[Edit: can't I intersperse images within a post at this point? Can't attach more than three? I'm giving up and leaving them as attachments, which happened without my wanting it to.] A few months of intermittent attempts to disassemble this have gotten me nowhere. Photo 1 shows the 'ears' of a thumb I had to customize a couple of decades back, in order to mount it without severe underbite. Machine shop did a decent job of aligning/ line-boring the new bosses on the thumb, and I don't recall having too much difficulty installing it. But it was doomed to freeze up at the pin-to-boss locations, since there's no relative movement there to keep it from getting rust-bound, and never a way to lubricate or otherwise combat rust. So here I am 20 years later trying to get that pin OUT, in order to get the QD coupler (above it, partially visible) out for some similar rust-related descaling and long-deferred maintenance. Photo 2 - you can see that I've managed to drive the pin out by maybe a half inch. To do even this much, I bought a 20-ton hydraulic gear-puller and have been heaving on it, while lubing the pin wherever I can find access. The tiny hole at top of ear was something I drilled for this purpose, but I'm not convinced any oil is getting into it. (I figured I'd eventually drill out the outer portion and thread it for a grease nipple, to help prevent this epic from recurring.) When I couldn't drive it any further, I moved the hydraulic puller to the other side, thinking the pin would be all too happy to slide back through the newly-lubricated boss, and maybe keep going the other direction. It was having none of it - didn't move AT ALL. So I returned the puller to the original side and heaved on it some more, because...well, what else IS there? The only perceptible result was that the puller's link-holes are now ovaled out, and the (fake) 8.8 hardened bolts are now half bent (I found I could cut one with a hacksaw, ergo "fake.") The pin moves quite freely through the dipper-front bushing - I can slide the whole thumb right/left. But I'll be damned if I can get useful movement between the pin and the thumb's bosses. My only working theory is that the ears have very slightly spread from use and maybe my recent efforts, so the pin is binding on bosses that are no longer on axis. Is that a thing, or paranoia? I have also intermittently used heat (though I have only propane) and impact (from a rotary hammer fitted with a ground-rod driving bit.) None of these methods have been encouraging. Also, heat-vs-lubrication concerns me, too (all I need is a bunch of burnt lube residue in there to help me out, right?) Photo 3 shows more of the QD coupler. Rust isn't so bad in this underside view, but the hydraulic cyl looks from the top like it's a few uses away from springing a rust-caused leak. I spent weeks struggling with THIS item, and never got a single pin to budge at all, concluding that the only way to deal with it would be on its side in a press - maybe. That's when I started working on the thumb-pin. View attachment 354244 So WHAT TO DO? Ideas? Cut the ** inside the ears - along with my losses - and get a new pin made up? If a new pin, what to do to prevent recurrence? Stainless? (Would that last as a bucket pin?) Mahalo... Dave
Last time we had a seized pin to get out it took 90 tons and a hole blown through the pin with a lance before it started to move.
Do you have any way to drill into the pin center from the side? The bigger the hole the better and then fill it with weld to shrink it a few thousandths? As mentioned, another alternative is to cut the pin between the ear and on each side of the bushing link so you can work each side independently. This effectively doubles the pulling power as you work each pin bit. Can also help you lay on side to better drill each one out if needed to try and weld-shrink them a bit. Since I'm just tossing stuff at the wall to see what sticks, if you're able to drill a decent hole, tap it and use a good bolt to put lot of pull on it while you heat it/smack it from the other side. May need a rosebud with acetylene to do anything with heat. Lastly, to give a healthy nod to 92U, there's lots of cool videos out there on how to make your own thermal lance. Why not have a little fun experimenting fun?!?!
Turn the pin to liquid steel with a lance, drive it out and get a new one manufactured. You could possibly modify the design of the ears to allow the pin to be greased even though it doesn’t rotate relative to them.
I fully understand this was 20 years ago when you fitted it, but something I've learned in a lifetime, I have a hard and fast rule for things that don't move, such as that pin in that pin boss, that is, if it doesn't get Loktite it gets Never Seize. As mentioned previously, thermal lance will do it every time, but not everybody has one. Heating the two outside pin bosses with a rose bud until they're red hot, that typically allows the BFH to move the pin. But yeah, we've all been there.
I had this only once and cut the pin. You have plenty of room to get in there. Joe H
Yeah, I think take a Sawzall and cut the pin on each side so you can then lift the the middle assembly up to get the middle part of the pin out.
