Loctite, Brass & Steel

[petertha]

I was trying to solve an issue over on another forum that seemed simple enough. Bond some brass shim to regular steel. What I wasn't expecting is how problematic this would be. Here are some pictures. The parts were very lightly scuffed & squeaky clean with non-oil thinner. My first attempt was #680 retainer which is 0.015" gap fill. Next day the brass basically fell right off, yet the adhesive was hard & cured on the steel. Hmmm...

Second attempt I tried 2 different strips, one with red 'permanent' Loctite and the #680 again, this time with their primer/promoter sprayed on the brass. Exact same result. Its like the brass surface is a natural releasing agent. Just pops off when the tape is removed. Brass is about 56% copper + 38% zinc. Bronze is about 85% copper + 10% tin (both vary by alloy). Maybe its the zinc? All I know from my own experience is C544 bronze Loctite's very aggressively in aluminum. Kind of caught me off guard compared to working time steel on steel. So either 'brass' shim stock is something funky which I doubt or there is something about brass.

What am I missing? Who here has Loctited brass to steel? I did some literature searching on Henkel website, they make reference to purple based on certain conditions, but nothing in big bold letters saying their other compounds basically wont work.

 

[matthewsx]

Is this for a permanent application?

john

 

[mmcmdl]

I've got brass and steel as well as any kind of loctite . Lets see what happens when I put the 3 together .

 

[ddillman]

I don't think locktite works as an adhesive.

 

[petertha]

The objective of the brass shim material was simply to build up uniform thickness in a localized area. From an adhesion standpoint, no different expectation that a steel bearing bonded to a steel shaft. #680 retaining compound has I think ~0.015" annular gap allowance so I would have thought just binding the brass down radially with tightly wound tape would have been good clamping. The joint wasn't starved of glue, you can see its uniformly bonded & cured to the steel with the brass removed. Its standard shim stock from KBC, not mystery metal.

 

[petertha]

I don't think locktite works as an adhesive.

Sorry I don't quite understand your comment. If it was a bearing race or bushing band of the same width, whats the difference? One test strip was ~ 0.5" wide, the other was ~ 0.3"

 

[mmcmdl]

262 threadlocker stuck brass to steel . I now have a new lightweight hammer . In the past , I loctited aluminum plugs on the faces of injection mold dies to allow for center drilling and then thread grinding . Never had one fail . We would then simply shock them off .

 

[petertha]

I've used Loctite to bond thin aluminum parts to an aluminum mandrel to turn them in the lathe. In that case I had the opposite problem. Required a lot of heat to let go.

 

[mmcmdl]

I've used Loctite to bond thin aluminum parts to an aluminum mandrel to turn them in the lathe. In that case I had the opposite problem. Required a lot of heat to let go.

Double back tape works great for that application also .

 

[petertha]

262 threadlocker stuck brass to steel .

So that's the same as my 2nd test example (you can see the red still cured on the steel).
I'm starting to question the shim stock itself. I have some regular brass, will try that