Repairing wallowed out holes with a holesaw

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I tried looking in the archives because I know it's been discussed before but nothing came up. Sberry has said he has done it frequently but other's may have experience with this as well. Line boring just isn't feasible at this time. The top swing pivot on my backhoe has a badly wallowed out hole that needs to be repaired. I'm fairly certain I can weld the hole up. I was going to tack a washer on the bottom of the hole to help make a shelf for the weld build up. This would also make it easier to get the weld right to the bottom of the hole without burning the bottom edge off. The bushing is 2 inches thick. What I need help with is the following:Do I need to enlarge the hole prior to welding so I am not cutting into the Heat Affected Zone or is it OK to just weld the hole as is?How much smaller diameter does the weld have to be in relation to the hole saw? Being 2" thick I realize I will need at least 1 relief hole to remove the chips from the hole saw. Is 1 hole enough or is 2 or more better and what size should the hole(s) be? Is 1/4" enough. I'd have to put enough weld to be wider than the drill bit. I plan to tack a plate at least 3/8" thick with a hole the same size as the hole saw to use as a guide for the hole saw. Could the hole possibly be done with a hand held drill? Should the guide plate be as thick as possible?I have a big drill press that I think will fit the space but it would be quite tricky to align and square everything, especially being on a gravel floor. I'd have to move the drill press with the skid steer and then wrestle it into position on some plywood or boards. If the drill press would do a superior job then maybe it's worth all the trouble to set it up???The hole needs to be 3". Will a 3" hole saw leave an accurate hole within about .005"? I read about someone sanding the outside teeth of a hole saw down to have a slightly smaller hole that could be finished with a flap disc. Would this cause the hole saw to not cut as easy?I need to do this repair on a really tight budget as I'm still waiting to hear if I will be approved for early disability. I have no other income and could never work a full time job. I can do about an hour at a time and that's pushing it. My back aches badly and I have very little energy. If I have to kneel down, I can barely get back up. It will take me quite a bit of time but that's OK as long as I can get the hole repaired satisfactory enough to fit the hardened bushing that goes in it. It's a shrink fit so I might need to get some dry ice to freeze the bushing prior to installing it. That brings up another question, has anyone used an aerosol computer duster upside down to freeze parts for fitment? Thanks in advance
Reply:Is the part still attached to the machine?  Could you post pictures showing the part, showing that part of the machine where the part is attached (if it still is), etc. so we have a better idea of the situation? Do you know if alloy steel is used for the part? Might it be easier to remove the section with the hole and weld a new section with an accurately-sized hole back on? No, A hole saw won't do an accurate job, but an adjustable boring head would. I doubt a drill press would be rigid enough for the work with one though. Have any friends who own a milling machine? You need the hole to be fairly accurate to properly fit the hardened bushing right.A small can of 'duster' won't do much with the size parts you're working with. A CO2 cylinder (beverage or welding size) with just a hose would though. I used to have access to liquid nitrogen and used it once for a similar job. Worked well.Last edited by Oldiron2; 14 Hours Ago at 01:12 PM.
Reply:People have done it with a hole saw before so I know it can be done. Maybe a smaller hole saw and then careful grinding with a flap wheel? It is the main frame of a backhoe, it can't be taken apart or removed. The top swing pivot is a 2 inch thick mild steel bushing welded in a 1 inch mild steel plate that is part of the main frame. The backhoe stabilizers and hyd. controls also mount on this frame. I am able to move the backhoe boom over to give access to this bushing. The repair has to be done on the machine. I can use a spring tension bushing if the hole is too large for the hardened bushing but I'm hoping I can use the hardened bushing. What I am looking for is some assistance from someone who has experience using a hole saw for this type of repair. Line boring is out of the question. The hardened bushing is 2.5 inches ID and 3 inches OD and 2 inches long. It's not a really big part that needs to be froze.Last edited by Welder Dave; 13 Hours Ago at 01:58 PM.
Reply:What is this for?Sounds like a earth moving equipment repair. If so the easiest way is to line bore very simple to do .Dave

Originally Posted by Welder Dave

I tried looking in the archives because I know it's been discussed before but nothing came up. Sberry has said he has done it frequently but other's may have experience with this as well. Line boring just isn't feasible at this time. The top swing pivot on my backhoe has a badly wallowed out hole that needs to be repaired. I'm fairly certain I can weld the hole up. I was going to tack a washer on the bottom of the hole to help make a shelf for the weld build up. This would also make it easier to get the weld right to the bottom of the hole without burning the bottom edge off. The bushing is 2 inches thick. What I need help with is the following:Do I need to enlarge the hole prior to welding so I am not cutting into the Heat Affected Zone or is it OK to just weld the hole as is?How much smaller diameter does the weld have to be in relation to the hole saw? Being 2" thick I realize I will need at least 1 relief hole to remove the chips from the hole saw. Is 1 hole enough or is 2 or more better and what size should the hole(s) be? Is 1/4" enough. I'd have to put enough weld to be wider than the drill bit. I plan to tack a plate at least 3/8" thick with a hole the same size as the hole saw to use as a guide for the hole saw. Could the hole possibly be done with a hand held drill? Should the guide plate be as thick as possible?I have a big drill press that I think will fit the space but it would be quite tricky to align and square everything, especially being on a gravel floor. I'd have to move the drill press with the skid steer and then wrestle it into position on some plywood or boards. If the drill press would do a superior job then maybe it's worth all the trouble to set it up???The hole needs to be 3". Will a 3" hole saw leave an accurate hole within about .005"? I read about someone sanding the outside teeth of a hole saw down to have a slightly smaller hole that could be finished with a flap disc. Would this cause the hole saw to not cut as easy?I need to do this repair on a really tight budget as I'm still waiting to hear if I will be approved for early disability. I have no other income and could never work a full time job. I can do about an hour at a time and that's pushing it. My back aches badly and I have very little energy. If I have to kneel down, I can barely get back up. It will take me quite a bit of time but that's OK as long as I can get the hole repaired satisfactory enough to fit the hardened bushing that goes in it. It's a shrink fit so I might need to get some dry ice to freeze the bushing prior to installing it. That brings up another question, has anyone used an aerosol computer duster upside down to freeze parts for fitment? Thanks in advance
Reply:

