Welding to repair bores

I'm welding up the top swing mount on a backhoe and then hoping to bore the hole to size for the hard bushing. I've ground the bore 1/16"+ bigger than the bushing. There are some slight gouges in the bore from a spring steel bushing that turned a bit in the bore from being too loose. Should this be enough oversize so I don't pick up extra carbon from the turned bushing and also enough so that I'm not affected by the heat affected zone (HAZ) when finishing the hole to final size? I will be preheating till hot to the touch and planned to use 7018 for build up as I've read it is fairly common for stick welding bores. Is this a good plan of attack or would a rod like 7014 be easier to bore? I'm hoping to use a heavy drill press to bore the hole going very slow with very light cuts. Any expertise is appreciated.

have somebody do fire watch for you.

I doubt I'll be able to find someone. I can spray the area down with some water where hyd. oil has spilled or leaked. I read your recent post about a hyd. oil fire so will take necessary precautions and have a fire extinguisher in close proximity. Moving the machine forward a little will move it further away from spilled hyd. oil.

I have always used 7018 for everything back in the day, except some special alloy's I've welded. I used 6013 and 7014 alot when as a kid I got an AC welder, I didn't like that flux at all and seemed like it was very easy to get porosity from it. I may try it again now and see how well it works with DC. As far as machine ability, the 70 means about the same alloy content so they should both machine the same. Dirt is your friend with hydraulic oil fires, stories to tell.

Well I went out today to work on the bore. I clamped a piece of aluminum on the bottom but not sure if it made it easier or just made a mess at the bottom. I preheated it till it was hot to the touch and was using 3/32" 7018 to try and build a shelf. It's a good thing I pulled the machine forward. Even with good access around 3/4 of the bushing it was still quite a challenge to try and get an even weld all around. I must have used about 20 3/32" rods before I had enough of a shelf to burn 1/8". I only had 1 3/32" rod left so went up to 1/8". It was considerably faster but I had to move faster too. Thankfully I had good Blueshield Electrodes. Nicest burning 7018 in Canada. The nice thing about 7018 is if there is a little slag left it will come to the surface with the next pass when the piece is hot. You can actually leave the slag on when doing multi-pass welds and get a really smooth weld that looks almost like it was done in 1 pass. Not sure the same is true with 7014. It took longer to build up than I thought it would and was damn hot even with welding gloves on.

When I was doing it, it looked pretty rough but after I was finished and ground the top edge down a bit some of it looked pretty smooth and even. It really helped that I an old red face SA200 to do the welding. Very smooth arc, I couldn't snuff out the arc if I had wanted to. Trying to do this with a low end welder or buzz box would have been very frustrating. I filled in the enlarged slot Cat puts for the grease so I wouldn't have a potential trouble spot boring the hole to size. Hopefully I can drill it back out through the grease fitting hole. I can always use a carbide burr to make the grease area on the inside of the bore a little larger. The hardened bushing is turned down in the middle so there is a half circle kind of groove and 4 holes around it to grease the pin. I was going to get a plug wheel to fit on an angle grinder to grind the build up down and even out the high spots before trying a boring bar. I've read the surface of the weld can be a little harder than the rest of the weld but don't know if there's a difference. I know the puddle can pick up carbon if there was galling from a hard bushing or the part you're building up is higher carbon steel. I cleaned it pretty good and it was oversize before welding so I think I should be OK. It appears to just be mild steel. I am wondering if I need to fill a couple low spots if putting more weld on would cause hard spots? I would preheat it if need more build up. I'm also wondering if I need to try and anneal the weld to make it easier to machine? I've read you heat it up to about 1200 deg's. and then wrap it up or bury it in vermiculite, sand or something so it cools really slowly.

Nice to read a welding procedure done by a true professional.
You must be feeling a little better, Dave !

Years ago before I had a bore welder I too used 7018 for many of the same reasons cited. I still have the copper back up blocks used all those years ago to build a "ledge" upon at the bottom of the bore. Once welded, I usually welded a heavy plate to the king post for a mag drill to attach to and a friend in a machine shop would grind an end/shell mill for plunge cutting the bores to size. Slow going due to lack of absolute rigidity in setup, but not a lot of second time operations needed this way. More to it than that for piloting of course but this is the gist. Many times heat the post area after machining to expand the hole, and drop a frozen bushing into place allowing the parts to shrink, and grow to a press fit. Hone to size afterward.

Glad to read you are feeling up to such a task. On the road to recovery although slow. Never give up. As long as you keep the mind engaged, the body usually follows.

Keep it up.

I know nothing about welding Dave,but enough about earning enough coin to be able to pay for a good welder.
I’m just happy for you that you’re well enough to tackle the job now.
Keep up the good recovery sir

Tinkerer said:

Nice to read a welding procedure done by a true professional.
You must be feeling a little better, Dave !

Click to expand...

