Need welding advice on thick metal

[rust buster]

I have to replace the weld-on shanks that the teeth attach to on my backhoe bucket. The bucket lip is 1" thick and the shanks are about that as well.
I have a miller 252 and want to find a way to use that without resorting to buying/borrowing a stick welder.

Can I do this and do it right? What size wire? I'm guessing I'll need to preheat to help? I've read that some people prefer using fluxcore wire for this? Can I get away with a standard 75/25 MIG gas mix?

Or am I better off renting a stick welder and using 7018 rods?

Getting the existing, worn out shanks off is another matter altogether.
Thanks!

 

[pepi]

The miller 252 is rated up 1/2" your material is twice the rated capacity. I think the second option is the right one for the job.

 

[rust buster]

That spec is only for a single pass, which I wouldn't want to do anyway.

 

[WhoWhatNow]

I am not an expert but I would think that for a nonstructural weld like this you could bevel and do multiple passes. Yes the machine is only rated for ½” but with multiple passes you can weld thicker. Flux core may make it easier since it will be hotter. 3-4 overlapping welds I think you would be OK. Just remember to manage the heat/warpage.

 

[rsanter]

I would do some bevel. Some preheat and then lay a weld bead into the bevel to attach the part.
Then slow the feed a little and lay a nice fat bead over the original one

Bob

 

[pepi]

Single pass or not the penetration needs the heat I think. Maybe cut a V in the surfaces and weld and fill. I've seen that done on 1/4" stuff for a welder that lacks grunt. They trim the V so that the two surfaces are 1/4" total at the V intersect, therefor welding 1/8 and muty pass.

 

[JCByrd24]

Yeah that rating is not a limit that says you can't weld thicker material. Seems to be a marketing thing applied to consumer MIG welders. I don't think stick welders come with a similar rating and if they did I'm not sure one you rent at your local place would be rated any higher than your 252. Amps are amps and I think you've got a machine that will handle the job. Your not talking about a 110v powered machine.

Pre-heat, crank the 252 and go to town. Keep your gas and use the big wire, not sure what it is on that machine. 0.035 maybe.

 

[rust buster]

Yeah that rating is not a limit that says you can't weld thicker material. Seems to be a marketing thing applied to consumer MIG welders. I don't think stick welders come with a similar rating and if they did I'm not sure one you rent at your local place would be rated any higher than your 252. Amps are amps and I think you've got a machine that will handle the job. Your not talking about a 110v powered machine.

Pre-heat, crank the 252 and go to town. Keep your gas and use the big wire, not sure what it is on that machine. 0.035 maybe.

Great, I'll give it a shot. I think I only have .030 wire on their now, but I think I can get up to .045. And final dumb question. I'll preheat with my O2 acetylene torch, but how hot do I need to get it for preheat?

 

[JCByrd24]

I don't believe it's that critical in this application. I'd blast the area for a minute and call it good. Maybe someone else has better info.

 

[Sheriff Roscoe]

Great, I'll give it a shot. I think I only have .030 wire on their now, but I think I can get up to .045. And final dumb question. I'll preheat with my O2 acetylene torch, but how hot do I need to get it for preheat?

The hotter the better I would think. Your welder will need all the help it can get.

 

[JimDon]

After your pre-heat, make sure you hit both (adjoining) surfaces with a wire brush or wire wheel and take off the mill scale that will have formed. The cleaner the better when you use gas.
Jim

 

[zkling]

I've done a number of them, not fun, but it's work. My first question is are they worn that bad that the entire shank needs to be replaced? Barring extreme cases of neglect or just abuse, typically the shank is built up on the outside then refitted to the tooth socket. Why are you going to replace all of the shanks?

You can do it with the setup you have but you may want to consider the cost of consumables used. After you get the old shanks off, which ***** BTW, and have a clean surface to work with you will want to but a beval on the permiter of the shank so when slide on it will form a V with the edge of the bucket. Then fill the V with weld till you have a nice fillet. Make sure you get a good burn in on each pass, not with just the underlying pass but with the bucket and shank.

Preheat is really going to help. IF you are doing a number of them, unless you just love spending money with the gas guys, just build a little fire in the bucket and let it smolder for a while till the entire bucket gets up to temp.

If you do use the 250 setup you have, just watch the duty cycle. You will be putting down quite a bit of metal and although you are not exactly maximizing your deposition rate with that setup or compared to stick welding it will work as is. Back to my weigh the costs comment above.

 

[rust buster]

The previous owner used the hoe for years without any teeth on the shanks so they are beyond worn...so much that they are worn down below where the hole is for the tooth pin. I don't think I have any other option than to replace them, but I am certainly open to suggestions. I can get a pic later today.

