JD 590D Excavator Swing Ring Bolts ?

[Cat 236]

My 1989 590D has the row of bolts around the swing ring of which there are 36 of them. There are 6 Bolts broken off and fallen out in this order, two broken, one still ok ,then 2 more broken, one still ok, then 2 broken. Would anyone have any ideas why they are broken off. All the others are tight. Should I replace them or just run it and keep an eye on the others for any loosness. I have made a preliminary attempt to drill and easy out but soon gave up as it is a tough time getting centered and to drill upside down in that narrow area. Thanks, Cat 236

[Dwan Hall]

First go buy a set of "left handed drill bits" eather Mac or Snapon sells them. Then remove the broken bolts using these bits and if needed an easy out. Then replace all the remaining bolts. Don't take a chance as it could be life threatning. Make sure you use bolts of the same grade for replacment.
If you are not able to do the job your self then have it done.
Don't run it till there are replaced, as something had to cause them to brake. If they had just fallen out that would be another story.


Dwan

[Cat420]

Depending on the area, a torch might also work to get them out. I would definitely replace them as soon as possible.

[digger242j]

I hate to sound uninformed (but I've long since gotten used to it). What are "left handed drill bits", and why are they called for?

[Cat420]

Left handed drill bits spin counter-clockwise and I believe they turn the bolt out as they grab.

[Steve Frazier]

Your bolts could have loosened allowing movement of the ring. This movement could have broken the bolts. It's very similar to having a wheel come loose and break the wheel studs.

I'd either replace them or have them replaced before running it any more, you're inviting a catastrophic failure if you don't.

digger, Cat420 pretty much described the bits, they're designed to cut in a counter clockwise rotation. Often times the friction from cutting will spin a broken bolt out of its hole.

[digger242j]

I assumed they were to be used while spinning in the opposite direction. I admit I hadn't considered the possibility that by itself that would back the broken bolt out.

I can't see how they'd help with the problem of drilling in tight quarters though. Maybe a right angle drill, like plumbers and electricians use for drillimg through wall studs would fit better?

[Cat 236]

Thanks for the feedback on this. Today I took a very very close look at the Parts Book and discovered that there are 36 Bolts on the inside ring and 30 on the outside ring. So I carefully counted the bolts 4 times and guess what? There are 30 Bolts like it calls for but 36 bolt holes. Now the mystery is why did they leave 6 bolts out at the factory in that order. Any ideas out there. Thanks, Cat 236

[Dwan Hall]

They may have left them out just to make you wounder why they left them out.
The left handed drill bits are in fact a little shorter then ther right hand counterpart.
I have found that in over 75% of the time I use the when drilling they snag the broken bolt and cause it to back out saving a countless amount of time and bad words.
The last ones I got were $28 a set of 5.

anyway glad you found the problem and it is not a safty isue.