Going to try brazing...

General cycling advice ( NOT technical ! )
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simonineaston
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Going to try brazing...

Postby simonineaston » 6 Apr 2011, 12:03pm

Amongst other things, I plan to try brazing and bread-making before I die. I had also wanted to try flying a helicopter, but have rather given up on that now... Anyway, I'm sure there's folks out there in CTC-land who could tell me a jolly story or two, on the subject of bread-making, but I'd like to stick to brazing, if that's OK!
I am NOT going to try frame-making, but will stick instead to adding braze-ons to my existing frames, and, particularly, I want to make some custom-built luggage racks. I see that mild steel tube is quite easy to get hold of these days - can anyone point me in the direction of any other suitable reources, i.e. where to get torches, gas, solder and flux etc.etc., where to get a good range of braze-ons, and maybe even direct me to an article or two about how to do it!
The odd amusing anecdote won't go amiss, either!
ttfn, Simon in Easton
(currently enjoying a Moulton TSR & a nano Brompton...)

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[XAP]Bob
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Re: Going to try brazing...

Postby [XAP]Bob » 6 Apr 2011, 12:39pm

screwfix direct?
I used school kit, no idea where they got stuff from
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
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yakdiver
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Re: Going to try brazing...

Postby yakdiver » 6 Apr 2011, 1:21pm

Forget brazing and go for a small mig welder, with a special flux-coated wire that produces it's own gas shroud as it burns.
Alias Numbnuts

tatanab
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Re: Going to try brazing...

Postby tatanab » 6 Apr 2011, 1:24pm

Not thinking about screwfix I recently bought low melting point silver solder and flux from an ebay dealer. Most modern silver solder is cadmium free, but you can still get the lower melting point ones which have some cadmium.

About 30 years ago I added a lot of braze-ons to frames and found that a low melting point silver with a normal Butane torch from your corner hardware shop was quite adequate. The thing to do, especially using silver, is keep your joint clean. Having filed and used emery paper I would then degrease the surface with IPA although meths would probably do just as well.

Braze on bits can be bought from Ceeway http://www.framebuilding.com/ who also keep fluxes etc

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simonineaston
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Re: Going to try brazing...

Postby simonineaston » 6 Apr 2011, 1:37pm

tatanab wrote:The thing to do, especially using silver, is keep your joint clean. Having filed and used emery paper I would then degrease the surface with IPA although meths would probably do just as well.

What - waste perfectly good beer on a brazing job... :wink: No, seriously, you'll have to tell me what IPA is - "something, something alcohol", I'm guessing (not India Pale Ale)
Ta for link to supplier :-)
ttfn, Simon in Easton
(currently enjoying a Moulton TSR & a nano Brompton...)

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al_yrpal
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Re: Going to try brazing...

Postby al_yrpal » 6 Apr 2011, 2:20pm

I used to brazed stuff with an Oxy acetylene torch as an apprentice. I tried to do some with a gas blowlamp and failed, they are not hot enough. Halfords sell spelter and flux.


Al
Touring on a bicycle is a great way to explore and appreciate the countryside and towns you pass through. CTC gone but not forgotten!

phil parker
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Re: Going to try brazing...

Postby phil parker » 6 Apr 2011, 2:27pm

simonineaston wrote:No, seriously, you'll have to tell me what IPA is - "something, something alcohol",:-)


Isopropyl Alcohol !

kwackers
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Re: Going to try brazing...

Postby kwackers » 6 Apr 2011, 2:34pm

Plenty of model engineering supplies have brazing/silver soldering equipment.

You need a big blow torch though. I use a Sievert torch with assorted heads and 'caravan' type propane bottle which does for all but the biggest of jobs (usually the limiting factor is the bottle freezing, in which case two bottles and a T junction usually do the trick).

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simonineaston
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Re: Going to try brazing...

Postby simonineaston » 6 Apr 2011, 2:35pm

phil parker wrote:Isopropyl Alcohol !

Doh! I knew that!
ttfn, Simon in Easton
(currently enjoying a Moulton TSR & a nano Brompton...)

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531colin
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Re: Going to try brazing...

