Excavator thumb

[Welder Dave]

Why ought it not be welded across the stick?

Welding across the stick could potentially cause a stress point that leads to a crack. If you did a kind of half circle weld across the stick would be a much better alternative. Some people have used silicon caulk to keep water out but unless the stick is going to be digging under water all the time I can't see the stick just rusting away. A weldable primer before welding the thumb mount on could be a good option.

 

[joe--h]

It doesn't rust away, it splits when it freezes.

My old Case had several.

Joe H

 

[Welder Dave]

Maybe some weep holes would help? I bought a manual thumb about 6 or so years ago I need to mount. Too much other stuff to fix that I never got around to it. I have a different issue though. The stick isn't flat. The way the stick is welded has a long tapered piece down the middle of the inside. I need to cut a plate to go around the tapered piece so there's a flat area for the thumb mount.

 

[chidog]

It doesn't rust away, it splits when it freezes.

My old Case had several.

Joe H

Rust, it will, just give it time. Its the area that was welded inside that will rust, weld through primer, burns away from the heat so the bead will still just rust. That primer is meant to protect the rest of the metal not the weld point. Its used mainly for auto body sheet metal work and spot welding.
Never thought about the freezing issue, that could be huge in some cold areas.

 

[joe--h]

You might be right too, although mine was split from freezing but if it doesn't freeze I guess rust will get it too sooner or later.

It got kinda round, chipmunk cheek looking where it had split.

Joe H