Welding Tips and Tricks

In the near future, I will be joining two 2.5" 095 wall mild tubes with a machined inner sleeve. I've requested it to be a tight hammer/press fit. The end result needs to be as straight as possible.

My plan right now is to fit it up straight, clamp some angle iron in each side, verifying that it's still wobble free. Then hit it with quick tacks on opposite sides, moving the clamps after cooling and continuing to do so around the perimeter, verifying that it's straight, and if it moves, hitting the tack on the "long" side with compressed air.

Then after I have an autogenous root, go over it with filler, with the pulser on about 50/50 in the positioner, maybe even less bg like 20-30, doing maybe a half inch at a time on opposite sides.

Any tips for success would be appreciated! I'm kind of hoping that the tight fitting sleeve and clamps will keep it straight but I've never done it this way before so I'm not sure what to expect.

BTW I found this on youtube, it's absolutely adorable

https://www.youtube.com/watch?v=2vuGlcbDwKY

I still use the Mr. Shrink video in class - until I find a newer version

For your hammer fit, just heat up the tube a little and it'll slide right in. After it cools it'll be nice and tight again.

Makes sense, thanks will do!

same as putting a bearing in a case, heat the case freeze the bearing. it just falls into place!
craig

This needs to have no wobble when fully welded? I feel like that is almost impossible, but im not that experienced. I like the idea of clamping angle iron and tacking it in a bunch of places.

Ant428 wrote:This needs to have no wobble when fully welded? I feel like that is almost impossible, but im not that experienced. I like the idea of clamping angle iron and tacking it in a bunch of places.

Not a ridiculous tolerance but as close to no wobble as reasonably possible. It's a driveshaft section. The last one I did turned out well but I did it without a sleeve and I pretty much told the guy it wouldn't be straight but with the angle iron technique it actually turned out quite good, so much so that the owner of the shop that balanced it made a point to tell him that whoever did the shaft did a great job.

I assume the sleeve also adds strength to the weld? Do you burn into the sleeve as well?

BigD wrote:It's a driveshaft section.

I was wondering if you were doing a driveshaft. There's a place by my house that builds driveshafts, they repaired the PTO shaft off my tractor. They showed me their shop, they straightened my shaft before they balanced it by putting it in a large lathe and heating it in certain spots with a rosebud torch to take out the wobble. I thought they were joking before I saw the results.

I'm curious if a root and cap are even needed? At 0.090 wall thickness, why not leave the smallest of gaps and weld all 3 surfaces together in a single pass? A 3/32 wire should get you 100% penetration and cover... (I'm suggesting a gap of about 1/32). The angle iron/pipe clamp is a perfect method for insuring collinear alignment.

And I'm asking whether this would be satisfactory, not presupposing.

Sorry about the late reply guys, I was at PRI until yesterday and now laid up with the flu.

Ant428 wrote:I assume the sleeve also adds strength to the weld? Do you burn into the sleeve as well?

Yeah that's my plan currently, to hit the sleeve with the autogenous "tacking" pass and then a cover to get the whole smash to fuse.

cj737 wrote:I'm curious if a root and cap are even needed? At 0.090 wall thickness, why not leave the smallest of gaps and weld all 3 surfaces together in a single pass? A 3/32 wire should get you 100% penetration and cover... (I'm suggesting a gap of about 1/32). The angle iron/pipe clamp is a perfect method for insuring collinear alignment.

And I'm asking whether this would be satisfactory, not presupposing.

I'm not sure, probably not. I'm just trying to do it as well as I can think of. I want to make sure that the sleeve is nipped and the joint is as flush as possible to avoid stress risers. I'm going to try to set the pulser at a frequency where the ripples are nice and tight with the freeze lines being as minor as possible

Any strength added, or value of any type, if you were to drill 1/2" holes in the outer sleeve, and plug weld to the inner sleeve?

Others who know what they're talking about can answer that better but I wouldn't try that, feels like adding unevenly distributed welds can add stress risers and uneven tension. I want to make the joint as uniform all around as I can.

Turned out well! I still can't quite wrap my head around how much welds make metal move around. I know it does but I find it hard to "feel" like it's real. My friend machined it to such a press fit that he needed to use his mill table to assemble it. He adjusted it to a 0.002"ish runout and handed it over to me. I hit it with quick hot tacks every 120 degrees. Then did an autogenous root followed by a cover pass. It was up to almost 0.03" runout! I feared I'd need to cut it back apart, readjust and reweld but I went over with the pulser over the entire joint again and an extra pass where it was "long". Then hit it with compressed air as I checked it. Now it's back down to 0.0025" runout. I don't have a pic of the final weld but I'm very happy with it. It's barely above surface and the ripples are very tight and shallow (the final pass before the air gun was at a high pulse rate). I definitely penetrated to the sleeve so I think it's as good as I can make it.