Question about boring tube to make collars/bushings

I

ironwrx

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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.
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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.


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probably can't be calculated. if you have spare material you could make a test piece.
 
My first inclination is at least .03 oversize, but it's just a SWAG. The circumferential welds around the tube concern me less than the lengthwise welds.
 
MrWhoopee said:
My first inclination is at least .03 oversize, but it's just a SWAG. The circumferential welds around the tube concern me less than the lengthwise welds.
Click to expand...

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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