What's the easiest way to remove plug welds?

[treemuncher]

I'm currently trying to remove a patch plate installed on my Lamtrac prior to my purchase of the machine. The machine developed cracks above the lift cylinders where the machine was not designed heavy enough for the punishment it takes in. I've been plasma gouging out the perimeter welds but have at least 8 plug welds @ about 1" diameter each to deal with in order to remove this plate. Patch plate looks to be 3/16" or 1/4". White paint outlines the cracks in the patch plate. My previous crack patch next to the left cab mount (primer brown paint area) with 7018 is still holding strong after about a year of use.


I'm looking for more knowledgeable welders that have to deal with this type of stuff on a daily basis. You experience may teach me and others a better way to approach this kind of situation.



I was fortunate enough to find a large annular cutter in my milling bits that fit into my mag drill. I drilled out beyond the circumference of the plug welds with it until I was nearly through the patch plate. Chisels and a railroad pry bar got most of the plate off, leaving the plugs behind for the plasma and a grinder wheel. I'm not sure this is the fastest or easiest method but I was making progress prior to shutting down for the evening.


After I get the old patch plate off, grind out & weld the cracks, I will install a larger 1/2" thick A36 plate to stiffen the entire front structure. The cab mounts are causing the ends of the front face to droop down so I will install a plate that measures the full width of the front. I will lay it in with some Washington Alloy Superflow 71tm mig wire if it's not windy when I go to weld. Otherwise 7018 if I have to deal with windy conditions. All weld areas will be pre-heated to minimize moisture.

Remember Newton's Law of Motion #3 : Newton's Third Law of Motion states that for every action, there is an equal and opposite reaction. This machine dishes out one hell of a beating on a daily basis therefore it takes in the same amount of energy. It's amazing that it stays together as well as it does. 20",30",40" and larger trees eaten daily. Sometimes stumps too.

 

[John C.]

The best I've used was a carbon arc. It's like cutting with a sharp knife.

 

[treemuncher]

The best I've used was a carbon arc. It's like cutting with a sharp knife.

Yes, I've used my Air-Arc many times over. I find it precise like an X-acto knife for chasing out small welds and the lengths of cracks. Those are especially useful in difficult to access locations. They are finicky bastards to keep a consistent cutting action, exceptionally loud and really get your hands hot.

These days, I rarely hook up the Air-Arc and prefer the Hypertherm plasma torch for gouging work that is not difficult to access. There is less noise, more precise control of the depth of cut with the adjustable amperage & air flow rates, and I don't think that the spark discharge is as bad with the plasma. I find the plasma torch more like a large paring knife or boning knife that lets me take off material faster and in precise layers when removing overlapping pieces like I have on this repair. After my session with the mag drill, I likely had 50% of the plate removed prior to quitting last night. Maybe I had 45 minutes total gouging time, if that much, to remove close to 36" of welded edge.

I did take out one of the plug welds with the plasma torch but it was not precise and took a fair amount of effort to avoid gouging the machine's metal surface. So far, the annular cutter was the best choice to free up the joke of a patch plate. I'll post more progress later today.

 

[digger doug]

Having only applied plug welds, you bring up a very good question, and looks
like your method is working well.
Mag drill out what you can, and plasma/air arc the rest.

 

[John C.]

I do like the idea of the drill and annular cutter. I looks very clean and for precision work I believe it would be the better plan.

The issues I have with it is that you need the mag drill and the cutter plus the time it would take for set up and the actual cutting. The other issue is that the surface you are working on would have to be flat and generally horizontal. The last part is the time it would take for set up and cutting. The air arc would be much faster.

 

[1693TA]

I've used air-arc, plasma, and annular cutters a lot. Small plugs are always taken out with annular cutters if I have the right tooling. Plasma if new, or very clean steel, and air-arc if crusty salvage type steel. They each have their places.

 

[skyking1]

You had me at mag drill.

