Where can I source thumb-fitting instructions?
Welcome to HEF, priemy1 ! What brand and model machine will you be putting it on ? Are you interested in a manual thumb or one that is hydraulic ?
I have a CAT 305.5 D and a Hydraulic thumb. There weren't any instructions with the thumb so I will have to wing it.
The serial number of your 305 will be needed. You bought a thumb for the machine and need help installing it ??? Who is the manufacturer of the thumb ? Is it pin mounted on the bucket, or does it need to have brackets welded on the dipper ??? Is the backhoe plumbed for a thumb or, do you need help with that to ?? One picture is worth a thousand words.
Its a huge chore, especially if there is no hydraulics for it ready to go.
The 305.5 is a mini excavator. The thumb is locally Aus manufactured ( Aus buckets) and a weld on. The machine is plumbed for attachments. I just need to work out the right spot to fix it on the stick.
It's plumbed for an attachment.
Is this the one you have ??? If it is, are you asking how high above the bucket pin to mount it on the dipper ? I can't help you with that. Have you tried contacting whomever you bought it from ?? Here is a link to Aussie Buckets for anyone that can help you.
I believe that you want the lower edge of the main pin bushing of the thumb to be roughly 1” from the edge of the ears of the bucket/coupler when it is curled all the way in. Not 100% sure, it’s been a while since I installed one.
That's the one. Have sent them an email.
Thanks, Tags. That's what I needed to know.
You could use C clamps to hold it in different positions and see where it you want to mount it. When the thumb is retracted, it is important how close the bucket teeth get to it when the bucket is curled all the way in.
Wouldn't asking the manufacturer make more sense than asking a bunch of people who have never seen one and aren't there to see it ? Joe H
Clamping or temporarily tacking it in place could work. I think you'd want to fit the thumb so it aligns properly with the bucket when the bucket is straight out from the stick or slightly forward of that. You don't want the thumb going inside the bucket and you don't want the thumb 6in. past the bucket. There are probably mounting instructions on the internet if the manufacturer can't provide them.
Yes you will want to tack (with substantial tacks!) and make sure of fitment, travel, interference with bucket teeth, etc before final weld up You really need to get the instructions from the manufacturer for the installation. That should give you positioning instructions and weld procedure. For Cat typically you will not weld across the stick, they don’t like that. Cat can also supply the valving/fittings to install a small valve block upstream of the final aux valve block allowing the thumb to be shut off when stowed and another tool being run And MOST IMPORTANT! You will need to tee in a gauge and set the pressures on the aux circuit relief so that the thumb can be overcome and collapsed by the bucket and also so that when stalled out the thumb is not getting to much pressure. If you do not do this you can bend or snap the thumb cylinder rod. This valve on the smaller equipment is set manually with an Allen wrench and a regular wrench for the lock nut.
Yes, don't weld across the stick, only length wise and use 7018 or equivalent wire welded by someone with enough experience. You don't want it breaking or twisting.
Why ought it not be welded across the stick?
Have to keep the water out of there some how. I as well prefer it to be like a fish plate with 45 degree vee's, but then a bead that runs inline parallel to beam that strings off each corner is a good preventative measure after the non lengthwise bead. I always like full (for lack of a term) circle welds to keep water out, water will just start the rust process inside where the welds were made.
Thanks, gang.
Unfortunately, the manufacturer didn't include instructions but provides any amount of information over the phone. I would have preferred something in writing.
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.
It doesn't rust away, it splits when it freezes. My old Case had several. Joe H
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.
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.
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