Silver Solder Hypodermic Stainless to Stainless

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I'm needing to join some 0.0355 OD", 0.004" wall hypodermic stainless to an existing nozzle that is 0.040" ID.  This is a brass nozzle with a stainless insert that is less than 0.080" diameter OD and swagged into the brass.  Actual soldering will be stainless to stainless.In the custom tips I'm making, it is possible that we will have breakage, due to impacts.  So my thoughts are to do a silver solder fillet.  This would allow me to heat up a broken tip and push a 0.040" rod in to push the tubing out and solder in a new piece.I'm looking for recommendation for silver solder to use and the proper flux.  I'm wanting very small solder diameter, as this will need very little solder.  Any recommendations from those that have done fine work like this would be appreciated.Also interested in other viable options that people may think.  My initial prototype to proof the idea was done with JB Weld worked into the 2 thousandths gap.  This held up fine, until I crashed the head and snapped it off.     The reuse of the tip with JB Weld is very hard.AHP AlphaTIG 200DX (2nd Gen)Lincoln WeldPak 3200HD Bird Poop GeneratorLotos LTP5000D Plasma Cutter
Reply:Might try asking on a jewelry forum.
Reply:I make custom nozzles for a piece of liquid filling equipment at work out of nearly the same material..  I'll have to look up the grade, its a high silver content with pink fluxAWS 17.1, D1.1 and ASME IX (GTAW)Miller Syncrowave 350LX, Maxstar 150sth, Maxstar 200DX and  Millermatic 252 w/ Spoolmatic 30aMiller buzz box with Lincolin TombstoneThermal Dynamics Cutmaster 38
Reply:I've had good results on similar projects with Stay-Brite silver solder and Stay-Clean liquid flux from the Harris group (subsidiary of Lincoln Electric).I'd suggest wiping down the parts with lacquer thinner, air dry, fitting them together, and applying the liquid flux with a small brush.  Allow capillary action to draw the flux into the joint.  Just enough to wet the joint through is all you need.  Cut the solder wire into small chips (on a piece of tile with a craft knife).  The size of the chips should be scaled to the size of the joint and desired fillet, but maybe in this case about the size of small pieces of fish-bowl gravel or large grains of salt.  (This just sort of depends on the overall size of the joint.)Apply the solder chips to one side of the joint.  Surface  tension between the flux and the solder chips will keep them in place.  Apply the heat to the other side.  The heat will transfer through the work to the solder and melt it, and when it melts, it will flow through the joint towards the heat.  If you heat on the same side as you apply the solder the solder won't want to flow into the joint but remain on the surface.Apply the heat gradually or the liquid flux will boil too quickly and tend to blow the solder chips off the joint.  You can also just heat the fluxed joint to "dry" the flux and then apply the solder chips to the joint, but without the liquid surface tension, keeping the chips in place might be a balancing act.  Again, just depends on how you're set up.You can also just apply the solder direct from the roll, but this tends to use a lot more than is required to fill the joint.  Once again, just depends on your desired final result for the fillet size.Anyways, the Stay-Brite solder has worked well for me.Last edited by SdAufKla; 03-18-2015 at 11:07 AM.
Reply:Good info, thanks.AHP AlphaTIG 200DX (2nd Gen)Lincoln WeldPak 3200HD Bird Poop GeneratorLotos LTP5000D Plasma Cutter
Reply:Does it need to be non toxic or withstand temperatures?  You might consider one of the expanding fixturing alloys instead--they melt at roughly the temp of boiling water (depending on which one is chosen) and expand when they cool to grab whatever they are potting in place.  It'd make repairs and assembly super easy if it happened to match your needs.Just a passing thought in case you were not aware of the stuff.http://www.flexbar.com/shop/pc/FIXTU...CAKE-p4035.htm
Reply:This is going to be dispensing hot melt at 280-300F.  So we would make that alloy molten before we push hot melt at pressure through it and shoot out the stainless tubing.    The Stay Brite I ordered was a 450F melting point or so.  That should be fine.  I also found some jewelers pre-cut silver solder that was a higher temp (1200F I believe).  These were small 1mm x .25mm x .5mm pieces.  Most of what I read indicate that the high temp is better at wicking in thin gaps.  I think I'll try one with the low temp and one with the high and go from there.  I am putting the tip in a custom heater I built to keep the glue flowing with the robot parks.  I don't think we will get to 450F or anywhere close.  However, I would be more comfortable with something at 600F.  I'll test them both an see.AHP AlphaTIG 200DX (2nd Gen)Lincoln WeldPak 3200HD Bird Poop GeneratorLotos LTP5000D Plasma Cutter
Reply:Originally Posted by Rick_HI make custom nozzles for a piece of liquid filling equipment at work out of nearly the same material..  I'll have to look up the grade, its a high silver content with pink flux