Question about boring tube to make collars/bushings

[projectnut]

I don't think you're going to have to bore it more than .010 at the most. I did a similar project many years ago when building a small end loader from scratch. I also used the same process when making fork attachments and a log splitter for the machine. In this case the pins were 1 1/4" on the log splitter frame and 1" on the loader bucket arms.

The DOM was welded into the tubes, the ends extended about 3/8" beyond the tube faces. They were ground flat, then reamed with an adjustable reamer and a shaft collar was slipped over and set screwed in place flush. The reamer was set to .005" oversize to allow grease to be pumped into the joints.

The first picture shows the pins for the hydraulic cylinders in the loader arms. The second and third pictures show the splitter carriage in pieces and partially assembled. The final picture shows the splitter carriage fitted on the machine.

 

[Provincial]

The bore will not be straight (bigger in the unwelded area than the welded area) so the pin will be tighter in the welded area. This will cause more wear and concentrate stress on that area of the pin.

The best fit would be from line boring the assembly after welding. The next step down would be to ream or hone he bore in the welded area until it matches the size of the un-welded area. The least effective way is to use flapper wheels to sand the welded areas a little bigger to minimize the bore diameter difference.

 

[Jake M]

Hi I have a fabrication job that I am working on involving taking heavy wall (1/2” thick) DOM tube, cutting it to length, and then welding the Bushing/collars through 1/2” thick plate extensions, which will be welded to the top of an backhoe bucket. This completed weldment will be to add “thumbs” to the backhoe bucket. These components will be welded around their circumference on their faced and beveled ends flush with the plate frames of the bucket.



My question is this: after I cut this tubing to length, and bevel the ends for welding, I need to bore these pieces out to an appropriate dimension before I weld these components to the bucket and the h-beam thumbs. How much do I need to allow for the bore of these to shrink when I weld these components to the bucket frame and the thumbs? I want to end up with a good sliding fit, but do not want to have to line bore or ream them after welding. The "pins" for this project are 1-1/2" and 1-3/4". The bushing stock is 2-1/2" and 2-3/4" respectively.

Boring those ahead is going to be problematic, and it's not the diameter shrink you're worried about, it's the movement of the whole thing. The weld is going to make the entire bore crooked by more than an appropriate grease clearance. Which leads to the pin made sloppy or having it hammered in "around a corner", which precludes grease from the contact points, and short lived either way.. This really wants to be align bored after it's in place.

Typically on a machine that's tight enough to stay tight (not loose enough to beat it's self apart...), you're looking at 2,3,4 thousandths of clearance between the pin and the bore. Two being appropriate and durable, but obnoxiously tight By five or eight thousandths, it's not sloppy at all, but the wear is increasing geometrically.

How much use is this gonna get? If we're talking about a low use machine that's gonna have it's hours measured in hundreds and not thousands... Fifty thousandths on a pin works fine AFTER everything's worn in and "mated". That would put put play in a bucket for sure, but not digging swails right away.

 

[MrWhoopee]

I’m guessing that SWAG means some kind of guess? I did talk to another weldor friend, and he basically suggested the same thing 1/32”. It also turns out that there won’t be lengthwise welds.


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Scientific Wild-Ass Guess.

 

[machPete99]

Instead of line boring you could potentially just run a reamer through it.
I did something similar a while back, used an adjustable reamer and made a cone and guide rod for it to get the final fit.

On adjustable reamers, don't get the ones with the individual blades (these always bind/chatter), get the type that is bored through the middle and uses a wedge screw.

 

[toprecyler]

There is a lot of “ depends on this “ parts that come to mind here to determine an appropriate answer.

Weld prep and actual welding is biggest one. The how and placement of welds will be the biggest factor. And how much weld is applied.

Assuming you will have the pin and thumb parts installed when tacking together and as you weld, it may hold it self fairly straight. At least good enough for the hydraulics to work it. It will probably warp enough that it will have a lot of drag though.

I would have at least .010” clearance, up to .030”

Are you planning on having grease zerks? Maybe cut a grease groove in bushing too.


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[Flyinfool]

What if you just machine the shrink clearance in the areas that will shrink. Most of the bore will still be supporting the loads. The area to the inside is the hardest to get to for fixing any shrink, this area is also carrying the least amount of load. Make sure you have adequate clearance there before welding, The outer end is easy to get to to clean up any shrink.

 

[ironwrx]

There is a lot of “ depends on this “ parts that come to mind here to determine an appropriate answer.

Weld prep and actual welding is biggest one. The how and placement of welds will be the biggest factor. And how much weld is applied.

Assuming you will have the pin and thumb parts installed when tacking together and as you weld, it may hold it self fairly straight. At least good enough for the hydraulics to work it. It will probably warp enough that it will have a lot of drag though.

I would have at least .010” clearance, up to .030”

Are you planning on having grease zerks? Maybe cut a grease groove in bushing too.


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Yes, I am planning on zerks, and I like the idea of grease grooves as well. Do you have any suggestions how to cut the grooves?


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[Weldingrod1]

Die grinder?

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