Silver soldering brass and steel - Advice needed.

[AESamuel]

Hi there!

I'm making a small (stanley 271 size) router plane and would like some advice on how to connect the brass and steel together.
The construction will be very simple, a mild steel base (50x70x5mm) and a brass block (13x25x75mm pre-shaping) drilled out with two holes, one for the blade and one for a thumb screw, with the brass block soldered directly on top.
Here's my questions which I would be grateful if anyone could answer!

I have two butane torches which I have used to harden the tips of tool steel, are these likely to be hot enough for the job? I could construct a basic hearth with a vermiculite base and some household brick walls to help alleviate the heatsinking of the metal.

Would "plumbers" grade flux and silver solder work or should I be looking more at something like silver-flo and some thinner silver wire? As an add-on, will silver solder be strong enough or do I need something like silver braze?

Do I need to create a gap or relief in the joint for the solder to flow or should I keep the joint flush?

Many thanks again in advance for any help

 

[CHJ]

These are the basic constituents that I use:-
1. Vermiculite? Tiles for base and side insulation and a glass/ceramic? wadding mat hearth.
2. MAP Gas fed hand torch, with additional butane/propane torch if extra heat volume needed.
3. Silver Solder Wire
4. Borax powder flux (mix with water)

No need for joint fillets just clean contaminant free surfaces smeared with flux.
Solder will flow through joint with capillary action.

 

[Normancb]

That's a fairly hefty lump of brass to be soldering or brazing. You might get away with soft solder as it's a large area and relatively low stress - also less likely to cause distortion than would silver brazing. If you go that route you'll need a better flux than plumbers resin to solder to steel - Bakers fluid is the one to go for. I'd flux and solder ("tin") the two surfaces then put them together with more flux and heat again to form the joint - works better than capillarity over a large area.

If you decide to silver braze then you'll need a lot of heat for that size block - and very good insulation. Have a look at the web site for CuP alloys - lots of advice there.

DON'T use house bricks as hearth material - they can contain quite a lot of moisture which boils and can send fragments of brick flying - you can get proper firebricks or use vermiculite blocks or ceramic blanket - lots of advice on CuP site.

You can use plain borax as a flux for silver brazing, but I wouldn't - it doesn't melt till 740C. You are much better off with proper flux - melting will turn the flux clear at the point where the work is hot enough to braze. Always let the work melt the alloy, not the flame. Easyflow flux is fine, or HT5 if you want a bit more time to play around. Standard 455 (55% silver) alloy is the one to go for. You can get it in thin sheet form which you can sandwich with plenty of flux in the joint then heat to melt. Or just use normal wire - capillarity is effective at brazing (650C temperatures).

Good luck

 

[AESamuel]

Thankyou both for your replies!

It looks like I'd need to get a few more things together before attempting to solder the plane together so I think I'll go with my original plan for joining the body and sole. I'm going to use machine screws through the bottom of the sole then grind down and peen the heads flush.

Again, many thanks for your advice.

 

[Phil Pascoe]

If you change your mind PM me your address, I'll send you flux and brazing rod more than enough to do your job. I'm only in Carharrack, but at present picking it up isn't ideal. A mere £2 in the lifeboat.

 

[AESamuel]

If you change your mind PM me your address, I'll send you flux and brazing rod more than enough to do your job. I'm only in Carharrack, but at present picking it up isn't ideal. A mere £2 in the lifeboat.

That's very kind of you!

 

[hawkeyefxr]

If you do go the Silver Solder route do not use a lot of the silver solder, the tiniest bit will seep into the joint. There should be next to nothing to clean off. When the work piece is hot enough it will run like water. Do not try to 'build' it up like a weld on brazing.

 

[bourbon]

I see Brenton West on the repair shop does this. He makes it look really easy. I'm betting it's not!

 

[CHJ]

I see Brenton West on the repair shop does this. He makes it look really easy. I'm betting it's not!

The secret is clean surfaces, and subject material up to solder temperature all the way through.
As Hawkeyefxr says once temperature is achieved the solder will flow like water as soon as it touches the work.

Getting the heat all the way through the piece is the hard part if it's a heavy block, don't be tempted to solder just because the surface nearest the heat source is hot enough.
The cost of the gas and patience becomes significant with DIY torches .

 

[hawkeyefxr]

Then lathe tool rests soaked up the heat lol. If you have big pieces of metal surround the job with bricks, it will be like a mini furnace.
Been using silver solder since i was 17 and used some just last year, i'm 71 now lol

 

[CHJ]

Biggest hunks I ever handled were 9" cubes of Brass Waveguide Chokes for low frequency Radar, fitting attachment flanges, think they used more natural gas than a weeks household cooking.

 

[hawkeyefxr]

9in cube!! jeez they were heavy i bet. Not silver soldering but cut up an 8ft x 4ft x 4in plate steel.

 

[CHJ]

They ended up somewhere underneath this little baby.

 

[Dalboy]

If it is a large piece but does not require to much strength then try a low melt silver solder which does not require so much heat