Rivet and braze procedure?

[ddoyle]

I am building up some lock plates with riveted fixtures. The pieces will be riveted together and then brazed.
 My rivets and holes are perfect 90s to the plate and things fit really well. When I take lots of little taps it results in a pleasingly firm joint. Before I get too far down the road with them I just want to make sure that the perfection of the riveted joint is not going to work against a good braze joint? Is there anything I should know/consider before I wind them up to temp and start melting copper? If I heat from the non- joint side (rivet head side) can I expect the braze to flow into such a tight joint? Is there a very best flux to use for tight joints and mild steel?

Thanks

[Mtn Meek]

I suppose you could get the joint too tight for the brazing material to flow, but it would require the parts you are riveting together to having perfectly mateing surfaces such as you would get by lapping them together.  Even then, the scratches left by the lapping compound may be enough for the molten material to flow.

The molten brazing material flows by capillary action and the forces related to surface tensions.  It will find its way through very tight spaces.

You will be needing to heat you steel up to glowing red temps.  If you are using copper, it will need to be heated to its melting point of over 1980° F.  That's about 200° F higher than you would need to go if you were using brass.

The flux you want to use is borax--like the 20 Mule Team type.

Set your work piece so the joint you are wanting to braze is in a vertical plane.  Place a little borax along the joint.  Heat the steel on both sides of the joint until the borax starts to melt.  Place a piece of copper, or preferably brass, in the molten borax along the joint.  Continue heating the steel on both sides of the joint until the copper or brass flows.  When the copper or brass melts into the joint, remove the heat and let cool down.

The technique is similar to soft soldering except you are working at much higher temperatures.

After it has cooled, you may need to soak the piece in a pickle to breakdown the scale that forms on the steel as well as the excess melted borax.  Distilled white vinegar worked ok for me, but others may be able to suggest a better pickle.

I would also suggest you first try brazing on a test piece to perfect your technique.

[ddoyle]

Phil,

Thank you very much. My confidence is up now. I will try a couple test pieces and make sure I am doing this right by cutting them up and seeing if the braze is getting in. I was hashing about the idea of the copper so I could reheat to case harden once they are done but maybe I am better off with some hardware store brazing rods.

Cheers

[Black Hand]

I use random pieces of sheet brass or rod pounded thin when brazing and borax flux.

[jerrywh]

 What Black hand said works pretty well but pure silver will flow a lot better than brass or copper.  When I made hand forged lock plates I riveted then forge welded the part on with 1/2 pure sand and 1/2 borax for flux. Calcined borax will work all by itself. You can use copper but if I was going to do it I would use the shim method like black hand said. I doubt if copper will flow into that tight of a seam.

[Mtn Meek]

ddoyle,

If you have good temperature control during your case hardening, you can do it well below the 1700° F melting point of brass.

Experimenting with different materials will give you good experience.  Go ahead and try some copper, brazing rod, and yellow brass, and see which works best for you.

I played around with brazing rod, some 16 gauge soft brass wire, and yellow brass scrap while trying to braze a trigger guard, a butt plate, and some ramrod tips made of sheet steel.  For me, the 16 gauge brass wire was easiest to position and just the right amount of brass for the work.  I could bend it and position it right along the joint which was handy with the butt plate.

[ddoyle]

Much thanks fellas, I think your right just gotta get at it and find what works. Hopefully we get a dryish day in the next few so I can set up the bricks and have some fun. I look forward to learning to be confident with high temp solder and braze. Truly one of the skills seperating caveman from astronaut.

Appreciate your time,