 

[crewchief888]

ive welded a LOT of shanks and cutting edges on over the my years at const eq dealers.

the only concern i would have with your machine is duty cycle.

.035 wire (or .045 if your machine can handle it) and mix gas

multiple passes, 2 would probably be enough

clean the paint off the new shanks before welding

 

[isr2kba]

How do you get the old shanks (or what's left of them) off? Plasma cut then grind?

Maybe if you did one at a time, you would not violate the duty cycle of the source.

 

[zkling]

The previous owner used the hoe for years without any teeth on the shanks so they are beyond worn...so much that they are worn down below where the hole is for the tooth pin. I don't think I have any other option than to replace them, but I am certainly open to suggestions. I can get a pic later today.

Awesome. BTDT.

How do you get the old shanks (or what's left of them) off? Plasma cut then grind?

Maybe if you did one at a time, you would not violate the duty cycle of the source.

I used a combination of a homemade air arc setup, oxy propane and a 4.5" grinder, chisel and grinder. You want to "cut" the weld at an angle to separate the pieces without actually cutting through the bucket. It's by far the worst part of the process IMHO. One tip, is to pressure wash the area so you can see what you are working with.

As for the duty cycle, the issue is with smaller wire as it limits how fast you can lay metal down. Even just welding the perimeter takes a good while.

I'd like to hear Crewchief's tips and tricks though. I've only done a handful of them (<10), so it would be nice to hear from someone that has had more experience with the process, especially in a pro setting.

 

[brianpgriset]

Get the right gas and you can probably do spray transfer with that machine. I'd think it would weld it up no problem.

 

[rsanter]

Tack the new part on where you want it
For heat you only need to get to a dull red or close to it color

Bob

 

[vaquero55]

I replaced two shanks on my JD backhoe a few years ago. Also used my Millermatic 252.
Gouge out the original weld with your O/A torch(gouge towards old shank, not bucket), grind out cut if needed and knock off the old shanks.
Clean up your old welds with a grinder, grind the paint off your new shanks, tack your shanks where you want them, and go to town with your 252.
I made a first pass in the bottom of the V, and then laid two passes on top of the first pass(either side). I used 0.45 wire and 75/25gas.
Have dug tons of rock and dirt with it since then, no sign of anything failing so far. Don't be scared, you will be fine.

Edit- I see no reason to go through the hassle of pre-heating anything. It's a backhoe bucket, not a life or death structural piece.

Hired man grinding cleaning up the old weld-


Ready for a new tooth and get to digging- I actually did this one with a stick welder, but not to long after we broke the other corner shank and welded it with the 252

 

[Outlawmws]

I replaced two shanks on my JD backhoe a few years ago. Also used my Millermatic 252.
Gouge out the original weld with your O/A torch(gouge towards old shank, not bucket), grind out cut if needed and knock off the old shanks.
Clean up your old welds with a grinder, grind the paint off your new shanks, tack your shanks where you want them, and go to town with your 252.
I made a first pass in the bottom of the V, and then laid two passes on top of the first pass(either side). I used 0.45 wire and 75/25gas.
Have dug tons of rock and dirt with it since then, no sign of anything failing so far. Don't be scared, you will be fine.

Edit- I see no reason to go through the hassle of pre-heating anything. It's a backhoe bucket, not a life or death structural piece.

SNIP

Because he's using a relatively speaking, light duty welder. He can easily get good penetration vs a cold weld, and have to redo the job when a tooth rips out...

Heck, I've preheated on some arc welding jobs.

 

[rust buster]

There's a lot of good info here, thank you!
I'll post up some pics and when I get to it and let you know how it went.
I'm looking forward to the welding but dreading the removal of the old shanks.

 

[JonnFX]

You could probably use a dual shield setup. It is amazing how hot you can weld with this. It is a special flux core type wire that still requires external gas shielding. A .045" wire is commonly used.

 

[-->]

You can take the old shanks off with a regular torch if you don't have a plasma. I'd use a wire wheel to clean up the new shanks and the bucket. Do multiple passes and you should be okay. If you're doing it outside make sure your gas doesn't blow away, Stick would be better. You don't need to bevel this.

 

[vaquero55]

Because he's using a relatively speaking, light duty welder. He can easily get good penetration vs a cold weld, and have to redo the job when a tooth rips out...

Heck, I've preheated on some arc welding jobs.

To each his own.
In my opinion, pre-heating this particular project is way, way overkill. If he is a good or better welder, he should never have an issue with his welds breaking in the future.

 

[sberry]

Thick sections need pre heat. There are better options but using what you have would work for a one off repair, would rather have 035 in a 252.