I just bought a D5K that I am currently repairing. It has a missing bottom roller and all four 16mm mounting bolts were broken off. I have two out by welding on a nut which has proved to be difficult to do overhead, but nevertheless somewhat successful. I have been using 3/32 super missle rods and stud extractor rods. I have welded on the other two with no luck. I am considering torching the remaining two bolts out. I fairly proficient with torch but not a professional. First question: is there a reasonable chance of torching the two bolts out while saving enough threads to remount another roller? Second question: Torching will have to be done from bottom side blowing up with limited visibility. I have about one foot of clearance between the mounting rail and the ground. Would it be advisable to drill about a 5/16 hole through the broken bolt (about and inch deep in a tapped through hole) before trying to use the torch to wash out the bolts? I am thinking this would minimize the blowback in my face and allow the bolt to heat faster and therefore reduce the chances for damaging the threads in the bottom roller mounting rail which is about 1"x3" material. Thanks in advance for any experience and advice you can share.
Drilling the hole thru the center of the bolt works well if you can get started thru the hard spot where you have tried welding it. If you can make some kind of centreing jig that will help a lot ,either something that will fit into the existing hole if the broken bolt is deep enough.Or something with a 5/16" hole you can tack to the bottom of the track frame centered over the broken bolt. Get some good grade drill bits. Set up some kind of lever that you can push on the drill with ,i use a piece of 2X4 as a lever blocked against the back of my 1/2" Millwaukee cordless.Sounds ruthless on the drill but mines done a lot of them that way. Some good cutting fluid and slow speed with pressure and you should drill thru it. Once its drilled heat it good and hot with your torch.Have a solvent sprayer/atomizer hooked to an air line sucking out of a bucket of water ,hit it with this as soon as its hot ,cool it right down. Might take a couple of shots of this . An easy out might get it after that or go back to welding a small chunk of pipe onto it. If the hole is a bit messed up can you twist the bolt in until its clear of the threads or is the hole blind tapped? In summary the hole is a good idea ive done it with bolts and brake anchor pins on my cranes .The heat n shrink with air water is the key. Im not familiar with the D5K,last undercarriages i did were on D8 H s and old D9 s . we allways had the track frames off and upside down. welded tons of roller bolts out then .Filled them up with 3/32 7018 then a flat washer and finally a nut ,they allways came out. Those frames had a pocket for 1/2 the roller shaft if they were too beat up we cut the whole pocket out on both sides and jigged in new roller pockets. Usually the first roller aft of the idler.
Hey Charles welcome. I don't know about your torch skills, but with mine this would be a no-no. With the space that you have I do not see this ending with a good result. If it were me, I would make more attempts at welding the nut. However there are Guys on this site that have so much experience and so many great techniques that it reminds me I am a rookie when it comes to these big machines. If some of the Guys pick up on your thread I'm sure they will have some great ideas for you. Good luck! B-Crazy
I would not torch it, I would drill and heat it with a cutting torch but don't hit the oxygen, just let it sizzle a minute at that temp, then smack the bolt to upset it. Let it cool completely and it might turn out with a screwdriver. Or weld another washer and nut on.
Have to agree on trying to weld a nut on again. Would probably help if you could clean up the old weld a bit with a die grinder so you can get better fusion. I had a couple roller bolts I had to weld more than once to get them out. Putting extra weld to get it hotter might help but let it cool some before trying to remove it.
You are correct in that the bolt is now hard where I attempted welding in it. I was thinking about getting a carbide drill bit to get through that. The hole is a tapped through so there is a possibility the bolt could be turn out on either end of the hole. I think I going to try welding a few more times and then go to your suggestion if that does not work.
I am a little surprised that nobody that has posted has been a fan of torching the bolts out. I know it is done on heavy equipment but I don't know the success rate or the look outs to make sure it's successful.
Ive torched lots of bolts out when theres better access. and usually bigger bolts. You can wash the threads clean with some practice. Id avoid it in your situation. Are the broken bolts flush or broke inside the hole? If they are flush take a slightly smaller flat washer and weld that on first it protects the edge of the hole. Then weld a nut on .This work 99.9 % of the time.The Pictures are from a Vulcan air hammer that broke on us ,but same idea.
Again I am much less experienced with these bigger machines than most of the Guys on here. I think the torch (cutting) would be very useful when dealing with larger bolts. When I have used a torch for anything but heat on smaller of this size it has not been the fix I was looking for but only caused more work for me.
I have one broke flush and another about 1/4" down. I have taken bolts out like you are suggesting. I think the difference is the overhead welding and limited accessibility required in this case. I am going give the welding a few more try's. I agree the torch should be the last option, but I feel I am getting close to that point.
Is there room to put a nut on top and a longer bolt even if you have to weld a rod the nut and fish it in That would be a backup plan if you blow them out and no threads left as chances of success in saving the threads are low working upside down with no room chances of pain are high (; Sometimes carbide tipped masonary bits can get you though a hard bolt a solid carbide bit snaps very easy in a hand drill
Whoever said a picture paints a thousand words (or more) was right. Thanks for the posting those.
I think the nut on top might work if the threads are destroyed in the torching process. Thanks for the suggestion
See that bolt next to the tap, it didn't get hot enough at the end and came out harder than it could have. drilling the center and washing just a bit out through the center, or welding the center back up even, will heat the whole length and get it to shrink loose. That bolt on the upper right broke loose on the first try, then came out with another nut welded on to it, right? I would have drilled that one before trying to weld that deep, but if it's cast iron, the weld doesn't stick much, and doesn't do much damage as long as the rod is in the middle of the bolt.
