View Full Version : Advice needed on bonding dissimilar metals

04-27-2009, 02:07 PM
I need to make a bond between some 12L14 steel and 1/4" drill rod. The drill rod will take some light impacts that would drive an non bonded rod, back through the steel.

The drill rod passes through the steel for about a 1/4" in distance. I feel the fit is too loose for use of a Locktite product (originally specified). I also wish to preserve the finish on both parts if possible (no high heat).

Would the use of a silver solder be advised? Is there a better suited product I should consider? Brazing heat seems too high? I have oxy/acet available. Mechanical fasteners are out.


04-27-2009, 03:52 PM
An interference fit will do the job if you heat the part with the hole to several hundred degrees and chill the other with dry ice or LN2. You can get about a .002" interference as long as you don't need to pass much of the rod through the hole. That's enough for it to stay put as if it were welded. It works on crankshafts.

04-27-2009, 04:17 PM

If I understand you correctly, you have a 12L14 artifact with a hole that is a loose fit over a piece of drill rod.

You can certainly solder that with silver bearing solder.
You can certainly silver braze that.

Silver Brazing is possible to achieve strength of 30k - 60k psi.
Silver bearing solder not as great but not to be sneezed at either.

Both require use of a flux, that either flux will dull a polish but will leave your materials without significant surface oxides, if you do it right.

Temps for Silver bearing about 500^F
Temps for Silver braze about 1200^F

Hth Ag

loose nut
04-27-2009, 08:30 PM
Check with your supplier on silver soldering, some of the lead bearing steels cant be done the lead screws it up.

04-27-2009, 08:48 PM
You say the fit is too big for loctite, does that include the 660 grade stuff which will work with a gap of .5mm or .02"? I've used this with "sloppy" fits before and it works well.

04-27-2009, 09:25 PM
Thanks to all who responded.

Although the actual application involved multiple fitting pieces for proper alignment, I tried to simplify the scenario in order to make it understandable. Today I went down to my local welding supply house, parts in hand and was directed towards 36% silver solder. Took about 20 minutes to set up and about 15 seconds after that I was done. Works great.

Plan "B" for me was Evan's suggestion, with an oversized drill rod turned for the hole.

No, not familiar with Locktite 660. My gap was about .02 at worst, but I never could generate any trust for that type of adhesive in a gap situation and was further spooked by worries of viscosity with a perfect set of meshed fine threads underneath the glue point.

Again, thanks to all who responded.


04-27-2009, 10:39 PM
Was about to say Easyflo 45 or equivlent with solder rated at 1200 deg. What I use for my locomotive. Even bought a nice Sievert propane torch.

04-28-2009, 04:15 AM
Glad it worked out. For reference Loctite 660 is a paste rather than a liquid. I've used it in gaps around the size Loctite specify and slightly larger with no slippage at all. Once it has set almost nothing will remove the part.

Many years ago I had a problem with an old drill press where the taper was so stuffed up that the chuck would not stay on despite what I did. At that stage I had no lathe to true things up so I used a smear of 660 on the arbor - gave it a whack with a soft hammer and let it set for a couple of hours.

Since then the drill has been (a)bused beyond belief by others but the chuck stays put despite jamming on 1" drill bits and worse.

04-28-2009, 12:18 PM
Thanks for the information, Gavin, and the example. I'll have to pick some 660 up for a try. I'm sure I'll have a need at some point in time!