D6B (other models also) Lift Cylinder Pivot Easy Repair...

When Caterpillar introduced the D6B one of the features was the new style hydraulic blade lift cylinder mounting (pivot). Caterpillar doesn’t always get it right on the first try and these D6B pivots are an example that. The bearings for the pivot ride directly on the cylinders, there is no wear bushing to protect the cylinder. I don’t know if the later model D6Bs (The D6B was produced until 1967) had wear bushings fitted but when the D6C and the D7E were introduced in 1963 both had wear bushings.
I went to my local machine service McMahan Welding Service, Ltd to ask the shop foreman Kenneth for advice about the repair. I have relied on Kenneth’s advice for over 35 years and he came through for me again. We discussed several options as Kenneth looked at the photo of the worn pivot he had an idea for the solution. Kenneth told me about a bit called a core-cutter that when installed in a large drill press could mill the cylinder pivots to a smaller diameter and a wear bushing could be fabricated to fit the new bearings. The core-cutter bits are unique and expensive and I was fortunate that McMahan Welding had a large enough bit for this job. The new wear bushings were hardened after they were machined.
This idea worked great, there was no need to even disassemble the cylinders. I had intended to post photos of the machining operation, unfortunately I was not able to be there when it was done. The photos I took of the core-cutter bit were too blurred to use. I was so disappointed by the lack of photos that I didn’t post this for over a year. I finally decided that this post might have enough info to help someone.
Craig

Photo 1: The photo ops were jinxed from the start, a helper greased the pivots after being told not to grease them.
Photo 2: Picking up the repaired cylinders
Photo 3: Close up.
Photo 4: Installed on tractor.

[attachment=43884]pivot 1.jpg[/attachment] [attachment=43885]pivot 2.jpg[/attachment] [attachment=43886]pivot 3.jpg[/attachment] [attachment=43887]pivot 4.jpg[/attachment]

Very nice!

There are standard races available for shafts supported by straight roller bearings that maybe could be used instead of making them. Already hardened and precision ground......just have to pick one that would allow you to clean up the trunions with the cutter. Might not be available in the right sizes though.

Our local shop is well into the 3rd generation of the family. The original shop had a sign that said "We can fix anything but a broken heart and the break of day" Its probably stuck up in the new place somewhere I haven't spotted it yet.

By core-cutter, do you mean like the Milwaukee Steel Hawg Cutters, 2" cutting depth limit.
Like one of these??. They do produce a clean cut with carbide teeth.

Looks like the Milwaukee Steel bit would also work. The bit that was used is a more complicated design. I asked Kenneth if I could take pictures of the bit and he walked all the way to the far corner of the large shop to get it for me even though he was busy at the time. I tried to hurry as to not take up too much time and I didn't take the time to proof the shots and of course all of them were too blurry to use. I have been reluctant to ask for another try.
Old Magnet I'm not stupidstitious but this post has been a pain. I tried to post it several times yesterday and it would tell me I was not logged in. I tried again this morning and it took 2 tries, I was about to give up!
Craig

Hi Team,
not as good as the now available core drills to remove metal quickly and then finish the trunions accurately to size on a milling machine with an adjustable boring head and suitable cutter--was slow but got the job done when we used the boring head only.
We usually resized the trunion--if not worn too much-- and then fitted the later stock sleeve bearing--if worn too much we fitted a bespoke sleeve and then the stock sleeve bearing over that to keep it standard for the next time.
Combining the two tools would expedite the job greatly.
Cheers,
Eddie B.