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Enlarging Bore of Heavy wall tube


Nov 9, 2012
South Dakota
I need to make a reinforcement for a hydraulic outrigger cylinder. It is 5 1/4" OD and 34" long. Just got done rebuilding the cylinder with a new barrel as the original bent due to side pressure from usage. The cylinder is currently mounted hanging from the top with a 12" cast clamp that surrounds the cylinder. It bent just below the bottom of this 12" clamp. My thought is to make a new clamp that is the length of the cylinder (34") and replace the 12" clamp with the new 34" clamp. The problem is material the right size. I have sourced locally a 7" OD / 5" ID tube. I would need to bore or otherwise machine this tube to 5 1/4" ID and then slit it longitudinally to make the clamp. Slitting I can do on my old Horizontal mill. I can't really come up with a way to bore the tube to 5 1/4" 34" deep. Considered making a boring bar out of the old 3 1/2" cylinder rod that was scored and clamping that to my carriage with an appropriate riser clamp, but all that would have to be made. Not at all familiar with Horizonal Boring machines. Is this something someone with the right size machine could do? Hoping someone can give me a better way to make a strong 5 1/4" ID reinforcement for this cylinder.


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This looks more like a place for a stabilized drill, similar to a deep bore drill or ejector drill, where "pads" (usually carbide) are brazed to the drill slightly behind the cutting edge to stabilize it and prevent drift. An old AMEC would be a good candidate for modification. And allow indexing a new to if you accidentally burned up the old one.
But it will require a LOT of coolant for that method.
Here's a "gun" drill type
The pads do a lot for centering control and allow single pass Operation, a boring bar that size is going to give plenty of trouble unless you have a lot of spare time.
there are many ways to skin this cat.
best way is someone with a 2"+ boring bar and a large lathe that is at least 8 ft of travels for the carrage. with that it would be easy to do.
Roto broach and a long travel machine, but I think Hougans only go to 4" diameter.
Cutting chips are flushed out with the pressure of the coolant.
*But a big machine and a boring bar is likely the way to go.

Thanks for the responses guys. I like the gun drill picture. It is similar to what i was thinking. I check also to see if there's someone with an HBM.
Those gun drills can occasionally be found cheap on eBay. They're also known as ejector drills, and BTA drills (Boring Trepanning Association).

I prefer them to traditional gun drills but they're not ideal for the small (1/2" x19") deep holes that I drill most commonly.

If anybody needs some brazed type in 10 mm, I know a guy willing to move them cheap!


These are the tungaloy version, Allied Machine and Engineering also makes a version that uses standard AMEC spade drills. Lots of designs and variations out there.
Another way to do this is buy a piece of tube with an ID bigger than ideal, then turn up some sleeves of a size you can easily machine, and push them in.
Another way to do this is buy a piece of tube with an ID bigger than ideal, then turn up some sleeves of a size you can easily machine, and push them in.

If it's a reinforcement for a hydraulic cylinder the right way to do this would be to bump form two halves from 3/4" T1 on a 500+ ton press brake.
I'd prolly just bore a 12" piece and use it to extend the existing clamp rather than cut off/replace existing clamp. Are your welding skills up to crane outriggers?
A guy with a line boring setup can do that. Need to fixture the tubing to something solid to take the torque, but not really a big deal. Heavy equipment guys are the ones to call about pricing, and whether they'll take it on.

Only thing to think about is.........what kind of tubing you have. If it's A500, or some other grade of mild structural, it's good to go. If it's some sort of API tubing, you need to determine whether it can be welded successfully. Some of that stuff has a ton of carbon in it, making it difficult to weld without embrittlement.

Also............is it ERW pipe/tubing? A seam plays hell with cutting tools. HRS is best for what you want.