Well, that was anti-climactic...

[Toolslinger]

The left boom arm broke on my old 646 last winter... Today was the day I was going to get that apart and start getting it back to functional.

I set up everything for the war I saw coming...

Ratchet strapped the boom arm together, and limped it from my storage garage, down the street to my garage at my house. Fired right up, without complaint, strap held, and nothing eventful... Strange to begin with...

I got all the implements of destruction out and ready.
Grinder, with various wheels.
Saw-z-all
Big punches, little punches, 3' of 3/8 rod to drift the pin out all the way
Little hammer, big hammer, sledge hammer
Even a couple pullers, though I didn't see how they'd help.

Amazingly, all I had to do was grind the mushrooming off the roll pins. Punch them out with the little hammer.
I snaked off the broken end of the boom, and then thought I'd give the pin a good hit with the lead hammer.
Damn thing went in almost flush to the tower...
So, around the other side, and I drove it back in, checked the strap, and tapped it out of the good arm. After that it just slid out of the tower...

So far, that's the easiest thing I've ever taken apart on a little Case...

Pin is trash unfortunately. Bent a little on both ends, and worn where it passes through the tower. Odd that there isn't a way to secure the pin to the tower, since it is supposed to rotate at the back of the boom arm. I'll have to take a look at doing something there, though it did make it from '75, to winter of 2020... Suppose that would be ok again.

Didn't remember to bring my JIC fitting plugs, and caps home this weekend, so I'm going to order another set. That way I can pull the whole boom off for welding. No reason to start sparking up around a tank of gas, and oil, plus the greasy condition of some areas...

So... What have you used for replacement pins? I'm thinking a piece of hardened 4140 would do it nicely, but I'm open to suggestions...

So, now, with an entire afternoon free, it's time for a beer (or more)...

[Eugen]

Better this way than the other way. Rarely happens though, when , at least to me.

Isn't the downside of hardened pins that they wear out the arm?

[Toolslinger]

Yea, that's a possibility certainly. Nice if they were replaceable bushings, but I guess Case felt nobody was going to really wear out a steel bushing, with a 3/4" pin on a 1500# machine.

[Eugen]

I don't have real experience with this, but it makes sense that you'd rather replace pins than the whole arm, if the bushing is not replaceable. In the same time you don't want the pins to be too soft either. I'm thinking that Case must've chosen the hardness on the pins to be just below the hardness of the bushing. Safest to get OEM pins? I'd be surprised if one of the few Case parts vendors don't have them.

[Toolslinger]

At some point the other shoe is going to fall...

Once the caps and plugs came in, I pulled the hydraulic lines at the loader tower. No drips. That's a miracle... Hydraulic work, and no mess...

Stripped the lines, and bucket cylinder off the boom.

Pulled the bucket off.

That all went extremely smoothly.

So I tossed the boom in the truck, and took it to work once my steel came in. I also bought 6" of solid rod, and an aluminum 3/4" shaft coupler.
So I was able to get everything cleaned up for welding, then run the steel shaft through the good arm, over to the bad side. I clamped the copper on, and put the tail end of the boom on, and slid it all in place. The boom must be twisted just a little from the years of abuse. So, the tail piece was under a little tension, and sat right in the old crack lines nicely. I made sure the boom arms were spaced correctly. Turned up the metal glue gun, and got it all welded back together. No issue twisting the shaft assembly in there. So after that cooled, I pulled the shaft out, cut it to length, and did the cross drilling for the collars that hold the arms on when installed. Even had enough 4140 left to make a new pin for one of the lift cylinders, which had an incorrect piece in there.

I dropped it all off at my house, and that's where it sits now... I'm out of town for the weekend, so that should all go back together next week... If so, then it'll be on its way out here to the farm in a couple weeks. I have a number of projects for a hoe, and our bigger machine is so messed up, I don't know if I'll ever fix it... (MF202, with another Davis design product, and unfortunately, a rotary cylinder you can't get parts for any more...)

[Eugen]

You should buy lottery tickets! Hydraulic work with no oily mess?!

Definitely looks like you're on a roll there. Did you have to turn the 6" rod at all?

[Toolslinger]

No need for turning. I got rod that was +/- .002. I haven't checked to see where it falls in that range, but I figured I was pretty safe at having it work. The only reason it's cranky running through both bushings, is that the loader boom is a little tweaked. I suspect that is the reason it was rotating in the loader tower, rather than at the boom end. I'm going to see if I can get a shaft clamp inside the tower to hold it, and force it to rotate at the boom end where it gets grease.

[Eugen]

No need for turning. I got rod that was +/- .002. I haven't checked to see where it falls in that range, but I figured I was pretty safe at having it work. The only reason it's cranky running through both bushings, is that the loader boom is a little tweaked. I suspect that is the reason it was rotating in the loader tower, rather than at the boom end. I'm going to see if I can get a shaft clamp inside the tower to hold it, and force it to rotate at the boom end where it gets grease.

You definitely got access to quality stuff, if you get 6" steel rod with += .002 deviation. Show us a pic of what you're working on, sounds interesting!

[Toolslinger]

Guess the brain was going faster than the fingers....

That was 6" of 3/4" solid copper rod, to run through the bushing while welding. That's the +/- .002
The 4140 rod that is to be the actual pin is +0/-.003

So you got me wondering if I could even get 6" rod at +/-.002... Probably someplace, but McMaster only has it at +0/-.006 in the 4140... Guess it wouldn't matter if I was turning that down to 3/4"...

[Eugen]

Haha good one! You had me puzzled there for a bit. I was thinking what kind of monster you're working on there that has a 6" diameter rod!

I happen to have some 3/4 rod of unknown origin and put it on the lathe out of curiosity the other day, big time out of round.