Here it is, Marvin's life saving tubing notcher. The biggest feature is the being able to adjust the "V" so you can place the tube you're notching to a location different from just being centered on the tube. I'm pointing to the adjusting bolts in this photo.

The notcher comes set up with a shaft suitable for a 1/2" chuck drill motor. I got it turned down to fit a 3/8" drill. It worked great with the smaller size drill. The block like assembly that the shaft goes through slides on the flat plate.

Adjusting the angle of the cut is accomplished by loosening the indicated knob and moving the slide/arm to the angle you need. The image below shows the little angle of the dangle protractor that I use for my work. (click HERE to see how to get one.)

Adjusting the angle is easy. Just measure the angle you need from your fixture, transfer it to your handy-dandy Marvin notcher, tighten down the knob and get ready to make some metal smoke. The hole saws are standard size saws that you can get at any hardware/lumber yard/ store and just screw right on. 

Making sure that you get the notches parallel when your notching both ends of a tube is easy. First, measure with a torpedo level on the top of the sliding tool/cutter assembly. It doesn't have to level, just make sure you notice where the bubble is.

Then adjust the tube you're going to fish-mouth in the notcher so that the bubble in the already cut end is the same as the bubble in the other end. Cut your notch and it's done.

Here are some samples of the types of joints, centered and tangent that you can make with Marvin's notcher.

Here's my Taube Fuselage. I laid up both sides, all verticals and diagonals in two evenings. One evening for each side. It makes what was normally a pretty tedious job, go fast!!

When Marvin's not out boring holes in the sky at 60 mph in his Siemens-Schukert, you can find him at the local dirt track going a heck of a lot faster in his race car(s). The notcher was originally developed to work with 4130 steel on race car frames like the one's behind him here.