DarrenW
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| posted on 26/5/05 at 08:07 AM |
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Brazing - how do i do it?
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!!!
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Nisseven
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| posted on 26/5/05 at 08:42 AM |
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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.
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David Jenkins
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| posted on 26/5/05 at 08:58 AM |
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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
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flak monkey
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| posted on 26/5/05 at 08:58 AM |
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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
Sera
http://www.motosera.com
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David Jenkins
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| posted on 26/5/05 at 09:02 AM |
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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]
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DarrenW
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| posted on 26/5/05 at 09:21 AM |
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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?
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David Jenkins
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| posted on 26/5/05 at 09:34 AM |
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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]
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britishtrident
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| posted on 26/5/05 at 09:37 AM |
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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]
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Peteff
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| posted on 26/5/05 at 10:00 AM |
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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.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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DarrenW
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| posted on 26/5/05 at 10:02 AM |
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Is silver solder easy to get hold of?
Sounds expensive!!
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David Jenkins
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| posted on 26/5/05 at 10:12 AM |
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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
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mookaloid
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| posted on 26/5/05 at 10:52 AM |
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Buy an RS2000 alloy sump and pickup off ebay. It is a whole lot lighter and neater!
Cheers
Mark
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britishtrident
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| posted on 26/5/05 at 01:51 PM |
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re silver solder not that expensive B&Q Wharehouse sell it pre fluxed in the plumbing section beside the "Bernzomatic" Blow Torches.
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johnjulie
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| posted on 9/6/05 at 09:06 PM |
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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
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DarrenW
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| posted on 10/6/05 at 08:52 AM |
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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.
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stevebubs
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| posted on 10/6/05 at 06:48 PM |
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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.
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David Jenkins
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| posted on 10/6/05 at 06:52 PM |
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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
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flak monkey
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| posted on 10/6/05 at 06:55 PM |
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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
Sera
http://www.motosera.com
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johnjulie
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| posted on 16/6/05 at 09:24 PM |
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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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MikeRJ
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| posted on 20/6/05 at 09:38 PM |
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quote:
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
If the oil in the sump is pressurised your crankcase breather isn't working very well!
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Peteff
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| posted on 20/6/05 at 10:10 PM |
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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.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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