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EAA Experimenter

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Shop Tools

By William Wynne, EAA 331351, WilliamTCA@aol.com, http://FlyCorvair.com

William is best known as an engine guy, and specifically known as the Corvair Authority. In the last 20 years he has fabricated and welded significant parts and assemblies that have flown on more than 100 different experimental aircraft.

I personally find welding very rewarding. It requires an investment of money and time, but the skill pays a huge return on this investment. With the right instruction, anyone can learn how to weld, and I encourage all homebuilders to give it a try.

Shop Tools

Shop tools

These pictures illustrate a tool I have kept in my hangar for many years. It looks well worn because it gets a lot of use. Basically, it is the three tools used most in cutting and fitting steel tubing on one mobile cart.
The tools are a 14-inch Milwaukee cut-off saw with an abrasive metal disc, a 12-inch direct drive disc sander with a 40-grit self-adhesive pad, and a 6-inch grinder with one grinding wheel and one wire wheel. The abrasive wheel has rounded profiles, one for 1/2-inch and 5/8-inch tubes and the other for 3/4 inch and up. The wire wheel is for general cleaning and a little de-burring.
Two of the photos show a spark suppressor (built of scrap aluminum) attached to the saw. Since the blade is an abrasive wheel, a shower of sparks is common, and the suppressor becomes useful for containing them. The bench was made from scrap plywood and old angle iron. Fabricating the table itself is a good welding tuneup project.
Before turning on the power, put on gloves, goggles, and hearing protection. In operation, I cut the tubes to length with the saw, which is capable of severing a 3/4-inch 0.049-inch wall 4130 tube in one to two seconds. The saw is also good for making angle cuts to 45 degrees. Step number two in the process is the disc sander. This is very good for rapid de-burring or for sanding 45-degree cuts to 60 or more degrees, quickly. The very course  paper (40 grit) works quickly, lasts longer, and runs cooler than finer paper. Last stop is the grinding wheel, where the angled cuts are radiused to allow the cut tube to lay down on another round tube. Practice makes the process quick and accurate. Most diagonal tubes in a fuselage have two different angles on each end, with each having some radius on them. When I am on a roll with this tool I can make such a tube in two to three minutes, with fits so close that you cannot stick a 1/16-inch welding rod anywhere in the joint.
One of the key things about the setup is that the saw table, the sander bed, and the grinder pedestal are all the same height. This way, when you have a long piece of tubing in the saw it is supported level by the other tools.

Shop tools
A close look at the grinder base shows a small angle that is parallel to the saw’s fence. The sanding disk sits back slightly from this line.

The mobility of the tool allows you to bring it right up to the location of the work. This has two distinct advantages. In many shops, the fuselage jig is 20 feet away from the tools, causing the builder to walk several miles in the process of fitting 30 tubes. Getting closer eliminates the commute. Second, I have often found that I can study the fit of a tube, mark it with a silver grease pencil or a silver marker, and then walk 20 feet to the other side of the fuselage table to get to a grinder, only to find upon my return 55 seconds later that something was lost in translation or motion, and argh, it’s too short! Having the tools 2 feet away, on the same side of the table, will not only save the walking, but also does a lot for the accuracy of your fitting.
There are a lot of ways to fit tubing, from machining each one independently on a mill to having computer-numerically controlled (CNC) equipment do it for you. (A really good look at tubing fits can be seen at my buddy Don’s website, www.VR3.ca/tube_profiling.html.)

The tool in the photos is a practical and efficient solution between extremes. It has served me through a whole lot of production. If you have had your eye on a steel tube homebuilt, but thought it would be too hard to build, think again. Proper training, practice, and a tool like this can put that plane within your grasp.


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