Broken swing bearing bolts. Suggestions?

[pp13bnos]

I was servicing my new to me ex120-5 today, and noticed that I had 5 bolts missing from where the turntable connects to the upper structure. So I cleaned them out as best I could. Hoping that they had just vibrated loose..but we all know that never happens. They all broke off at the threads, probably about 2 inches up and into the holes. I was thinking that the best way to attack this problem was use a angle drill, and either using a easy out or taping the broken off bolt, then double nutting it, and hoping it backs out. I was just praying I wasn't going to have to split the excavator in half. Please tell me this won't be necessary. If anyone else has an idea of how to get them out, I'd love to hear it.

Also, this makes me wonder whats caused this issue in the first place? Thanks, CJ

 

[excavator]

Of the top of my head I don't remember which ones but not all the holes in the swing bearing have bolts in them. Are the missing bolts located on the right side of the upper structure, under the fuel tank area?

 

[alco]

Generally, if you have broken bolts on the swing bearing, the bearing is shot.

 

[uffex]

This was not uncommon with a certain excavator range I had experience with in the 80s, the method you suggest is that used then however we made a centralising guide to go into the hole. In those days going to the root cause was not good news, sometimes the bearing bed had become distorted or cracked part of the way round. After repair we replaced all the bolts since some had clearly stretched. I hope this helps you.

 

[uffex]

This was not uncommon with a certain excavator range I had experience with in the 80s, the method you suggest is that used then however we made a centralising guide to go into the hole. In those days going to the root cause was not good news, sometimes the bearing bed had become distorted or cracked part of the way round. After repair we replaced all the bolts since some had clearly stretched. I hope this helps you.

 

[excavator]

I worked on a Deere 120 this morning and I was wrong on my first post, the "missing" bolts are on the left side, under the cab and around towards the rear. They're not all next to each other, they are spaced out a bit. The Deere/Hitachi parts manual lists 30 bolts from the swing gear to the main frame. I don't know why they do this but that's the way they're built.

 

[wornout wrench]

I have done many broken swing bearing bolts and none of them have been any fun to do at all.
Here is what I do.
Have a machine shop build a insert with about a 1/4 inch hole dead center, get it so it just fits into the bearing and have a lip left on it that will keep it flat against the bottom of the bearing and it fits up just about the full depth of the bearing.
Using a angle drill, I use a 1/4" CP air drill, drill a centered hole right through the broken bolt. Make sure that you get it centered, really important! and go all the way through. Make sure you have a few spare drill bitts and they are good and sharp.
Once you get the pilot hole through then you can get it to the size you need for an easy out.
I like the Snapon ones with the left hand flutes on them
Drill the hole out as big as you can to get the biggest easyout in.
Go at it and make sure that you don't break the easy out off, that is a whole different story.

The other thing that I do is to change out the bolts on both sides of the broken ones because the ones left in are possibly stressed.

Broken bolts are a sign of something bad happening. Have a really good look, check the frame and the deck for cracks. If you can't find any cracks chances are the mounting surfaces are warped.

I have not done anything this small, normally I'm on 300 and 400 size machines. When we change out a swing bearing we measure the mount surface and not very often we don't have to have it machined, but then the machines that I work on are usually abused

Good luck

 

[pp13bnos]

Excavator, you just made my day! After reading your post, I decided to go out and count how many bolts where stuck in the machine. Turns out I have 30. And like you said, they are all under the cabish, and a little to the rear. I was seriously in a crappy mood all day thinking about how much of a PITA this was going to be, or how much I was looking at spending. I'm not sure why Hitachi/Deere did that, but usually when I see an empty hole like that it makes me little nervous. Thanks guys for the input.

 

[excavator]

You're not the first one this has happened to. Glad we could help.

 

[pp13bnos]

Thats a great idea wornout. If I ever do break some bolts this is exactly what I'll do. That will be a good excuse for me to convince my wife to let me get a lathe.

 

[alco]

We always put the largest diameter pipe we could fit in the hole, ran a new welding rod up inside the pipe, and welded it to the broken bolt, and used a pipe wrench to turn it out.

Unless it was a worn out old POS, then we cut bolts of the same size so there was about an inch of shank sticking out. We'd slip them in the holes, tack weld the back side so you couldn't see it, and send 'em to Ritchie Brothers.

I know, I know, it's beyond shady, but it's what the owner wanted.

 

[wornout wrench]

Welding them out is a great way to remove broken bolts. I have used it many times.

I never included it in this post because it takes a certain amount of finess to make it work right.

I have had to go to machines where someone has tried to weld them out with a pipe and MISSED, then you have a mess on your hands.

If you are going to try it use a piece of heavy wall pipe.
Take your time and let it cool before you try to wrench it out.
One of the things about doing it this way is that you get some heat into the bolt, if you let it cool down all the way it can make the bolt come out easier.

Like I said. don't miss. If you hit the threads or get a blob of splatter on them, you can open up a whole new can of hurt trying to get the bolt past it

Alco. Been there done that. Not proud of it either