Questions about flux for silver brazing

[filthyd]

Hey guys,

I've been plodding along trying to build my first lugged steel frame. I have been practicing brazing using 45% silver brazing rods and Stay-Silv Black flux (active 1000-1800 degrees F). For some reason though, I can't seem to get the tubes hot enough to melt the silver and draw it through without charring the hell out of my flux. Generally, when it's getting towards green, the tube is just approaching the temperature I need melt the silver. However, most of the time it turns black and is stuck on the tube before I can get the silver to melt. So I pose my question to you all: what flux do you use for silver brazing (i'll be using 56 and 45% rods)?

Also, I am a total newb and do not have an oxy-acetylene torch (nor the funds for one). I've been using a MAPP air torch that seems to get things more than hot enough, though I know it's not totally ideal.

Thanks for any and all suggestions.

Darius

[e-RICHIE]

You are going to have to lose the MAPP gas, find the funds, and use a proper oxyacetylene torch setup atmo. I know some folks
use the black flux but I don't recommend it. I use Handy + Harmon white paste flux (Handy Flux??). PS why the variations in rods?

[filthyd]

I bought the cheaper rods to play around with brazing. I'm following this book and the author suggests using 45 for the BB lug and 56 for the rest of the joints. Is there no way to do it with MAPP? I know oxy-acetylene is much, much preferred, but is there no way with MAPP?

I'll take a look at that flux. Thanks again for your help!

Darius

[filthyd]

Also, should I be heating the joint very slowly (i.e. like 5-10 minutes to achieve the desired temp)? It's taking me about 1-3 minutes to get the joint to temp. I've tried applying more flux as my flux becomes exhausted and continuing to heat, but it still exhausts by the time I get the joint hot enough. I know I can pull the silver through just fine, but it's going to be a mess cleaning up if I do it this way.

[EricKeller]

use the Mapp torch to burn the book and then set the torch aside for the next time you need to do some plumbing.

Strangely, one of the problems people seem to have with low-energy gasses is overheating. Your best bet is to bring the joint up to temperature quickly, but evenly and under control. Shouldn't take 10 minutes. Don't know what else to say about it, but the torch is holding you back. I almost wonder if you don't have the wrong temperature flux. There are varieties of flux and each has its own activation temperature. Some of the Harris fluxes are for lower temps than needed for silver brazing. My LWS is not up to speed on brazing, it's not widely used any more and so they aren't being educated about it.

[Will Outlaw]

I bought the cheaper rods to play around with brazing. I'm following this book and the author suggests using 45 for the BB lug and 56 for the rest of the joints. Is there no way to do it with MAPP? I know oxy-acetylene is much, much preferred, but is there no way with MAPP?

I'll take a look at that flux. Thanks again for your help!

Darius

I built #1 and #2 with MAPP, 56% Safety-Silv and Harris Stay-Silv white so it's certainly possible, although not ideal.

It takes a while to get the lugs up to temp but it works ok. Practice makes perfect (well, better), keep the thing moving and you'll get a feel for it. Working with some practice rings cut out of cheap 4130 helps get the heat control a little more dialed in too.

With MAPP it feels like it takes a while to get things back up to temp once you move the flame elsewhere but with patience you can pull the sliver through everywhere, even that damn bb shell, and not exhaust the flux.

I also did the seat-stay fillets and cable stops on #1 with 45% because that's what I had laying around. Worked fine with a cheap MAPP torch and I really didn't notice one being particularly more challenging than the other. (although that 56 sure flows nicely.)

I have an oxy/acetylene rig coming on semi-permanent loan from a buddy because I was going to go broke buying canisters and I have some thick plate drops for #3 that I don't think MAPP will be able to handle. But you could look into renting/borrowing one for a bit if you're just doing one frame.

[Andrew R Stewart]

One of the issues with flux is the time at temp. Longer seems to use up it's qualities. Another aspect that i have seen with newbies is with a low heat torch the tendency to dwell on one spot while getting up to temp can cause that spot's overheating. An irony but true.

I agree with the advice to get an OA torch set up. Until then try a few practice games. Prep and flux a practice piece. bring it up to temp and then let it cool off without adding filler. Just to watch the flux change it's look. It should get all glassy and shinny clear then stay that way as it cools. It should disolve off in warm water quickly.

MY limited experience with 45% silver is that's it's gummy and will not flow like 56%. The tendency is then to add heat to the fill spot and flux burn off is likely. Try practicing with 56%. Also practice with brass/bronze. That is a higher temp rod and flux so you will begin to get comfy at the lower temp of 56%. Most of your issue is with heat control and you need to play with that. Is there some one that can look over your shoulder?

The last thing I'll say is the book you are following is not held in high reguard by many. Not that it is wrong, just that others seem to explane/guide/start out newbies with a better aproach. Andy.

[filthyd]

Thanks for all the advice, guys. I'm going to practice with heating the joint evenly, perhaps get a different flux, and see if I can get my hands on an OA torch. Also, the 56% silver I ordered is coming in this week, so that will hopefully make things easier too.

[suhacycles]

So far I've managed to do 5 frames using two Bernzomatic JTH7 torches clamped together. Yeah, it does heat up things slower and the flame is very broad but it does the job. My favorite flux to use is the Fred Parr stuff (lasts longer and comes off easier) and some 56% silver which flows quite nicely under that kind of heat... the 45% not so much and you risk burning things more. Using lots of flux doesn't hurt and I usually dip the silver in some as well.