I used a diamond wheel, sawzall wouldn't touch it. Joe H
Could depend on the type of steel. Someone good with a torch and a big tip could cut it. I wouldn't recommend a torch if you don't have experience cutting thick steel. Easy to cut into other parts you don't want to. Best way would be to heat as much of the circumference of the pin as possible red hot and then proceed to make a straight cut across the pin. I watched a welder do this on about a 3" shaft and the cut was smoother than a saw cut!
It's likely worn / has a groove. I would also cut it and then press or bore out the individual pieces that you have left. It will be a lot easier to deal with in smaller pieces.
Don't know how deep of a cut you need to go but an abrasive cutoff wheel should get you in there easily without a lot of collateral damage. A large cutoff wheel on an angle grinder may get you in there deep enough. If not, most equipment rental shops have the portable 'chainsaw' cut-off wheels...as do most fire trucks if you have any buddies in those areas.
9" grinder& cut off wheel? Lance? Cut the thumb to access the pin. You can then heat the pin red with a rosebud tip, let it cool. It'll then cooperate. Then you need to weld the thumb back together for a new pin.
Willie has a good point if I understand what he's saying. you basically slot the ear to free up the pin, then weld it back up. Right Willie?
Stop pulling and cut the pin, relieve ear stress, and line-bore the bosses; anything else risks permanent damage. Replace with a 4140/4340 greasable pin running in bushings so the joint can move, lubricate, and survive long-term
If you have done a lot of hammering on the pin to get it as far as you did the hammered end of the pin will swelled up a few more thou. to .Bear that in mind if you cut the pin make sure you press the chunk out oposite to the way you drove it . A 100 ton porto power with good strong backs and tie rods reaching across the the thumb might do it if theres room for every thing to line up. All The gaps between the stick ,quick change and thumb ears would have to be shimmed real tight so you are in effect pushing the pin out of one bore. This said,its a lot of work with the right gear . The pin needs to be cut at this point. Just be sure what ever you use like abrasive wheels will access the cut. you might be able to grind a slot around the hardened od of the pin and saw the rest if an abrasive wheel wont make it all the way. or grind what you can and torch the rest. New pin should be 4340 htsr. induction hardened.
I would probably just cut across the boss, to free up the pin. Cut whatever you have to, to get the pin out in pieces. Then weld it up after beveling and make a new pin. I do want to try and make my own lance one of these days.
I think I'd cut the ear off to free the thumb from the dipper. Now the stuck pin in the ear is only a few inches long. Cut the pin by whatever tool you can. I find a big chain saw cut off to be hard to control, I might try a 9" grinder. That ear is now only a project, not undoable. Thumb will now come off. Do the same with the other ear. Red hot steel must cool, as it cools it shrinks. I'd heat the short pieces of pin red hot. Might take two cycles. If the ears are bushed, the hard bushings will be annealed, and shrunken, replace them.
Thanks for that. There were way more responses to my tale of woe than I'd expected, but the idea of shrinking the end/s of the pin by filling a drilled hole with weld is maybe the only method that might not require me to source (and pay for) another pin, or embark on a new repair (line-boring or similar). And I think it has no downside: If it works, I can move on with life, and if not, I can choose a weapon and (probably) cut through the pin within the large-ish gap just inside the ears. Oh, and about the hydraulic gear "puller" - it's really operating in the manner of a press, only sideways, its three hooks grappled onto one or the other ear, or the meatier QD plate that's next, going towards the center. No way to use to /pull/ that I can think of in this setting.
Why would you destroy the thumb? I think you meant cut the pin. I "hope" you meant cut the pin.....
Antiseize is definitely in the plan for reassembly. Pretty sure I had the stuff around back in the day, and not sure why I didn't use it then.
I think it's going to come to that, but first I plan to try shrinking one or both pin-ends by drilling/filling with welds (and the neighborhood with smoke...) But cutting with a saw gives me pause. I guess I need to do some test-cutting to see how hard it is. If not so hard, then I think I can get a porta-band into the gap.
I don't know that anti seize on the pins would be very effective in that application. It's being exposed to dirt and moisture on a constant basis and eventually it's going to deterioration and wash out. I think someone suggested adding a grease zerk to the thumb earlier in the thread and I think that would be a more effective long term strategy. There would be fresh grease being pumped into those bored on a regular basis, flushing out moisture and debris rather than it being collected and held by anti seize. That's just my opinion, others might see it differently.