 

[treemuncher]

The issues I have with it is that you need the mag drill and the cutter plus the time it would take for set up and the actual cutting. The other issue is that the surface you are working on would have to be flat and generally horizontal. The last part is the time it would take for set up and cutting. The air arc would be much faster.

Looking back, the drill was fast and more precise so as not to damage the original plate at the bottom. This system worked really well for me. Set up for the mag drill was installing the cutter, tightening 2 screws to affix the cutter , filling the oil cup, plug in the electric cord, set over where I wanted to bore the hole, flip the mag switch and then the drill switch. After that, each set up was no more than locate over the hole, flip the mag switch and then start drilling. I doubt I had 2-4 minutes per hole with the 1-3/16 cutter that I used. Maybe 20-25 minutes using the drill which was certainly more precise than using the plasma to cut all of the way down to the original plate. Best of all, no damage to original surface. Maybe 1-1.5 minutes to clean each remaining plugs off of the original plate.

Here you can see the last piece of the patch plate being removed. I did have to touch up 2 of the holes that I did not originally drill down deep enough so that the pry bar could removed the plate easily.


The eight remaining plugs took about a minute each to erase without touching the base plate with the exception of the one that I plasma cut around. That one took over 2 minutes to clean off as the edge surface did not get lifted. Here you can see the first 4 gone with just plasma torching.


All cracks that I could find were gouged out and/or ground out. I find it hard to believe that whoever installed the patch plate could not be bothered to repair a single crack prior to adding the patch for reinforcement. Lots of their welds were also very porous.


I managed to get all of the cracks filled in via stick welding due to the occasional breezes. I'll start cutting my 1/2" patch plate tomorrow AM. The mag drill will be busy making plug holes tomorrow to prepare for the install.


At this point, I'm glad I thought about my mag drill. Maybe it was slower than some other methods but it was very precise and no damage was done to the base surface. Once I got the plasma torch dialed in right, I was easily able to see and cut off just the top plate without adding a scar the the base. I'm really liking the gouging feature on the Hypertherm.

Thanks for everyone's input on this subject. Maybe these shared methods and ideas can help someone else later on.

 

[skyking1]

the mag drill worked great for removing them AND adding them. It's on my wish list, I have used them plenty but not my own.

 

[treemuncher]

I bought the mag drill on Ebay a few years ago when I added a lift axle to my truck. That and a set of annular cutter bits. It's a cheap Chinese unit but for what little I need one, it was a great investment at a bargain price. If it sticks, it drills! You would be surprised how fast those cutters rip through steel.

 

[materthegreater]

This is on my wish list

https://mag-tools.com/collections/drills/products/magswitch-magdrill-disruptor-30-8100920

 

[skyking1]

Funny story that I probably told before, my carpenter friend was working up on a bridge job out on the Olympic peninsula, and the new apprentice decided that it would be nice to not listen to those rattly generator noises while they had lunch. He turned it off and some number of greater than one mag drills dropped into the river. Oops.

 

[treemuncher]

After more mag drill usage during the day, I'm thoroughly impressed with my el-cheapo unit. I looked up what I purchased and it is a 1680W unit that I paid $270 for in 2019 via Ebay. It's not priced like the high end drills but it works great for my needs. I was busting holes in 1/2" plate today @ 1.25" diameter in 45 seconds or less. I was left with a large brillo pad of long chips at the end of each hole. I cut out the old plug welds and about 21 holes in the new plate with about 6 oz of cutting oil used in the drip feeder for everything so far. Best of all, no twisted wrists and all holes are perfect.

These are the chips around the cutter from a single hole.

I liked this thing so well at the end of the day that I went ahead and ordered more annular cutters and a jacobs chuck adapter for general bit usage. It's a major time saver and a much safer method of cutting holes when a mounting surface is available. Set up is much faster than using the vertical mill. All in all it is a major win in the tooling department for my needs.

