fitting metal tubes

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Dress a grind stone to the radius of the tube, and simply grind the end of the tube to what ever angle is required. Virtually perfect fit. Otherwise, just mark the end with the template from the tube-fitter program and freehand grind with the hand grinder. Quicker and easier than the "joint jigger".

Aircraft builders use that method; I have 4 hours of tape from Kent White (possibly the best sleep-inducer ever committed to videotape, but great info) and probably 1/2 hour of it is him and another guy doing exactly that.

The consensus among the EAA crowd seems to be that the Joint Jigger and other hole-saw devices don't work well on tubing of 0.065 in. wall (16 gage) or less. On 0.039 or less, even 4130, they use tin snips first.

Ed Huntress

I expect it is the old problem of too few teeth in the cut. I use a hole saw type tubing notcher on heavy wall stuff. Works Ok. But for thin stuff it tends to grab or strip teeth.

Gary

Yeah, that's what it is. There have been letters to their publications about searching for really fine-toothed hole saws. I never saw a positive answer.

One of the EAA books, the one on metalworking, I think, actually is just a collection of articles. There must be a dozen or more just on the subject of cutting tube-ends for joints.

Ed Huntress

Ive had fair..fair..sucess by using one of the old cheap style hole saws with the interchangeable blades..best described as a piece of band saw blade, that slips into a groove in the body of the saw. Ive used pieces of the proper band saw blade tooth count, cut to length and placed in the groove and tightened down.

I need to make up a set of real ones someday. Id need to make a very very narrow tripanning blade and plunge a groove of the proper thickness for bandsaw blades. It only seems to work well if you are using heavy 3/4 or 1" blade material. The one I currently have, is the remains of one of those Sales Table rejects that comes with a handful of various diameter blades.

But it does work well enough with thin stock if using a fine toothed blade piece

Gunner

'If you own a gun and have a swimming pool in the yard, the swimming pool is almost 100 times more likely to kill a child than the gun is.'" Steven Levitt, UOC prof.

It appears to me, from the little experimenting I did with a "sample pack" of aircraft sizes of 4130 I bought a few years ago, that cutting thin-wall tubing to fit joints isn't much of a problem anyway. I now have a grinding wheel that's completely radiused, and an old 8" table saw with cutoff blade to make the angle cuts, and the two of them do the job well enough for me.

The transition wall thickness seems to be 0.062 - 0.065 in., commonly known as 16 gage (although avoid using that term when you're buying the stuff). Above that thickness, grinding the radius out gets pretty tedious. Below it, it isn't worth setting up a jig. You can do it faster by hand, cutting and trying as you go.

Ed Huntress

In my limited experience, if you flatten the stem of the tee slightly, you get a better joint, and have a lot less grinding to do. Theoretically, if you do a perfect job of grinding the round stem, you will wind up with a "saddle" shape, having two points that just reach the mid-point of the cross tube. The chances are they will melt back as you try to weld them. If you flatten the stem, you wind up with a more oval shape, which does not present this challenge, and is probably stronger. And it's certainly easier.

That's a good tip to remember, Leo. I do have to use extra filler when welding those "tips," and they can't be very strong.

Ed Huntress

Which way are you orienting the resulting oval? Long axis aliigned with the length of the other tube or across it? TIA

Ted