Tips for welding hydraulic thumb mount to arm stick

[John V]

Hey, I'm adding a hydraulic thumb to my komatsu pc35mr-2. It's a main pin style thumb, but I need to weld the top mount for the hydraulic cylinder. Any tips or things I should know about welding onto the stick?
Thanks

 

[John V]

Here’s what the mount looks like

 

[materthegreater]

I'm surprised no one has responded to this yet. I've only done this a couple times so I'm no expert but this is what I've heard is important in welding on equipment.

Only run your weld beads along the length of the arm, never across. The mount is designed to accommodate this, since it has the long ears above and below the car cylinder mounting tabs.

Use 7018 rod, or dual shield wire, or equivalent. Start your beads 1-2" before the mount and run them 1-2" past the mount. Then grind these "tail ends" in a smooth taper down to the parent material. This should help reduce stress where the ends of the mount meet the arm.

Obviously make sure you grind all the metal clean where you will be welding. Make sure you use a welding machine powerful enough for the task. Don't use a 120v wire feed welder with solid wire. (although we all like to joke about doing it!).

 

[Coaldust]

I'm surprised no one has responded to this yet. I've only done this a couple times so I'm no expert but this is what I've heard is important in welding on equipment.

Only run your weld beads along the length of the arm, never across. The mount is designed to accommodate this, since it has the long ears above and below the car cylinder mounting tabs.

Use 7018 rod, or dual shield wire, or equivalent. Start your beads 1-2" before the mount and run them 1-2" past the mount. Then grind these "tail ends" in a smooth taper down to the parent material. This should help reduce stress where the ends of the mount meet the arm.

Obviously make sure you grind all the metal clean where you will be welding. Make sure you use a welding machine powerful enough for the task. Don't use a 120v wire feed welder with solid wire. (although we all like to joke about doing it!).

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Well
Done !

 

[John V]

I'm surprised no one has responded to this yet. I've only done this a couple times so I'm no expert but this is what I've heard is important in welding on equipment.

Only run your weld beads along the length of the arm, never across. The mount is designed to accommodate this, since it has the long ears above and below the car cylinder mounting tabs.

Use 7018 rod, or dual shield wire, or equivalent. Start your beads 1-2" before the mount and run them 1-2" past the mount. Then grind these "tail ends" in a smooth taper down to the parent material. This should help reduce stress where the ends of the mount meet the arm.

Obviously make sure you grind all the metal clean where you will be welding. Make sure you use a welding machine powerful enough for the task. Don't use a 120v wire feed welder with solid wire. (although we all like to joke about doing it!).

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View attachment 313714

Thanks for the thorough reply!

I have a 220v miller mig welder that's rated up to 3/8 in a single pass. I've never used the dual shield wire, only the solid wire. If I run the dual shield, do I also run C25 gas? How come using solid wire is bad?

Appreciate the tips!

 

[materthegreater]

Some dual shield wire can be used with C25, just make sure it can when you buy it. Others are made for C15, or 100% CO2. They won't give satisfactory results with C25. This is what I've been using: https://www.kiswelusa.com/product/k-71tm-e71t-1c-1m-0-035-in-dia-10lbs-2/

Solid wire isn't necessarily bad, but it's easy to get a nice looking weld with no penetration (obviously not a good thing if you don't want the thumb falling off when you're lifting something heavy). This was on a Tucker SnoCat. Never would have known there was anything wrong with the weld by looking at it.


Dual shield is a much hotter process and is much easier to get good penetration. That being said, it also runs a bit different than solid wire or gasless flux core, so you'll want to experiment with it on some scrap before welding on your excavator with it. The biggest thing I have found with it is that the weld area must be extremely clean. It won't weld through rust or paint without giving worm tracks or porosity.

 

[John V]

The wire you shared by Kiswel said it's recommended to use 100% CO2 or 80/20 Ar/CO2. Wondering if it would be fine to run C25. I don't do too much welding, so I'd rather not have multiple bottles around.

 

[materthegreater]

Oops, I guess I linked the wrong one. I bought it through Amazon and it was for C25. I'm sure there are other brands that work with C25 if the Kiswel isn't available or maybe they've changed the formulation to require 80/20.

 

[John V]

Oops, I guess I linked the wrong one. I bought it through Amazon and it was for C25. I'm sure there are other brands that work with C25 if the Kiswel isn't available or maybe they've changed the formulation to require 80/20.

this stuff?

 

[materthegreater]

Not sure, the spec sheet they have there doesn't say anything about gas at all. I've found Amazon's descriptions to be a bit lacking at times...

 

[materthegreater]

It might be worth buying a name brand wire to take the guesswork out of the picture. Do you have a local welding supply store?

 

[Shimmy1]

This was on a Tucker SnoCat. Never would have known there was anything wrong with the weld by looking at it.
View attachment 313767

Wow. Whoever welded that should have the stinger shoved up his pucker and the trigger pulled. Obviously wasn't prepped in the least, and no preheat.