Excavator Bucket Repair - Cracked Cutting Edge.

[Silverado]

Today at work my father pointed out a crack on the cutting edge of our 24" Kubota KX121-3 Bucket. Not sure how it happened but it was most likely me ive been in that machine quite a bit in the past two weeks.

In any event the crack needs to be repaired tomorrow - the machine works 6 days a week and running it with a split edge is not acceptable.

Here is what i am thinking --
- grind out both sides of the crack about 1/4" to a V so they just barely meet in the middle.
fill with 2 or 3 passes of 7018...

Are there any special tips or tricks for making sure this is a permanent repair?

- Is there a point to even trying to drill out the end in a 1/2 inch thick peice of cutting edge.

- I could also TIG weld it but I dont know what filler would be best and all i have is er70s2 and er70s4... I would love to know if there is anything out there for future reference tho.

Pics of the damage below...





And heres the machine and my rig...

[JOKER]

Grind a double V groove, extending an inch or so past the end of the crack. Put a root in one side, get full pen., grind into the root from the other side, fill that side, then the other side.

Toss sand or a welding blanket on it to let it cool slowly. 8018 or 9018 would work the best in a pinch. Eagle 823 Super will match that bucket a little better.

To do a "permanent" fix, it will be much more involved. Stop using your bucket as a jack hammer.

Best of luck.

[Stick-man]

Make sure to post pics of the finished repair. Oh, and it looks like you've got way too much tongue weight!

[killdozerd11]

Easy fix like joker said grind or gouge out the crack on both sides go beyond the end of it and 7018 will work just fine use the higher tensile if you got if not no biggie

That bucket material isn't that thick so pre / post heat is not necessary

That is stress cracking that comes from prying with the teeth and is completely normal wear and tear on backhoes and excavators ...i run them ...i brake them ..i fix them ...all a part of being an owner operator

[Bruce Avison]

Are you able to drill out the ends of the crack, and V past it? Should hopefully stop it from recurring/spreading. Can you get rod for hardened material (not just hard surface rod)?
Bruce

[Silverado]

Here it is, i ground the crack out 1/4" on each side, ran a hot root, ground the opposite side, then ran 3 passes on each side including the cap. I tried to do a basket weave type cap but i have not stick welded in a couple of months so the cap did not come out exactly how i pictured it.









Stick Man -- The truck looks like it has too much tongue weight because the torsion bars are cranked to level the truck out a little bit... i have been meaning to back them off for a while but its one of those things i never seem to get around to.

JOKER - The sad thing is we have access to an atlas copco variable speed hammer for that machine.

[killdozerd11]

And the other side ?

[Silverado]

? That is both sides. First pic is the bottom, second pic is the top.

[killdozerd11]

Sorry didn't pay attention

Having hydraulic issues with my kubota this morning

[dave powelson]

Apparently from your pictures, you didn't bother to wrap over the very front
of the crack where it initiated?

[Silverado]

Originally Posted by dave powelson

Apparently from your pictures, you didn't bother to wrap over the very front
of the crack where it initiated?

I did on the initial pass - theese pictures do not really show it.

[JOKER]

I am just giving you a hard time.You can most likely operate that hoe better than I. That should hold up for quite a while, under normal abuse. For future reference, multipass stringers will provide a tougher weld. This topic has been (and to this day still is) the start to a long argument among welders, because it is splitting hairs at some level. However, from past experience, each sequential bead will relax the previous one. Nothing wrong with the weave though if that is what you prefer.

Joker

[danielw]

This is where you should use a run off plate so the weld doesn't start or end at the lip.Also,stringers would be better here to impart less stress on the material.

[Silverado]

How exactly would I use a run off plate?

And thanks for the notes on stringers! i will definately keep that in mind, i initially had stringers then i covered them up with that weave -- as i said i dont think that weave is exactly beautiful but i wanted to give it a shot.

[Silverado]

About 18 months ago I made a duckbill attachment for this machine -- it slips over the teeth and is held on to the bucket with a turnbucle -- the cutting edge is 1/4" wider than the chain on each side so it does not make a mess when digging.

The duckbill is great - when trenching, digging, grading, loading (it lets you get a little bit more material in the small 24" bcuket.. we use it every day.

This extends the teeth and i am sure multiplies the forces when acting on the shanks when digging (especially because it is like a dirt-sail) - for a second i thought it was the culprit behind the crack - but the pockets do not slip over the shank that had the crack against it.

Anyways pictures below...







I would recommend making one to anyone on here that has a backhoe/excavator. I also made one for our CAT 314 excavator and that is used frequently as well.

