Shimmy1
Senior Member
I've installed a number of thumbs on excavators going back to 1979. I hadn't seen the thumb pin mounted on a boss welded to the stick before. I'm sure it works but would be a little leery of its long term life. Hopefully you guys can tell me you haven't had to weld a stick back together after a couple of years of use.
The key is to have one that has a plate that holds the cylinder mount and the thumb mount. That way, the forces applied by the cylinder are transmitted more so lengthwise on the stick rather than pushing on the tube. I've seen pics of the cylinder mount "beer-canning" the stick. Mine uses a ½" plate to hold the pin bosses, and the thumb boss is almost fully over the bucket hinge pin casting on the end of the stick. I use mine as hard as I would use a pin-mounted thumb, have been for two years. Like has been said up-thread, a pin mounted thumb is the best, but my work requires me to take my thumb on and off so often that it just doesn't work for me. I can put it on or take it off in 20 min, quicker if I have another guy to help. BTW, John C, what is your opinion of the thumb that I built?