Repairing wallowed out holes with a holesaw

[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

[Oldiron2]

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.

[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.

[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

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

[Oldiron2]

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.

Pictures would still show it better than a description. Also, adding your location to your personal details (so it shows in the upper right of your post) might allow someone near you to come over and give physical help. Sounds like you could use it.
Line boring involves boring a number of holes in a line, as is done with crankshaft and camshaft holes in engine blocks. As I understand it, you only have one hole, right?
If you can build the area up without hardening any of the involved metal and without any inclusions and then can make a smaller, concentric and properly centered hole, I'd think an adjustable reamer, or maybe just an end mill might do a better job of accurately enlarging the hole. Hole saws either rely on a pilot drill, or a rigid setup (e.g. a magnetic drillmotor) to position the hole, to feed it slowly, and to keep the saw cutting perpendicular to the surface. Same rigidity is needed for the end mill, and a reamer benefits from it too.
Carefully welding a mild steel disc (or ring) into the existing hole would allow positioning the new hole based on measurements from other points on the frame and (a disc) would also allow using a pilot drill, if needed. Bolting a large plate to the frame might allow the use of a mag. drill if directly mounting on the frame won't work for some reason. The drill unit probably could be rented, depending on where you are.

I have an electronics friend who tried using a small duster can for freezing something much smaller, and he said it was a futile effort. Dipping in dry ice+acetone freezes snails in seconds.

I haven't worked on modern heavy equipment, but have rebuilt lots of smaller equipment and made parts for odd stuff, including governor parts for a late 1800--early 1900 era Case steam tractor.

[M J D]

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.

[MinnesotaDave]

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?

[Welder Dave]

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.

[Lis2323]

Hoping Sberry will see this. He's done this type of repair with a hole saw.

Just pm him, Dave

[Welder Dave]

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.

[Oldiron2]

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

Cutting the solid section out and welding in, that is, replacing it with a solid section having the hole pre-sized, or very close to size would fulfill that requirement.

[Welder Dave]

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

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

[smithdoor]

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

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

[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.

[smithdoor]

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

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.

[tapwelder]

I would not attempt it with a handheld Hand drill unless clutched . If it catches then it will hurt.

[Willie B]

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

Been there.
I do NOT believe the boring can be done accurately with a hole saw.
The bore must be an interference fit matched to the OD of the bushing.
Yes, I've done it with canned air. I looked up the temperature & calculated at the time. I'm working with a lousy memory. Sticks in my mind I was able to shrink the bushing .0006" with canned air. Dry Ice would reduce the diameter of a 2-1/2" OD bushing about .003". Liquid nitrogen is about twice as cold ad dry ice & reduces size more than dry ice.
Last week I replaced two bushings in a Case "coupler". The last pair of holes in the bottom of the dipper get 5" long stepped bushings .003" reduced on one end. They are to fit very tightly in the dipper, & protrude into the "coupler", holding it in place. Coupler moves freely on reduced size of stepped bushings.
Switching buckets takes longer to get the snap ring off the pin than anything else.
Bushings aren't long enough to meet in middle, so one came loose & migrated into void in center of the "coupler"

Replacement bushings installed a few years ago were not as precise sized as Case supplied were.




After soaking in the liquid from upside down canned air, I'll guess to be liquid CO2, and coating bore & bushing with Loctite bearing setter, it was a 5 minute hammer job with a steel driver & 4 LB hammer.

The other bushing took two men & an 8 LB hammer, it did NOT go easily!

This time I cut an old bushing to shorter length to serve as a spacer. Should it loosen, it can't migrate inboard.

As for a washer to serve as a shelf for weld deposit, use a thick aluminum plate instead of the washer.

Like an engine cylinder, this bore must be a perfect cylinder shape, precisely aligned with the lower bore. Size is to absolute tolerance.

Either bore what you have bigger & make a new bushing, or weld & rebore to factory size.

[farmersammm]

Dave..........................

I see a bushing inside a large hole. Is this what's bad, or is there another hole that holds the pin that's wallowed out(one with no bushing)?

If it's just the bushing, it's a torch job.

Work the O2 stream into the bushing from inside the bore. Gently cut a slot through it to the actual boom itself. You'll probably notch the boom material, but if you just nick it, it doesn't matter. Think about what holds that bushing..................an entire 3" diameter hole. One little gouge in that perimeter doesn't hurt a thing. The bushing will bridge the gap(we're talkin' maybe a 1/8" wide gouge).

