bi-metal hole saws

[orchardair]

Hatzers,
In preparation for attacking the metal tubing part of the project, I am looking at different tube notchers. They all require a hole saw, and I was wondering what sizes are required for the project.
Thanks.

[dougm]

You want to match the size of the hole saw to the diameter of the tubes you are mating TO. If you are cutting a 5/8 cross member to attach to a 3/4 longeron then you need a 3/4 hole saw as the 5/8 piece needs to fit around a 3/4 tube.

The only size hole saw I have used on the fuse is 3/4 as that is what everything is attaching to. I may need other sizes as I work through the landing gear or tail feathers, but frankly, after you have started cutting and grinding tubes for a while you get pretty good at roughing them out on a grinder as well. There were several I did on the grinder as it was actually quicker that setting up the joint jigger.


Good luck.

[orchardair]

Thanks Doug.
Here is another question along the lines of building the fuselage: assuming you are using the Meco Midget welding torch, which I understand is well loved, what size tip are you finding you use the most?

[dougm]

I am using the Meco. I usually used the #2 tip for clusters and the #1 for simple two-piece joints like a rudder pedal. I may have used the #3 for one or two big clusters, but I don't recall offhand. The #3 can put out a lot of heat if you aren't careful. Start small and work up in tip size... it's easier than blowing a hole in the tubing right at the start because your initial choice was too big.

Get some scrap tubing (i used some thin wall 3/4 tubing from Home Depot) to experiment with. Make a few clusters to get a feel for how to weld them and how much heat you need and where you need it. Doing that helped me a lot.

[orchardair]

Doug, your answers are much appreciated.
I hope you don't mind one more for today:
Are you using flashback arrestors or check valves with your Meco, and if so - are they attached to the torch or to the other end of the hose, at the regulator?
Thanks again.

[dougm]

No problem. I am not currently using those, but I should be. I plan on buying the ones that install at the torch.

[alvinsager]

Hi Hatzers,
I made my first fuselage before the joint cutters were available. I followed Tony's books and used a bench grinder with a wheel dressed round. Shortly after tacking the entire fuselage I was at Oshkosh and watched in amazement as someone was making a fuse fitting the tubes with an aviation snips. He never had to go to a machine tool and back to the frame. He said a pair of snips lasts for about one fuselage. His joints fitted up well enough, but not as perfectly as with the holesaw method. The tubing he was cutting had a .035 wall.
Just something to consider.
Al

[dougm]

I used snips on several of my tubes as well. I only did it on .035 wall tubing and certainly need to work on my technique, but it came out ok. For me, I found it was easier to "rough" cut the tube with the snips and finish it on the grinder... I'm not as good as the guy @ OSH. I also found that in certain cases the snips were easier that the hole saw.

[Nick]

Tin Man Tech (where you get the meco midget) has a great video about cutting and welding aircraft fusealges from tubing. They talk alot about how one builder will carefully notch out every tube with a tube notcher, make the fits perfect and then weld them, while another will cut them with snips, grind and weld them. In the end they are identical except for the fact that the snips guy was finished two months earlier. In my experience, tube notching is preferred if you're TIG welding. OA welding can fill in wider gaps so the tight precision is not required. Hope that's useful. The video is great in many ways if you're welding your first fuselage. I highly recommend it.

Nick

[mtaylor]

I'd also would recommend sitting in on the Tin Man's (aka Kent White) Oshkosh forums. Just remember that he sometimes can have an humorously abrasive sense of humor when asked a question. Don't take it personally. I've met him at Brodhead and he really is a nice fellow. He's phenominal with sheet aluminum! After my first Kent White forum, I went home and ordered the Mecco Midget and began an entirely new appreciation for welding!