Postby 531colin » 6 Apr 2011, 9:28pm

I use silver solder in preference to bronze brazing because its so much easier to get up to temperature with a fairly ordinary gas torch (no oxy.).
Supplies...Axminster tools (Google) for the solder (low melting point) and "Tenacity 5 " flux...best flux in the world, and good for stainless too.
Blowtorch,, Screwfix (I think), called something like swirl flame torch for brazing...can't remember the make, get back if you can't find it and I'll dig it out. The gas is important, use MAPP gas it burns very hot. The postal merchants don't do gas any more (probably the carriers don't fancy it), but its in Halfords and B&Q. Torches in B&Q as well, I think.
I find the opposite to what somebody else said, cleanliness is less of a problem with silver than soft solder...get it red hot, the flux runs in, carrying all before it.
Surfaces need to fit well, though, its not strong over big gaps.
TIPS
put the flux on, then start heating to run the flux into the joint. Get the work hot enough to melt the solder, dont use the flame to melt the solder.
Blackening of the flux means either the flux is exhausted, ie too much muck for the amount of flux, or more commonly in my case, you have overheated the flux.
If you search my posts you will find photos of my home made cable stops and disc brake mountings, or again I can look when I've a bit more time.
cable stops http://forum.ctc.org.uk/viewtopic.php?f=5&t=37462&hilit=+cable+stops
disc brakes http://forum.ctc.org.uk/viewtopic.php?f=16&t=35927&hilit=+disc+brakes

EDIT torch is BERNZOMATIC make
Last edited by 531colin on 7 Apr 2011, 2:38pm, edited 5 times in total.

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DaveP
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Re: Going to try brazing...

Postby DaveP » 6 Apr 2011, 9:44pm

And afterwards, make yourself a few buns.
Kneading dough is an excellent way to get all that grime out of the creases in your skin :lol:
Trying to retain enough fitness to grow old disgracefully...

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Greybeard
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Re: Going to try brazing...

Postby Greybeard » 6 Apr 2011, 9:44pm

For brazing proper you really need oxy-acetylene bottles and torch. Not cheap to set up - my cylinder rental is currently 120 quid a year for the smaller sized bottles (about 2ft tall). Add on the cost of the torch, flashback arresters, guages etc and you're looking towards thick end of 300 quid to get going. It all depends on how much you're going to use the stuff - I do a few vintage bike restorations and occasionally play around with old cars/motorbikes and maintain/skipper a 65ft long square rigged steel sailing barge from 1923 for a preservation society :shock: so at a push can almost justify the expense.
It is possible to get a hot enough flame from carbon arc rods running off an electric welder - but there's no real control over the flame for fine work and there's a serious risk of eye damage from the UV light without a proper mask and adequate care. Silver solder is cheaper to work with as a good propane torch will get things hot enough, though I'd not want to trust it for brake mounts :roll:
MIG/TIG welding is great - if you're skilled at it. I must admit I've never really been able to master it for fine stuff :? And you still have the outlay for a gas bottle unless you buy the small and expensive disposable jobs.
Steve

rjb
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Re: Going to try brazing...

Postby rjb » 7 Apr 2011, 9:15am

Note for the "mods" - can you put this post in the "tech too good to loose" section when members have exhausted it. :wink:

Also the previous post with colin531's excellent comments concerning fork rake :wink:

Should we just put colin in the technical too good to loose section - then we can access him at anytime :lol:
At the last count:- Focus Variado, Peugeot 531 pro, Dawes Discovery Tandem, 2 Dawes Kingpins, Raleigh 20, Falcon K2 MTB dropped bar tourer, On One Pompino, Longstaff trike conversion on a Falcon corsa. :D

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simonineaston
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Re: Going to try brazing...

Postby simonineaston » 7 Apr 2011, 10:28am

Gosh - seems there's a 50 / 50 split between Fans of Welding and Fans of 'silver-soldering' !
I've found this interesting site... http://www.jm-metaljoining.com/technica ... ectionid=1
ttfn, Simon in Easton
(currently enjoying a Moulton TSR & a nano Brompton...)

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531colin
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Re: Going to try brazing...

Postby 531colin » 7 Apr 2011, 10:37am

Well, I'll say you can simply undo silver soldering by re- heating it, and you are least likely to damage anything as the temperature is low.
Welding is a very skilled business, if you need it done well. I would hesitate to weld something myself if my life might depend on it being right....like bike stuff! Too hot, damage the tube, not hot enough, it won't stick....then again, my welding is sh!te!

EDIT some tubing eg 531, will be damaged by welding temperatures. If the tubes are welded together to make the frame its fair enough, but I wouldn't weld a frame that is lugged and brazed, or fillet brazed, unless you really know about the tubing.