Flanging Dies


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Last Update:

May 12, 2011



I tried the Bob Stick for flanging the lightening holes. It worked OK and did a good job if you took the Planter Bob short course and took your time. After about 5 holes, I reconsidered making flanging dies to save time. Instead of incorporating the dies into the form block, I made individual die sets. The female blocks are of 3.4” MDF. The male die is a 3/4” MDF base with a 1/2” ply or oak plug.

The female die was easy: Drill a hole through the block the same size as the hole you are going to flange. I used a 45 degree chamfer bit in a router to chamfer the edge of the die. You say the plans only call for a 30 degree flange? No problem! the springback of the Al will result in about a 30 degree bend. Set the depth of the chamfer bit to create the desired flange width (1/4” or 3/8” according to plans).


The male die was created with an adjustable fly cutter bit in the drill press. Adjust the bit arm to cut a PLUG (forget about the hole) just a tiny bit smaller than the hole to be flanged. This means from the center of the pilot bit to the INSIDE side of the cutter bit. Go SLOW and when you break through the material, you will have a 45 degree flange on the bottom of the plug. Glue the plug to a MDF base and let the glue dry.

You want the plug sized to just fit into the holes in the Al and in the female die. This will keep everything centered and your flanges will be even around the hole.

I also waxed both dies to smooth the bending process.


Being metal fabrication tool challenged, I didn’t have a 50 gazillion ton press around the house so I used a 6-inch bench vice and some bar clamps. Assemble the rib sandwich (I’m getting hungry now... be back in a minute...)



OK, where was I? All right, squeeze the rib sandwich together EVENLY top-to-bottom and side-to-side. Squeeze until you can go no more. I really don’t think you can mess this up. If it were possible, I think I would have found out.


Total time to flange a rib hole? Maybe 1 minute including making the sandwich, maybe less. So foolproof  I even allowed myself to have a real beer in the shop while doing this. Unfortunately you only need about one or two beers before the job is complete.

The Bob Stick may work fine, but Planter Bob could grow a whole new crop in the amount of time you save by making simple dies.

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