long, and you always have to concentrate on where it's pointing while you're studying what you've just brazed).

David



[Edited on 26/5/05 by David Jenkins]

Confession time - Im actually not a newbie as iam time served and have done this before but it was a long time ago. Advice so far is a good refresher. Thanks. More advice greatly recieved.

I also have the option of tacking the job up and getting my friendly fabrication place to finish it for me. Im not too bad with the mig (will need a little practice on some scrap to set the welder up). My main concern is that i have been advised to stitch weld it to avoid distortion and i see this stopping and starting as adding risk to getting a sealed weld. Theres probably plenty of people on here who have managed it with far less skill / practice than me. I was thinking of using the braze to seal the pin holes up so it should be easier than brazing from scratch - i hope!

Fluxed rods sound like a good idea - probs more expensive but hopefully easier to get a good job for a novice. It will probably be cheaper to get my local place to do a cash job rather than having to buy rods and gas etc.

If i silver solder the strainer back on can this be done with a good quality soldering torch ( i have one of the expensive plumbers torches - not the diy B&Q job) or do i need to use the bottles?

re. strainer: I cut out a bit of pipe, tidied up the edges so that they fitted each other as well as I could manage, then put 3 tiny tack welds round the join with my MIG. These were just to hold things in place during the next job, and to add a little bit of mechanical strength.
I cleaned everything up and finished off the joint with silver solder, which flowed into the seam to make a good seal - you could probably get the shop to braze it for you while they're at it.
Be prepared to soak the pick-up in degreaser for a while, and flush it out, as you will choke from the burnt-oil fumes while you're brazing!


You are probably right about giving the job to a local shop (if you can trust them) as they'll just do the work in a few minutes, whereas you'll take hours, and maybe cock it up!

David

[Edited on 26/5/05 by David Jenkins]

As with soldering get everything clean before starting.

For small jobs I use prefluxed rods which are available in different lengths --- you can even get short ones from B&Q or Halfrauds at a price.

[Edited on 26/5/05 by britishtrident]

The pre fluxed rods are your best bet. You want a flame with a feather on the centre, not a completely neutral like for welding and get your workpiece warm all the way round the join so the braze runs in. You could use silver solder instead if you are only using it to seal the joins.

Is silver solder easy to get hold of?

Sounds expensive!!

Probably not the best option for you - I used it 'cos I had some handy, together with some of its special flux. It works at a slightly lower temp than braze, and it's very 'runny' when molten and gets into cracks and close-fit joints. Not too expensive when bought 1 length at a time from model engineering suppliers, bl**dy expensive when bought from places like BOC who only sell 1kg packs!

You can braze the joint just as easily - but the expert would do it quicker and better than someone out of practice...

David

Buy an RS2000 alloy sump and pickup off ebay. It is a whole lot lighter and neater!

Cheers

Mark

re silver solder not that expensive B&Q Wharehouse sell it pre fluxed in the plumbing section beside the "Bernzomatic" Blow Torches.

1 turn on cylinders
2 adjust the gas pressures
3 turn on the acetylene & ignite
4 turn on the oxygen, and increase to produce a neutral flame.
For brazing, a slightly Oxidising flame is required, ie small flame cone.
For very thin metal, tig welding will give the best result, but is expensive.
Cheers John

I got the sump done in the end by;
1. Got neighbour to do the main welding,
2. I practised and got my hand back in.
3. Left sump overnight full of water.
4. Next night - light rust spots evident where water leaked.
5. Welded over rust spot area (cleaned it first).
6. Repeated 4 & 5 countless times.
7. Checked gasket face for flatness and adjusticated where necessary.
8. Thoroughly cleaned outside of sump and covered all joints with bond&seal (Wurth) for good measure (a bit overkil but made me happy).
9. 3 thick coats of smoothrite.
10. Oil pickup shortened and rejoined with JB weld.
11. Job done, refitted with new gasket and so far so good.


No brazing reqd in the end. Thanks for your help. Especially thanks to Mark Allanson for the instruction sheet - very informative.

One hint is that even though it may be water tight, it may not be oil tight.

Something to do with bubble / molecule size

Apparently a thin oil is the best thing to use to test for leaks.

Maybe that's why some website authors suggest testing with paraffin/lamp oil?

Anyway, I used water and had no problems when the oil went in - so far!

David

If it holds water it should be ok. Its to do more with surface tension, water is highly polar, so has quite a high surface tension (look at the miniscus in a thin tube of water). oil has a rather lower one, as does parrafin....(water is a smaller molecule than any of the oils)

David

But don't forget, the oil will be pressurised!
Penetrating oil is the best way to check for leaks.
Cheers John

quote:

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Originally posted by johnjulie
But don't forget, the oil will be pressurised!
Penetrating oil is the best way to check for leaks.
Cheers John

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Or your rings are f*c&ed . Not good either way. Check for leaks with a clean tissue. It'll show the slightest weep.