Do the cut where the material is thickest. The side of the bore closest to the tractor. You don't wan't to weaken the thin part that's further away from the tractor.

If you can........find some DOM that's slightly oversized on the OD. Measure the hole after you've removed the old bushing. Take a few measurements to find out an average. You'll probably want to size the DOM to the smallest diameter in the bad hole.

Turn the OD on the DOM to make for a .001-.0015 press fit in the damaged bore. You might go tighter, but it's risky. Size a pin to fit the inside of your new bushing made from the DOM.

Heat the bore, and drop the new bushing in, or lightly tap it in to be more honest. If it's a press in, or drive in, while the parts are cold...............you can use a locational fit epoxy from Loctite to fill out the irregularities in the bore. Go to the Loctite website to research these filler materials. I've used them with success.

You might have a bit of misalignment due to the bushing moving in the hole, and damaging it. Size your pin to to fit this variance. Go a few thou more undersize.

Look carefully, and you can see that the bore in the casting is egged. The new bushing is sized to fit the tightest part of that bore, while the egged portion is filled with the locational epoxy.

Smaller scale job years ago, but the same principle.

[farmersammm]

If you don't linebore it, it will never be totally right, but it'll work.

Another method if possible. Remove bushing, replace with DOM that's proud of the hole if possible, do same on other bore. Use a new, smaller, pin to line it all up, and weld the new DOM in.

Did every pin on my loader this way when I built it. No problems to this day. All pivots were lined up by eye. PITA, but exceptionally accurate when you use the tramming method I'm always talking about.

[Willie B]

I'll agree with you Samm, except for bushing removal. No cutting torch needed. Only need to heat the bushing to loosen it. In fact, the bushing I heated dull red last week to remove it, I cut to length for a spacer & it fit through the bores freely & by hand.

Most backhoe swing tower bushings are flanged. To cut one on a lathe, you'd have to start with a much bigger OD, & cut most of it down. 4140 is usually used. I'm not a machinist, but I stayed in a Holiday Inn once. It ought to be heat treated, then fine tuned again.

When Andy did it in my garage, he made spare bushings, (no heat treat) & he can replace when worn. Of course Andy is 34 years old & climbs cliffs as recreation. Manual labor does not concern him.

[farmersammm]

Every pivot was made in this manner. Rough cut holes in the plate, DOM inserted in the holes, pin spanning entire width of loader inserted in DOM, then the whole mess lined up with another pin further back on the loader using eyesight tramming.

Look at the wear on the pin. That's over 20yrs worth of wear..........or should I say NO WEAR. You can do stuff without line boring, and all the other fancy stuff. It's a matter of how desperate you are, or lack of access to expensive alternatives.

[farmersammm]

I'll agree with you Samm, except for bushing removal. No cutting torch needed. Only need to heat the bushing to loosen it. In fact, the bushing I heated dull red last week to remove it, I cut to length for a spacer & it fit through the bores freely & by hand.

That's way WAY better than cutting if you can do it. Absolutely!!!!!!!!!!!!!!!!!!!

[Sberry]

I shou8ld have taken pics of one we just did, I will look, maybe I did but the pics get tedious too. Test fit the bush,,, almost all wear on the 1 last time was egged shaped and in the oblong, I might have made a bush out of heavy pipe. Same hgere, not hi use machine and we put zerk in it. I welded out the egg and the saw just fits in the original bore and simply cut one side back to shape and was close enough to hold the bush which I welded in too. As I recall found A new chunk of pin. A drawbar with worn hole, get saw just fits in it, then weld egg and chase it with a saw. Last bush it took a saw, 15$ and needs a heavy gear reduced drill for slow speed. Was 2.50 I believe and took an hour or so to cut, went straight.

[Sberry]

This was the arm, prolly didn't get descriptive pic. Most of 5he time not really drilling a new hole but chasing buildup.
I will absolutely agree with the approach here if you can make it work on an old machine especially when cost is a concern. Take some time and mess with it. Saving a good chunk of money is as good as earning it. When I was coming out of a hole did the same thing, built a lot of stuff instead of buying and still do it if it makes $ sense or for speed.

[smithdoor]

That why I use a speed reduce to about 150 rpm.

Dave

I would not attempt it with a handheld Hand drill unless clutched . If it catches then it will hurt.