Might be a little late here but last winter I had to do quite a few broken ones. If the bolts protrude a little, take a piece of heavy angle iron (however much clearance that you have) drill a hole near the end that the bolt will go through. Weld the angle to the bolt and get it hot. At that point you can either use an adjustable wrench or a big hammer to loosen it. Your success will depend on the heat of the bolt and your welding skill, you can get better penetration and coverage around the circumference of the bolt than in a nut when welding in a difficult place.
Bolts are too small in an awkward location to get at and see what you are doing. It would be way too easy to destroy the threads on the track frames. I suggested cleaning up the old weld so there would better fusion and more surface area on the bolt for a new weld to stick to.
I think overhead welding skill is my limiting factor at the present time. I have to start and stop a bunch of times to keep weld from dropping off the stud. I am using 3/32 rods and I am having to stop and chip a lot also. Maybe I should go to larger rods so that I could build up one larger puddle over the stud and washer.
That's definitely hurting your success. I've never done one overhead, and I can see it not working well, you want as much heat as quickly as possible into the bolt, the rapid heating is what does the work. Not a huge deal to torch it out, but I'd drill a hole first, and if you have the hole, then heating the bolt to burning temp (liquid on the surface sparking, and let it flow up the hole several seconds), that heat will shrink the bolt and it will turn out easier than washing it all out down to the threads and cleaning up the remains. IMHO.
It will be nearly impossible to extract the broken bolts cleanly using a gas axe and working upside down. The only really successful way to get them out cleanly is to invert the track frame. Yes, drilling a hole through the centre helps, but working upside down means you lose accuracy, and the slag can't get away fully. I once spent 3 weeks rebuilding my D6C undercarriage. I'd estimate fully half of the roller retaining bolts broke off flush with the track frame. I tore the frames off and inverted them and it still took me days of gas-axing and chiselling to get out all the remnant bolts. The biggest problem was Cat had installed roller retaining bolts that were too long, and the exposed threads on the inside of the frame had rusted, making unscrewing them cleanly almost impossible. The technique I used was drilling a central hole, torching as close to the threads as possible, then using a sharp small chisel and a solid seal pick (made from discarded stainless dentists picks), along with a pair of needle nose pliers, to pick out the remnant threads. I seem to recall I had to helicoil a couple, the threads ended up too badly damaged. By far the worst stud/bolt removal job I've ever had was taking the studs out of a 1920 Brockway truck engine block (actually, two blocks, because the block was split). These blocks had been in some terrible mineralised water that effectively bonded the threads. I had to weld nuts on 5 or 6 times sometimes to get out the remnants. And these were only Grade 5 studs - Cat Grade fasteners have the peculiar feature of hardening if heated to dull red, and simply left to cool. This is a feature of all low-alloy steels.
The bolt extractor rods are supposed to burn through the slag but using them overhead puts a wrench in the formula. Maybe getting a nut welded as best you can and then heating it red hot with a torch afterwards to super heat the bolt would work.
Yes, it can done with a torch. Bought a used PC228UU-1, 4k hours, 12 years ago and there was a letter on bottom roller bolts that was never performed. Factory overtightened bolts. Every roller was still there, but had at least one if not two broken bolts per roller. Burnt out, with my oxy/ acetylene torch approximately 50 bolts that had broken flush. And, put all new rollers on my 320DLRR, when it had 10k hours. Over a 1/3 of the bolts broke, almost all at the head. Tried torch heat, fast cool, torch heat slow cool, induction heater....nope, only got one out. Cut the rest flush and torched them out, in 10°F weather, on a muddy jobsite. It can be done, but, just like anything else, there is skill and a learning curve involved.
Keep at it with the welding, its the best way IMHO. try this. Ive welded about 15-20 nuts on a head bolt in a atv head once, frustrating as hell, but it worked. If your arc welding it, take your torch and pre heat the hell out of just the bolt, i mean get it glowing red hot, just the bolt, let it cool back to normal color but still hot then weld your nut on in AC as the switching action will "scrub " the rust bond. Pre heating it will allow it to stick to the bolt better. another trick Ive used is a mig gun and some copper tubing to protect the threads. Find a small piece of copper tubing that just fits in the hole, pre heat as above, shoot the wire in and weld the nut on. Other options are to drill it out with a hand drill, or if you can, a mag drill. If by hand again use a small piece of copper tubing to protect the threads and punch a small hole all the way through, keep working up to the minor diameter of the threads, then chase it out with a tap. If you have access to and can get a flat spot to mount it, then a mag drill is the way to go. Either way, dont use home depot bits, order quality stub length tilan /cobalt bits from shars, or mcmaster. If you have to drill them out and the threads are trashed, a helicoil can be just as strong. If you just nick a few threads, Remember , 3 threads give you 75% strength. Id stay away from torching them out if you don't have good "torch skills" its too easy to mess up the hole and cutting new straight threads for a helicoil is a pain in the but if you have slag and hard spots. Ive had good luck with a plasma torch, pulsing it, but the holes weren't deep. good luck
I have had success torching out the bolts I use a small tip but would be better if you took frame off. if you mess up the holes install a therad insert
I have licked a bolt or two out from below with a torch. You need good gear and a welding hood that you can set to grinding, so you can protect yourself. Welding leathers, etc. You cannot dally. The frame will heat up and then it becomes vulnerable. Once you blow through, go to another bolt and blow through. Let the whole thing cool down again and then re-orient yourself and lick it out a bit. Now the bolt is getting thinner and heats up quickly. I cut it out till I see the frame threads in a few places, then take a fine punch and hammer, and peel out the remaining bits.
The rapid heating and cooling is why welding usually works. I doubt it makes any difference if it's done with AC or DC. If that was the case then DC+ should work better because it has the deepest penetration and would bond better.