I didn't feel like I did the most professional job although this was the 1st bore I ever welded up. My welding is pretty rusty from what I used to be able to do but I could see better than when I did some welding last year. That's the most important and was a huge bonus. I'm sure my experience helped a lot when I couldn't always have the rod at the proper angle. I had to get it to fingernail (flux burns uneven) to keep the slag back on some spots where I had to use a straight on or even a push angle. I also had to do some of it the crash and burn style with only one hand holding the stinger. This is where the machine I was using made it possible. I could pretty much drag the rod, vary the arc length and run it at different angles without any fear of the arc snuffing out. If all I had was a low end welder would have been a nightmare. Hopefully I got enough buildup and the boring head I got can get the hole close to size. Need to very carefully set the drill press up square with the machine. I'm thinking of bolting some square tubing to the base and welding nuts on it for leveling screws. I think I can get it very close this way using a digital level.

I used to like Lincoln E-7018 rod, who knows now, I think it is all junk from other places. Yeah its nice to have a good stable welder the best I ever used was an old Lincoln Motor/ Generator unit I think it would go 400 Amps.
Bosses old ford service truck had a huge old miller that I had to occasionally flash to get it to work, special switch I installed made it faster. Don't know why it would lose residual magnetism, and don't even remember if there was an exciter or not.

A Miller is a 3 phase alternator with a rectifier to get DC current. I've never heard of a Miller needing to get flashed but have heard the slip rings can need to be cleaned up. I don't think Miller's need residual magnetism because they aren't a true DC generator. Lincoln 7018 isn't common in shops here. Most shops use Blueshield but some have gone to Esab OK55 made in Sweden because it's less expensive. I don't think the OK55 is available in the US or has limited supply. Esab Atom Arc 7018 is pretty good too. A good machine makes a huge difference on difficult or out of position welds.

Yeah don't remember, I do remember having to flash it to get it to work on occasion. It did generate AC, to use electric tools, I think only 10KW for such a large welder. Had no time to remove it from the truck to trouble shoot it. Too many other projects.

I think the welding part takes a bigger generator/alternator than the aux. power. Interesting though is how the air cooled machines like TB 325's and Lincoln 305's can have 11 and 12,000 watt AC generators in such a small package in addition to having a 300 amp welder. The AC generator can usually be used at the same time. I think on the Miller the AC and welding are completely independent of each other.

I have an old Hobart Brothers commutator based engine drive machine which I just cannot let go of citing the way it welds. Dave is very correct in these being the best there is generating DC current through commutation rather than rectification of AC. However, I also have another Hobart machine that is rectifier based for DC and it will match, and sometimes best it in performance. With me they both have their purpose. For a quick repair job in a field, the old machine goes as it's all inclusive except PPE and consumables. A larger job, or in this case, "welding up bores", I grab the newer machine as it has CV, as well as CC output. CV, (constant voltage) is required for wire, or mig welding, so the old machine only gets pressed into service for "stick' processes any longer which is a constant current requirement.

Mig would probably be easier to weld bores, especially building the initial shelf at the bottom. It might be harder to see past the nozzle though. I think a Mig weld is a little harder than 7018 so it won't machine quite as easily. I had an old Hobart 200 amp generator from the 40's. It was a DC generator on one end and a 10 HP 3 phase motor on the other end plus it had an extended shaft to couple to an engine, a Chrysler industrial in my case. It had a very nice arc. It was mounted on a trailer and was a big ugly looking thing but it welded great. A farmer who was a little bit familiar with welders bought it off me.

1940s WWII Era Troy,Ohio Hobart Brothers Co.Build your own arc welder booklet! | #1798738152 (worthpoint.com)

Talking about rectifiers, my brother has some off brand MIG welder he has had for years. Maybe 4 years ago it just stopped working. Yeah bad rectifiers, one of those dumb manufacturing ideas to use diodes that barely can handle the load, maybe planned that way. He hunted and hunted for replacements, I wanted to install larger capacity ones. He finally found some at an auto electric outfit and at a super good price. The machine works just great with no problems.
Dave, that is a cool book, the good old days.

This is the bore welder I have; a 308i series and it works well. There are more bells and whistles available in others but this one is easy to set up and use doing a good job. Kind of a poorly produced video but it does show the gist once it is set up. There are many other better produced videos available:

I would have loved having a bore welder! Hoping to get the drill press set up on the weekend. First I'll try to get the bore relatively smooth with a plug grinding wheel. Would hate to have a high spot destroy the boring bar and/or the bore.

Welded the bore up and started cleaning it up with a plug wheel on an angle grinder. A couple spots looked a little low so I preheated it and put a little more weld. It's looking really good but it is slow going with the plug wheel. I want to get within about 1/16" or so before I try the boring head. The hole needs to be about 3/16" bigger so I guess I'll be grinding for a while. I think the plug wheel would be faster than a flap wheel but I might try a 40 grit flap wheel to see.