Originally Posted by Welder Dave

People have done it with a hole saw before so I know it can be done. Maybe a smaller hole saw and then careful grinding with a flap wheel? It is the main frame of a backhoe, it can't be taken apart or removed. The top swing pivot is a 2 inch thick mild steel bushing welded in a 1 inch mild steel plate that is part of the main frame. The backhoe stabilizers and hyd. controls also mount on this frame. I am able to move the backhoe boom over to give access to this bushing. The repair has to be done on the machine. I can use a spring tension bushing if the hole is too large for the hardened bushing but I'm hoping I can use the hardened bushing. What I am looking for is some assistance from someone who has experience using a hole saw for this type of repair. Line boring is out of the question. The hardened bushing is 2.5 inches ID and 3 inches OD and 2 inches long. It's not a really big part that needs to be froze.
Reply:Can't you just cut the weld on the old bushing and knock it out? Just don't see the hole saw thing being feasible as you really have no way of controlling it's exact placement. Hole saws always cut oversized, 1/32"-1/16" over isn't uncommon. Annular cutter would be a better choice but expensive. Line boring is really the only way to do this without it turning into a hacked up mess. It really wouldn't be that difficult to rig up a boring bar supported by either a pillow block or flange  bearings.
Reply:I think it's easier to have a repair "bushing" made that you can weld in.  That way the hardened bushing can be pressed/hammered into that bushing.The weld-in repair part really only needs a torch cut hole.Will that help your situation?Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:Needs to be solid steel without a sleeve. There's a lot of stress on it. It's a 2 1/2" pin. I previously ripped the whole top pivot off and bent the lower swing pivot that is 1 1/2" thick. I'm basically looking for an alternative to line boring. It has been done successfully before with a hole saw. It might take a long time but that's OK. There's no room to put any kind of bearing on the bottom of it. I was going to use a steel plate with the proper size hole tacked on top to be a guide for the hole saw. I could use a smaller hole saw and a die grinder with a flap disc for final sizing if required. Hoping Sberry will see this. He's done this type of repair with a hole saw.
Reply:

Originally Posted by Welder Dave

Hoping Sberry will see this. He's done this type of repair with a hole saw.
Reply:I just did. I know he's done it on more than one occasion so could use a little guidance so I have the best chance of success. Nothing beats experience.
Reply:Is there some reason you can't/won't post pictures of the area of the machine needing repair? Or tell us roughly where you are? Needs to be solid steel without a sleeve. There's a lot of stress on it. It's a 2 1/2" pin
Reply:

Originally Posted by smithdoor

What is this for?Sounds like a earth moving equipment repair. If so the easiest way is to line bore very simple to do .Dave
Reply:I did line boring To me it was very fast and works every time. Still have a lot of DOM tubing If was not for cancer I would be doing that work today. Dave

Originally Posted by Welder Dave

Line boring is also the most expensive way. It's a track loader with backhoe and  is an hour out of the city. I don't want to spend a couple hundred bucks just on travelling time and then hundreds more for line boring. If it really came down to it I could manually grind it with a die grinder but that would be an extremely long and tedious procedure with lots of measuring. If the hole was slightly oversize I could drill and tap for a couple set screws to hold the hardened bushing in place. Looking online people have successfully drilled accurate holes in thick steel with a hole saw. Some even claim a hole saw is more accurate than a drill. An annular cutter would be the ticket but at 3" dia. would be cost prohibitive for 1 hole. I live in Edmonton, Alberta. There isn't enough meat to cut the existing bushing out. Even if there was I would have to remove the boom and rotary swing cylinder and then use about a 2' long piece of 3" DOM turned down .005" as a line up pin. Been there done that when the bushing and plate its mounted in ripped completely off. It was a big repair job but probably one of the best repairs I've done. I had to cut a V in the 1" plate on both sides and welded it vertically up with 3/32" 7018. Then I carefully ground it so it looked like new. The hole got wallowed out because the inside bushing turned inside the bore and dropped down about a 1/4". Here's a pic - hopefully


Reply:Obviously if you have the equipment line boring would be the way to go. When you have to hire it out is very expensive. If this was a production machine I made my living with then I'd consider line boring. For something that gets used less than 100 hours a year I need to budget appropriately.
Reply:The first time I did line boring I used a 1/2" hand drill motor and pillow block bearing. I use variables speed controller to reduce the speed to about 150 rpm.Today I use a mag drill with u-joints and pillow block bearing. They do manufacture a line boring machine but mag drill about something and they use pillow block bearing too. Dave

Originally Posted by Welder Dave

Obviously if you have the equipment line boring would be the way to go. When you have to hire it out is very expensive. If this was a production machine I made my living with then I'd consider line boring. For something that gets used less than 100 hours a year I need to budget appropriately.