To Gil C, (was it reply #11?)
When I sleeve-join with brass over steel (which I still do, mostly) I 'notch' the brass tube two or three times between each open end and the space between the steel rods. A "jewelers' file" set usually has at least one flat file with toothed edges. Thickness some under 1/16" is common. I use the edge to file straight across the joiner until a window is open, and usually clean the window with a square/pointy jeweler's file, then run a drill bit through by hand to clean swarf out.
Soldering, done right, shows clearly. NO excess globs outside the joint! Each 'window' gives evidence that the sweated run of solder is good, and cleanly to and past that point. The windows also 'vent' the innards of the joint so the solder isn't blown OUT of the contact area. I prefer the Sta-Clean type for this - the flux assists flow and penetration. (I've mentioned my clean-up procedure to make sure all the acid is neutralized and flushed away...) A damp paper towel also allows wiping any excess off the outside of the joint for less weight, neater appearance*, and removing 'tails' or globs outside the joint that could snag on structure.
(*- I know, I know: most such joints are inside structure... but I see them, don't I?)
This sounds like it takes a long time, but doesn't, really. Longer than just jamming some pieces at each other and pretending to solder them, yes, but I haven't had a joint made this way fail.
I also came across some K&S thick wall aluminum tube, about 3/16 OD, if I recall aright. The ID is a lovely fit to a 4-40 tap drill... pushrod end-fittings made up of 1 1/2" or so of the thickwall, threaded 4-40, mounted into 3/16"ID Al tube, is still going great. ...no fairlead needed, either.
Method: roughen the tapped section of the thickwall tube, by rolling it between two medium fine files. You get practically a diamond knurl appearance if you do it right. Clean oils, etc., off the 4-40 wire to the horn fittings and the inside and outside of the outer tube and the thickwall end piece. Prep some slow JB Weld, apply it to the tang, and run that into the threads, to about 1/4" from the end inside the outer pushrod tube.
Wipe some JB Weld inside the outer tube w/toothpick or some such. Butter the outside of the threaded thickwall tube LIGHTLY with JB Weld and slip it into the outer. Wipe off excesses w/rubbing alcohol.
Drill 1/16" through outer and inner Al tubes where that last 1/4" or so leaves only Aluminum to go through. Apply JB Weld in the drilled hole, and force a length of 1/16" Al tube or rod through. This is, in effect, a retaining rivet. Peen the ends close to the outer surface. When the JB is cured, file down close to - but not cutting into - the outer.
Works for me, anyway...