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Silver solder/ Silver braze

Posted: Fri Jan 06, 2006 21:24
by Ron Babos
Since using a brazing rod on 4130 is generally considered a no no , would anybody know what grade of Silver solder, or Silver braze is acceptable for 4130?


Posted: Fri Jan 13, 2006 21:31
Never use on the structure that was not designed for its use. I can think
of several places silver solder or even braze (brass) is used on aircraft.
Check the Carb Air box out. On the Swift, several places on the Main gear,
Master Cyl. On the jet engines such as the P&W JT-8 engines used on the
B-727/737 & DC-9's. The bleed air ducts (stainless) use reinforcements
and dublers held on with Silver Solder. Generally, silver solder has a lower melting point than Brass. Both has been used in tight fitting areas as
a paste then heated useing induction heat procass. :)

silver brazing

Posted: Sat Jan 14, 2006 10:25
by Ron Babos
Lowell: Here's the deal. The stuffing box on the oleo is was brazed into the lower tubes of the oleo. I might add that standard flux coated brazing rod will not have much capillary action and will only stick on the upper end and not travel between the tube and stuffing box. This was the way mine was at disassembly.

The other flaw with this process is that standard brazing rod requires a heat that could could cause grain fractures in the 4130 if you get too hot. As we know , any idiot can use a brazing rod but doing it right is another story.

As a certified welder I have a problem with the brazing rod method, as I have read of one case where the box pulled out of the tube and the aircraft was rolled into a small ball at landing.

Silver brazing will , with prior flux application will flow the entire area of the box with a proper prepared joint of .002-.005 clearance. Strength is in the 70000 range. Compared to normal brazing rod which will only stick it to the rim of the tube, the silver braze will make it bullet proof. Should disassembly be required the process will be the same as now.

Since all the pistons were changed in 47 and the boxes rebrazed at that time, I don't know if the original boxes were silver brazed or standard flux coated brazing rod. I do know many airframes were built using the silver braze method and the tubes would usually break before the joint failed.

Is there any written info on the stuffing box reattachment at the time of the AD when the pistons had to be changed specifying the brazing type to be used?


silver braze

Posted: Thu Jan 19, 2006 19:42
by Ron Babos
Further study on this has shown that silver brazing is the only satisfactory method of stuffing box attachment. Univair actually does this prior to welding the fitting on the end of the tube. Not sure what Wag does in there remanufactering of the oleo.