Hey folks - I'm finally getting used to my 580 Super E - and I'm realizing that I really need a thumb. I'm not dishing out the dough to buy a pre-manufactured thumb - I'm going to make my own. I'd like a hydraulic, but at this point I'll settle for a fixed thumb that I can make hydraulic later. I have access to a cutting shop so I'll get them to cut the parts for me and I'm going to weld it together. My question is - where is the best place to get a longer bucket pin, so I can attach the thumb there. I have also noticed that some of the pins on my machine are not greasable, why? did someone cheap out at some point and put the wrong pins in, or do some points just not need grease? (find that hard to believe). I'll mostly be using the thumb for moving wood/stumps, with the occaisional rock or two (not many rocks here) I've started a quick design in google sketchup... anything I should include/avoid? Thanks!
Oh, and the second question... mine is an extend-a-hoe.. for attaching the pin point of the thumb, I'll need to attach to the sides of the "extend-a" as there is no bottom to it (its the dipper). Is it a faux-pas to weld there, I was thinking of welding a doubler plate on each side, with a pin across the bottom. Good/bad idea? I know there are some areas that are not to be welded to - is it just the cast parts? Thanks!
Nice drawing. Don't you just love Sketchup? Your local machine shop should be able to make the pins you need. They can suggest a material but 4140 works well in most cases. It's less expensive because you don't have to heat treat it unless you want to. I've never seen a fixed thumb and it's been awhile since Ive looked at an extendahoe but if your welding plates to the side of the stick I would weld only the top and bottom of the plates. Round/chamfer the corners of the plates and stop the weld at the center of the corner. Believe it or not, the arm needs to twist through its entire length. If you weld at right angles to the length of the arm [like the sides of the plate or all the way around] you'll dam up the stresses at the weld and you'll start to see cracks. That's just my experience- don't take my word for it.
Good info - thanks! I totally understand about rounded corners, and it makes sense only welding on two, not four sides. I'm not actually welding to the dipper arm, there are two "guide arms" (for lack of a better term) that are outside the dipper - not exactly sure what their purpose is, other than it must be stronger because they are further out from the center of the arm. I'll post another pic to clear things up (when it's light out!)