[Gerry1964]

Originally Posted by Silverado

About 18 months ago I made a duckbill attachment for this machine -- it slips over the teeth and is held on to the bucket with a turnbucle -- the cutting edge is 1/4" wider than the chain on each side so it does not make a mess when digging.

The duckbill is great - when trenching, digging, grading, loading (it lets you get a little bit more material in the small 24" bcuket.. we use it every day.

This extends the teeth and i am sure multiplies the forces when acting on the shanks when digging (especially because it is like a dirt-sail) - for a second i thought it was the culprit behind the crack - but the pockets do not slip over the shank that had the crack against it.

Anyways pictures below...







I would recommend making one to anyone on here that has a backhoe/excavator. I also made one for our CAT 314 excavator and that is used frequently as well.

Thats a great idea, , and very well made

[daddy]

That thing is a good idea, I have used one. It is likely the cause of the crack. Should attach to every tooth to distribute the extra force as evenly as possible.

[danielw]

You would tack a plate(3/8or1/2')onto the edge of the lip.You then start your weld an inch or so away from the lip and by the time you've reached the lip the rod has burnt in nicely.Not cold and no porosity from starting.You then cut the plate off and smooth off the lip so there are no starting points for cracks.Hope that makes sense.

[killdozerd11]

I'm lost here ? duck bill ? a chain ? huh

[DSW]

Originally Posted by killdozerd11

I'm lost here ? duck bill ? a chain ? huh

It's a goofy way to attach a straight edge to a toothed bucket.

The one we had on our old 555 Ford backhoe on the 3' bucket, we welded the teeth right to the straight edge, with the exception of the outer teeth that were splayed outwards. You simply drove out the tooth pins and knocked off the teeth and straight edge as one unit. No need for the goofy chain set up. It's been about 6-8 years since we had that machine, but I want to say we had the straightedge mounted on top of the teeth, not underneath. That way when you dug, all the teeth, not just the ones mounting the straight edge, took the load.

My guess the way you have that rigged, the floor of the bucket is flexing between the fixed teeth and the ones that aren't doing anything. That caused the crack. If you flipped the straight edge over you'd eliminate the flex since the other teeth would help with the load when you dig.


I loved the straight edge for digging as it helped reduce the amount of shoveling I had to do to clean the trench between the tooth marks and made grading with the bucket a breeze.

[Silverado]

The only thing that confuses me is that the bucket was cracked alongside a shank that does not carry a loaded tooth when the duckbill is attached.

DSW - i may add support to the other teeth to more evenly distribute the load... We had a CAT 312 a few years back with an edge welded directly to the teeth as you described (that was great because changing teeth on that machine was easy), on the newer CAT machines we have now (2008) the teeth actually twist on to the shank before you pin them so welding right to some old is not an option. Also on the Kubota the pins are 1 time use and a nightmare to get out.... the chain may be goofy but it is very effective and we can take the bill on/off in about a minute. And it never interferes with anything... Bolt on edges that grab or go through the sides of the bucket can be a pain in the A** as well.

[DSW]

The tooth may not be taking a load, but I bet the floor of the bucket is flexing between the two supporting teeth. The thick to thin area of the unsupported tooth creates an area where these stresses collect and you end up with a fatigue crack or there was a weak point that allowed the crack to start.

When you push down on the tooth in the middle, it will cause the steel on either side to want to go up in the opposite direction. The side walls and teeth on the outside edges will cause it to bend back down again. you may not see the floor flex, but I bet it is from the way I see this built. If you ever saw a beam distortion, diagram for a multi supported beam, you'd clearly see that the beam bends up on either side of the support even though there is a load pushing it the other way. That's pretty much what you have here.


As far as the pins, I don't know what Kubota uses. We used to use roll pins to keep the teeth on with the straight edge. We'd get a few that would shear on occasion, but most times unless you were trying to lift with the edge, they held up fine and we used them over and over. The teeth looked very similar to what I see in the picts. We rented a few excavators with the twist teeth. Jury still out on those. Never got enough use to have a say one way or the other. I can see adding a straight edge would be a PITA. Probably change out the shanks if that was the case. I did hate the rubber filled pins that were stock on the original 18" bucket for the Ford. PITA since they went in sideways and if you tried to drift them out with a punch that was too small you'd F up the rubber between the steel inserts.

[killdozerd11]

We bent a piece of steel for a punch to do the inside tooth pins and shape it on the end to a oval shape so it hits the pin straight so it does not tear up the rubber in the center pins