I think maybe he meant that "assuming the bosses are no longer in alignment anyway..."?
I'm sure a porta band won't fit in the gap. A chainsaw cut off saw might fit, it'll be hard to control. Sawzall seems a good choice. I wasn't suggesting destruction. The thumb was welded when it was built, it can be welded again. Most pins in this place are either not heat treated, or they are case hardened. there is a hard shell, the core is more ductile. The pin is ruined for sure. Bushings are probably ruined. Get her done. Got some replacing to do.
I have a recent thumb. It was expensive Amulet! I was disappointed that it came with plastic bushings. Maybe I shouldn't be. A thumb doesn't see the wear a bucket might. Maybe easily replaceable plastic bushings are OK.
Hadda see for myself as to whether the P-band would fit...nope. It's been an all-day thing, and ongoing. With an ancient 500HP 9" guardless grinder (and that's not the brand name...) and my one and only too-thick-by-3/32" wheel, I ground through 90% of the camera-right side before I couldn't stand seeing the grinder's cut veering off into the boss, completely ignoring my urgings to NOT do so (sometimes they bees like that...). I decided to finish it off with a sawzall. The rest was ALSO not a piece of cake. As the sawzall neared completion, the compression in the pin (gotta be from the thumb's ears) continuously smashed the cut back together and pinched my blade, so that last bit took as long as the grinding had. And no magical "falling out" of the cut off stub ensued. I drilled and tapped it to 1/2" NC, used as much impact as I dared, heated it propane-hot, trying to extract that stupid stub using bearing against the outer surface of the boss. With full torque applied, I ran a roto-hammer against the back side through the long side of the pin. Nope. No detectable movement. Likewise for the remaining ~15" long end of the pin - also unmagically staying put. I haven't checked acetylene prices for a decade, when it became absurd (we're over a barrel in Hawaii) so I generally get by with plasma instead. No way in hell my 50A machine is going to cut through 2", though if I can get to it from two sides, and use the hole I've already drilled, there's a chance. So the 2" chunk that's stuck in the right side will remain there until I cut the LEFT side of the pin out, too, thus allowing the thumb to drop away on something other than my foot. I can't cut it today. Not only is my spirit broken, with Sunday mostly frittered away in non-progress, but I first have to procure a 9" wheel that will or might fit in the 1/8" gap I've got remaining on the "other side" of the pin.
A welder with a truck could torch the pin out on both sides in short order and save you a lot of grief. The original design may not have allowed enough clearance between the bosses and the pin. You probably want about 5 thou. clearance. The pin should freely rotate when installed. Might take a little force to turn but shouldn't be super tight.
Yes, a little /clearance/, please! Good news is that the porta-band was a fit on the "other end" of the pin, and it took a mere 15 min or so to have the b*****d cut away. This also begs the question of what the pin was made of...I'd have expected it to cost me at least a couple of bandsaw blades, but it's actually still sharp - so maybe there's no real need in my use-case to go all out for hard/tough steel grades in my replacement? And those cut-off stubs left in the ears? One hit with a big sledge, then maybe 30-50 whacks with a one-arm sledge, and they were OUT. The innards were mostly dry as a bone. I don't know why I still cling to the belief that penetrating oil will THIS TIME have some magical ability to do what it is described to be able to do... anyway, there was a fine, dry-looking gritty brown rust residue that only hinted at grease ever having been present. The remaining central portion of the pin pretty much pushed out by hand - the bushing probably original and a bit sloppy, as well as having a ton of grease buildup in the reservoir. In poking around for a suitable pin replacement, assuming it's 4340 as mentioned by a couple of previous posters, what's the spec for the surface finish? Does plain old mill finish mean it's not induction/case hardened, so no good? If I happen to find an old hard-chromed cyl rod of that 1.75" diameter, would that suffice?
Hyd. cylinder rod makes good pins.
All The gaps between the stick ,quick change and thumb ears would have to be shimmed real tight so you are in effect pushing the pin out of one bore. This is what stopped the pin from coming out. You got the one side freed up. Then as it went further it pushed the ears apart jamming the pin.
That's what I thought, though the lack of lubrication certainly made a difference, or I'd have had the two offcut pin pieces fall out once cut free. I will see what the replacement pin does when I attempt to thread it through the two bosses...