A unique method to hold tabs while welding to round tube
By Mark E. Eminger, EAA 379500
Mark Eminger, a Christavia MK1 builder from Cloverdale, Indiana, sent us this very helpful construction tip. He’s designed and built a very simple jig for holding clip-nut tabs while welding them to fuselage tubing, aiding the builder in such a way that could easily reduce setup time by at least 5 to 10 minutes per tab.
The problem I encountered while welding tabs to my fuselage was how to hold them firmly in place while I tack-welded them where they belong. My project has over 200 of these tabs to attach, so the time savings should really add up. The jig is made from common materials found at your local hardware store and can be quickly put together in about an hour.
Click each image for a larger view
The required materials consist of a 1 x 1 x 5 inch length of aluminum angle, two #8 machine screws, five rare-earth magnets, and some Super Glue.
- Cut the aluminum angle into two pieces, one 4 inches long and the other 1 inch.
- Cut 2 inches out of the middle of the 4-inch-long piece, and deburr the sharp edges.
- Take the 1-inch-long piece and slowly smash it between your vise jaws to increase the angle to greater than the original 90 degrees. This angle will be adjusted through trial and error to get just the right fit.
- Next, drill two clearance holes in the 1-inch piece for the #8 machine screws and transfer these holes to the 4-inch-long piece and drill pilot holes. Then tap the holes for the #8 machine screws.
- Glue the rare-earth magnets as shown in the photos above, and when cured, set a tab in place and check, adjusting the angle accordingly.
I wanted my tabs to be welded just below the top of the tubes so to leave room for the weld and the clip nuts. A channel can then be milled or filed to hold the tab perpendicular to the tube and firmly align.
When using on different diameter tubing, you can slot the two clearance holes to allow further adjustment of the tab location. Once tacked in place, the tab jig can be removed to provide full access for finish welding.
The finished jig appears to work very well at holding the tab firmly in place.
For questions, I can be reached at firstname.lastname@example.org.