After some more grinding tomorrow AM, this new patch plate should be ready for installation. The larger holes are the plug weld holes and the smaller ones are for the cab mounts. New plate is 1/2" steel and covers full width of the front.

 

[DB2]

Like the drip oiler. Going to check into one for our use.
Well thought out repair.

 

[treemuncher]

Over the past couple of days I finished welding in the new repair plate. My new repair is 1/2" thick and spans the full width of the front. It's roughly twice as thick as the original patch. All original surface cracks where chased out with a plasma torch, grinding wheel and/or die grinder and then buffed down flush to grade prior to laying in the repair plate. (as seen in post #8) I cut in plenty of plugs for better adhesion of the repair plate. Initially, the plate was set in with pressure to lift the outer edges of the machine where the cab mounts had caused excessive drooping over the past couple of years. The leading edge is no longer drooping on either side. Due to windy conditions, the patch was stitch welded with 7018 rods on initial set in.


Late in the evening, after the winds calmed, I was able to seal in a full perimeter weld and finish up the plug welds with the MIG. Often, I would normally just stich weld something like this to allow a little more flexibility but I want this bulletproof and weatherproof so that I don't ever have to fool with it again.


Patch plate painted up with cab mounts installed. I tried to cheat and just use the marks from the cab mounts rather than carefully measure everything. That came back to bite my behind as the cab mounts were too close as drilled. I had to bring out the mag drill to widen the mounting holes about 1/4" per side. Nothing but a waste of time just because I tried to cheat on layout time. Oh, and I can't wait for the ordered Jacobs chuck and Weldon adapter to arrive so that I can drill with conventional drill bits. The small holes were all drilled by hand and that really sucked compared to the safety and speed of the mag drill. No busted wrists or bits but a slow, difficult bore just the same using a conventional drill.


I'm down to the last bits of re-attaching the cab and associated hardware from the repair. Electrical, coolant, refrigerant and other lines had to be removed to allow cab removal. Thankfully, I had an extra set of eyes to help me line up everything and not crush any of the delicate components on cab installation. She wanted to see my view from the cab - no, neither of us trusts her enough to do a precision lift.


I also had to add riser blocks to the rear cab mounts - that's where the DRO on the vertical mill makes layout and precision drilled holes so much faster on these projects. Measure, dial it in, drill it, install it - done. After I get the AC recharged and finish zip tying the bits & pieces as required, I need to drop some belly covers and do a full rinse out. I'm hoping to be back to work with this thing this coming week. Seems like I've been repairing forever, again.

Between broken main lift table bushing holders, injector related problems, main frame crack repairs, grease system repairs and a few other odds and ends, I've lost nearly a month's work time. It could be worse if I was unable to tackle all of it by myself. I doubt that dealer repairs would have been as thorough as what I do, if I could find anyone to do what I needed done.

 

[materthegreater]

Very impressive work!

 

[Welder Dave]

Late to this discussion. Mag drills are great when you can use them. Instead of an oiler you can use a lube stick that's like a wax you rub on the annular cutters. It leaves less of a mess. If you're only doing a few holes you don't always need lubricant.
Gouging is great for removing steel on top of other steel you don't want to damage. The trick is to not turn the amps up super high where you have less control of how deep you're gouging. A lot of welders just crank the machine to the max. The other thing is to be in a good position to see the bottom of the gouge. This is usually easiest when looking behind the cut so the arc isn't restricting your view. It's a little different than welding where you're watching what the puddle is doing. Did a fair amount of gouging checker plate off of skids so heavy base plates for vessels could be welded directly to the beams of the skid. Took some practice but after a while it became pretty easy to almost surgically remove the checker plate without the slightest mark on the beams underneath.

 

[ThatGuysFarm]

Lots of ways to get the job done and it looks like you did a great job. If the back side was clear and accessible, I would have torched out the plugs and then made sure the new plug hole were in a slightly different location. Then plug welded inside and out. Annular cutters are great but I have had problems cutting near welds and wearing bits out quicker then I would like.