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Hole Flanging Tool

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  • Hole Flanging Tool

    Anyone used the ATS or other hole flanging tools?

    Am getting ready to try my hand at the bob stick method but thought I’d check here to see if anyone had good or bad reviews regarding these tools.

    4-Place Model 'B' Serial 1529B (with many years to go...)

  • #2
    I've seen those tools and wondered about them as well. I initially started trying to use the Bob Stick. Some people have great results but I found the time and amount of work required to be excessive for the quality of the final product.

    A lot of builders have found using a hydraulic press and some rubber mat to be the quickest method with very uniform results.
    Todd Weld
    Plans #1515B


    • #3
      For what its worth, here are my thoughts on these issues:

      I used only 3/4 inch MDF for all my form blocks. The forms were each treated with PC-Petrifier Wood Hardener which made them bullet-proof! I had no problem with reliabily the 3/4" MDF used through the entire process.

      The paired sets were used to router cut all the blanks. Before trimming and modifying them to be used as bending forms for the outer flange, I used a 45-degree router bit to cut the lightening hole flange recess; one LEFT and one RIGHT (inboard vs outboard orientation). I then used the rubber press method to bend the lightening hole flanges. This method worked fantastic!!! Quick, easy, and no time spent making male and female dies. The press was $140 from Harbor Freight and I got a stack of neoprene pads from Ebay.

      After the lightening holes were flanged, I then trimmed the paired forms down to the actual rib profile form using the original master and the router table. The edges were all radiused for both the lightening holes and outer flange edge (first with the use of files and sand paper, then found a router bit that worked great!). The exposed edges were again treated with a couple of additional coats of the wood hardener. I also routered out MDF backing boards 1/8-inch less than the bending forms and match drilled the jig pin holes.

      I first started the outer flanging by clamping the sandwich to the edge of my workbench and using dead-blow hammers. It needs to be very thoroughly clamped down very tight!!!! I used 2 hammers; placing one on the edge of the aluminum, uptight against the backing board edge, then hitting that hammer with the other one. Its extremely important to set the radius for the bend!

      After doing a few ribs with the hammers, I decided to try the flow forming method with an air hammer or rivet gun (see John Snapps' N3UW YouTube video). When I priced flow forming tools I thought the cost was too high, so I bought an air hammer and steel hammer bit from Harbor Freight, then went to Home Depot and got a box of rubber chair leg feet that fit tight over the hammer (ridges in the bottom of the feet were sanded flat). I also decided to switch from clamping on the table top to using a vise, in my case I used a Rockwell Jawhorse. I was very happy with my DIY flow forming tool and it worked great! Unique to the nose ribs, because of the aggressive curvature, I added flutting valleys to the form block, and used fluting pliers early on in the bending to start the flutes and ensure perpendicularity before the potato chipping started. Once the flange was bent enough, the flutes that I started laid down in the valley, where I used a rod and hammer to set them deeper. Be Careful when pounding the fluting rod into the valley that you down intersect the bend radius of the flange.

      Once out of the form blocks, I did not try hammering the flanges to bring them the rest of the way to 90-degrees. For the smaller ribs I used a pair of pliers and/or a hand seamer (protected with tape). When using the hand seamer, particularly near the trailing end of the flap and aileron ribs, you need to clamp it down tight and push hard against the table while bending it over past 90. For the larger ribs I built and used the Vans/RV style over-bending device (does this thing have an actual name???).

      The big ribs had to go back to the bench-top clamp method using all the form sections pieced together. For these, clamping alone was not enough, so I climbed on top of the bench and stood on the sandwich while hammering!

      I'm not sure if this will work, but here is a Google Photos link with a number pictures of these processes: what its worth, here are my thoughts on these issues:

      Last edited by kilohotel; 04-22-2019, 06:38 PM.
      Bearhawk Bravo #1508B - Scratch Build (wings)
      Northern Idaho


      • #4

        I flanged all the ribs as per Bob's instructions that came with my plans. Used a rubber hammer.

        I think my video of BobSticking is out there somewhere already, but here is a link to my web-server as well.
        I flanged all my lightening holes this way. Goes quite fast with almost no setup time required. No problems. Would do it this way again, no question about it.
        BobSticking does take a lot of hand strength; it helps to have milked more than a few cows recently.


        • #5
          Thanks for the replies, all. I'm still head-scratching regarding buying a press and some neoprene, using MDF male & female dies, or perfecting my bob-stick technique (is it Bob as in Bob Barrows, or bob as in the motion of a bobber?). I think I could get some harder wood or even just sacrifice an old freebie Harbor Freight screwdriver handle to re-try the stick method. I haven't had an opportunity to milk a cow, but maybe I can still put up with the hand cramps...
          4-Place Model 'B' Serial 1529B (with many years to go...)