Thumb Kubota BH75 Damaged by bolt-on Thumb

[MacPDaddy]

BTW, I am surprised that your dipper is made of 1/8" steel, as the B21 hoe
I used to have used 3/16" like my current hoe.

I was also pretty suprised how thin it was. I asked Roger if he could get a short cross section so I can get a picture of the original stock as well. He may, but no promises at this point as they may have sent out scrap already.

Actually it looked like the arm had a slight bend between the 2 bucket pins, I may assume that 1/8" may be slightly on the thin side for digging alone. During my visit to the dealer this past weekend, it did seem like the thickness in the hoes had been increased, maybe 3/16" is now used. I appreciate your input, pretty new to thumbs.

 

[dfkrug]

Actually it looked like the arm had a slight bend between the 2 bucket pins, I may assume that 1/8" may be slightly on the thin side for digging alone.

Your pix in post #6 above do seem to show some curvature in the dipper.
Amazing. To actually get some bending BETWEEN the pin holes in the dipper
is more amazing. Let this be a warning to anyone with a Kub BH75 not to
use a bolt-on thumb.

Your replacement dipper stick looks good.

 

[AKfish]

Somethin' to consider for everyone using a bolt-on thumb.. not only BH75 owners - IMO. And this forum is a great resource for all of us to benefit from the experience of one another.

Ol' Roger is a good hand - he done real good - the repair looks like OEM.

Looking at your pics; it appears that the thumb will only fit down low on the dipper - close to the pivot pin on the bucket. Or maybe that's just the way the pic looks..? If you could move the thumb up higher on the dipper; the compression forces from the bucket against the thumb would not be at such an abrupt angle to the dipper stick; I'd think.

The inside plate (between the side walls) on the dipperstick on my old JD 8A hoe was thin, too. The side walls were heavier plate (1/4") as I recall; but the inside plate was all bent up and rippled from rocks, trees, etc. being forced against it by the bucket during normal use.

When I welded the thumb on, I used 3/8" plate for the upper and lower pivot points on the thumb and that ended problems with rippling...

AKfish

 

[MacPDaddy]

Looking at your pics; it appears that the thumb will only fit down low on the dipper - close to the pivot pin on the bucket. Or maybe that's just the way the pic looks..? If you could move the thumb up higher on the dipper; the compression forces from the bucket against the thumb would not be at such an abrupt angle to the dipper stick; I'd think.
AKfish

Yes it will only fit low on the arm, you run into hitting the cylinder if you place it any higher.

 

[MacPDaddy]

I have the finished arm back tonight.
I also got a cross section of the original arm which I will post pictures of, it is 1/8" steel all the way around.
Tomorrow is paint day, I don't know if I'll get to install it. I'll take pictures and post them this weekend.
We did install thumb attachment locations, the thumb construction will happen later.

 

[MacPDaddy]

The arm is ready to paint.
The only Kubota parts are the 2 plates at the top, and the 3 pin sleeves.
Notice the installed thumb support and the third sleeve for the thumb mount.
We will design the thumb once we have it back together.

The craftsmanship that Roger put into his work always amazes me.

A slice of the original BH75 Kubota dipper arm shows the 1/8" steel construction.
In my opinion, this is a little light duty for the arm. I guess it works as long as you don't get too overzealous (or stupid as was my case).
As I said earlier, it looks like the arm had bent BETWEEN the 2 bucket pins, and I don't think that was the thumb's fault.

Unobstructed view of the factory Kubota BH75 dipper arm section.

Compare the old arm section to the new heavy duty arm.
Surprising that the overall weight increase was only about 20 lbs.

I'm really happy with the result, the 1/4 steel is visible on the end.
Roger duplicated every factory weld, even the sleeve welds visible here in the center of the end piece.

Primed....

and painted, ready to install tomorrow.

 

[irvingj]

Wow, that looks beautiful!! I'm also planning to add a thumb, probably Bro-Tek, to my M-F GC2310. Anyone out there have experience with this set-up? Does the 2310 have issues with the use of a thumb?

 

[MacPDaddy]

ALMOST DONE!!
The Thumb arrived today (Roger and I fit it last Friday so I know it's good).
The only thing left is to get it painted and installed.
The thumb is made of 1/2" thick Hardox 400 steel, the same material often used for buckets or dump truck beds on large equipment.
I am using Kubota Orange on the support strut and ROPS Grey on the thumb itself.

 

[radioman]

Very nice thumb. look forward when you have it all together and shined up.

 

[wushaw]

Cool