[echelon_john]

I use MAPP/Chemtane+Oxygen with no issues. I think Circle A does too, and a number of others. Plenty of heat to get in and out quickly, even on heavy steerers/thick dropouts. I don't recall the exact numbers, but I think the difference between OxyMAPP and OxyAcetylene is about 400 degrees; one burns at, say, 4700 degrees, the other at 5100. Something like that. I know the flames have different physical properties as well, but both are perfectly workable with practice IMO.

[prolix21]

Also, should I be heating the joint very slowly (i.e. like 5-10 minutes to achieve the desired temp)? It's taking me about 1-3 minutes to get the joint to temp. I've tried applying more flux as my flux becomes exhausted and continuing to heat, but it still exhausts by the time I get the joint hot enough. I know I can pull the silver through just fine, but it's going to be a mess cleaning up if I do it this way.

You want to keep your heat cycle as short as possible. Get everything up to temp, get it brazed, get out of there. The more heat you pump into a join (and the more time you do that) causes more distortion as well.

[EricKeller]

I use MAPP/Chemtane+Oxygen with no issues.

this is not what the OP is talking about, and the book he has does not involve an oxy/fuel torch either. Oxy/(any applicable fuel) is fine, but the cost is on the same order as oxy/acetylene. Not sure how long one of those plumbing sized mapp bottles would last in an oxy/fuel setup though

[echelon_john]

My bad--thought he was talking about mapp/o2 and folks were saying that acetylene/o2 was markedly better.

this is not what the OP is talking about, and the book he has does not involve an oxy/fuel torch either. Oxy/(any applicable fuel) is fine, but the cost is on the same order as oxy/acetylene. Not sure how long one of those plumbing sized mapp bottles would last in an oxy/fuel setup though

[Stellate]

Hi Guys,
I`m also a newbie to brazing and silver solder. Although experienced in TIG no help here :(
But I want to try my hand at brazing or silver solder.

I`m building my steel lugged frame Reynolds 731OS and would like to braze it or silver solder? What are your recommendations?
I also need some guide in what rods i should use, size, type and what flux to use with the matching rods.
I`ve read in the previous post about 56% and 48% rods but are their names for these rods?
I`m in Melbourne Australia can i by these locally, or order over the net only?

Also if i were to build a frame using fillet braze process what rods and flux should i use here?
Also can some give advice if the BB should be brazed using a certain rod and flux?

Your advice much appreciated
Alex

[e-RICHIE]

Hi Guys,
I`m also a newbie to brazing and silver solder. Although experienced in TIG no help here :(
But I want to try my hand at brazing or silver solder.

I`m building my steel lugged frame Reynolds 731OS and would like to braze it or silver solder? What are your recommendations?
I also need some guide in what rods i should use, size, type and what flux to use with the matching rods.
I`ve read in the previous post about 56% and 48% rods but are their names for these rods?
I`m in Melbourne Australia can i by these locally, or order over the net only?

Also if i were to build a frame using fillet braze process what rods and flux should i use here?
Also can some give advice if the BB should be brazed using a certain rod and flux?

Your advice much appreciated
Alex

Most 56% Ag filler rod conforms to AWS standards and is referred to as Bag-7 (I think...) so no matter who supplies it,
the differences will be minimal atmo. I use it for everything except dropouts. At the core, it's mostly about interference
fits and torch deftness.

[Will Outlaw]

Most 56% Ag filler rod conforms to AWS standards and is referred to as Bag-7 (I think...) so no matter who supplies it,
the differences will be minimal atmo. I use it for everything except dropouts. At the core, it's mostly about interference
fits and torch deftness.

Hey Richard, what's the reasoning for not using silver for dropouts? And are you talking about both the front and rear drops?

I seem to recall you or someone saying it had something to do with strength (silver being maybe too strong?) but don't remember exactly.

Just curious.

[e-RICHIE]

Hey Richard, what's the reasoning for not using silver for dropouts? And are you talking about both the front and rear drops?

I seem to recall you or someone saying it had something to do with strength (silver being maybe too strong?) but don't remember exactly.

Just curious.

On one hand, it's habit and what I know. I am more comfortable with it - period. I also think that the dropout joints need a certain about of ductility, or flex (not sure what the correct tech term would be). The parts take a lot of impact and I think a high strength joint there is not a good thing. That is not to suggest that a brass brazed area is a low strength joint. But there is that stateside mentality that "silver is better" and "less heat is better" etcetera. I can't process that since I was weened on brass brazing for all frame processes. By extension, it's also why I would never use silver for canti studs. Sooner or later, the join will crack and fail. It's only a matter of time. I wouldn't want to court that situation on frame ends.

[Will Outlaw]

On one hand, it's habit and what I know. I am more comfortable with it - period. I also think that the dropout joints need a certain about of ductility, or flex (not sure what the correct tech term would be). The parts take a lot of impact and I think a high strength joint there is not a good thing. That is not to suggest that a brass brazed area is a low strength joint. But there is that stateside mentality that "silver is better" and "less heat is better" etcetera. I can't process that since I was weened on brass brazing for all frame processes. By extension, it's also why I would never use silver for canti studs. Sooner or later, the join will crack and fail. It's only a matter of time. I wouldn't want to court that situation on frame ends.

Got it. Thanks!

[Oldbikerider]

I`ve read in the previous post about 56% and 48% rods but are their names for these rods?
I`m in Melbourne Australia can i by these locally, or order over the net only?

Alex

Alex,
I get my 56% silver from Ausweld who are a local Harris agent. 56% Bare Silver Brazing Alloy x 10 rods | | AusWeld
They also sell other rods as well as white brazing flux and the Harris black high temp flux.

Graham.

[Kumo Cycles]

I`m in Melbourne Australia can i by these locally, or order over the net only?

I like to use Cycle Design Flux and rod, really good quality stuff. PM me and I can sell you a little to get you started