downsizingnow48
Elite Member
There are plenty of folks who would say use JBWeld to fill up those milled holes. Not me, I tried it a couple times didn't work. But it might be worth a try given the other options are not too attractive.
Backhoe Building a thumb for a model 48 Backhoe
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There are plenty of folks who would say use JBWeld to fill up those milled holes. Not me, I tried it a couple times didn't work. But it might be worth a try given the other options are not too attractive.
texasranger556
Platinum Member
As dfkrug said, without constraining your bucket to the pin somehow, it is likely your bucket will rotate on the pin rather than the pin rotate inside the dipper bore. So that bushing idea may become necessary down the line anyway if you use your backhoe a lot.
I had considered that without tying the bucket to the pin that it would probably not rotate in the dipper as designed. Maybe I could make some square inserts and JB weld them into those bothersome retainer pin holes in the bosses after roughing up the holes on the inside. The pin could be given a light coat of grease and used as a mold to let the JB Weld conform to the pin. Then on one or more of those square inserts, I could drill and tap a hole for a set screw to jab into the pin and keep it from rotating. The challenge will be to remember that this little set screw is in there next time I want to take out the pin! Then there would be a redundant pin retaining method, in addition to the ring clips on the end. Once JB Welded in place, a small hole could be drilled into the edge and drive in a small taper pin to hold the square inserts in place forever. I must be nuts for going through all this just to be able to grease the pin from the end. Alright, I admit it, I am nuts, but I've already proven that by designing and building my own backhoe thumb.
I have used JB Weld quite a bit and it is fantastic stuff. I've made "temporary" repairs that ended up becoming permanent repairs that have never failed. It helps to add reinforcement and use the JB Weld to tie it all together. It also helps to use the older JB Weld (not the JB Quik) since it will flow and soak in more.
Off-topic: Relative to JB Quik, my son ran his VW Jetta into a branch on the road and smashed up the fiberglass frame that holds the radiator in place. We used JB Quik to patch that together and it has held up just fine now for two years. It helps that the fiberglass break has a lot of exposed fibers, so there was a lot for the adhesive to grab onto. We used up an entire set of tubes in one gluing operation requiring us to run several "dry runs" of applying the adhesive to both sides, then taking the snapped off frame and getting it into position, and timing ourselves to make sure we could get it all done before it sets up. JB Quik gives you about 3 minutes of working time once you're done mixing it up, so you have to be sure to be able to get everything in place in time.
I have used JB Weld quite a bit and it is fantastic stuff. I've made "temporary" repairs that ended up becoming permanent repairs that have never failed. It helps to add reinforcement and use the JB Weld to tie it all together. It also helps to use the older JB Weld (not the JB Quik) since it will flow and soak in more.
Off-topic: Relative to JB Quik, my son ran his VW Jetta into a branch on the road and smashed up the fiberglass frame that holds the radiator in place. We used JB Quik to patch that together and it has held up just fine now for two years. It helps that the fiberglass break has a lot of exposed fibers, so there was a lot for the adhesive to grab onto. We used up an entire set of tubes in one gluing operation requiring us to run several "dry runs" of applying the adhesive to both sides, then taking the snapped off frame and getting it into position, and timing ourselves to make sure we could get it all done before it sets up. JB Quik gives you about 3 minutes of working time once you're done mixing it up, so you have to be sure to be able to get everything in place in time.
texasranger556
Platinum Member
You could drill the pin on one end opposite the grease fitting and just use one bolt to constrain it to the bucket. That has drawbacks, but way simpler.
texasranger556
Platinum Member
Yes, that is one of the drawbacks!
dfkrug
Super Member
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- 05 Kioti CK30HST w/ Prairie Dog backhoe, XN08 mini-X
I don't have a picture in my mind of the square holes milled in for retaining pins, but....
I don't think you can reliably grease a shared pin from a single point. Greasing has always been a big challenge
for shared pins and therefore one of the big reasons I have always gone with separate thumb pivots. This is
also an issue with the shared boom/dipper pivot pins seen on some hoe attachments.
texasranger556
Platinum Member
Good point. Seems like the grease would flow in the groove you cut and then squirt out the space between the dipper and the bucket where the washers sit regardless of the square pin hole you're talking about. Nothing is there to force it into the thumb pivot, bucket bosses, or around the pin in the dipper bore. Grease guns can generate something like 10,000 psi...and of course grease like any fluid takes path of least resistance.
Yeah, I also came to realize that grease passing through a little groove won't make it past the gap between the dipper and the bucket. So last night I bored another hole on the other end of the pin and added another grease fitting there to grease just the thumb pivot on that side. Then I drilled a 1/16" hole on the other end to feed the other side of the thumb pivot. So when I grease the other side, some grease will feed the thumb pivot and then the rest of the grease will pass through the much-larger hole to the center and will feed the dipper. This weekend I'll put the bucket and thumb onto the dipper and grease it up to see whether this works. A tiny 1/16" grease passage concerns me that it will plug up in short order. Can always make it larger.
I'll still have to add a mechanical means of keeping the bucket boss tied to the pin. The boss on the bucket only has 3/8" of material to work with (2" boss with 1 1/4" pin), so there's not enough bonding surface there for any nutty JB Weld-kind of solution. Now I'm thinking of machining a larger collar that slips over the bucket boss with threaded holes that will enable putting in a bolt that passes through the milled slot in the bucket boss and grabs onto the pin. I like this strategy as it keeps the bucket as-is and it maintains the "form-factor" making it possible to use any other bucket with no modifications. I don't see that I'll ever change the bucket, but its always good to maintain the option.
I'll still have to add a mechanical means of keeping the bucket boss tied to the pin. The boss on the bucket only has 3/8" of material to work with (2" boss with 1 1/4" pin), so there's not enough bonding surface there for any nutty JB Weld-kind of solution. Now I'm thinking of machining a larger collar that slips over the bucket boss with threaded holes that will enable putting in a bolt that passes through the milled slot in the bucket boss and grabs onto the pin. I like this strategy as it keeps the bucket as-is and it maintains the "form-factor" making it possible to use any other bucket with no modifications. I don't see that I'll ever change the bucket, but its always good to maintain the option.
When JD fabricates the bucket, I think they use a mill to cut a slot in the boss BEFORE it's welded onto the bucket. That creates a square hole. Much easier than trying to drill a hole after the boss is welded on. You can see it here if you look closely.
Edit: added pic.
