Hydraulic Die Forming Discussion Group
Cinch Block & Microfold-Beads

Jack Berry
berry2000@prodigy.net


I'm attempting to paste this material so MS Word is not needed to open it.
Using A Cinch Block to Make Microfold-Beads

Microfold-beads can be made by rolling a microfolded sheet of  metal into a cylinder and soldering the overlapping folds. Except for beads with extreme shapes I usually tack solder only at the ends of the overlapping folds. After collapsing the ends with pliers into a “rosette”, the rosette ends can be tightened and the bead given more curvature by forcing the ends into a cone-shaped or V-shaped hole (a “cinch block”). This gives a very symmetrical end and leaves no tool marks. The cinch block is easily made by drilling V-shaped holes into a block of end-grain hardwood using a countersinking drill bit available at hardware stores. I used a ½” bit and drilled to 3 depths with the same bit (see image) to accommodate a variety of bead sizes and shapes. The rosette must be drawn in “manually” with pliers to a circumference small enough to fit into the largest V-shaped hole. The bead is placed into the hole and force applied by hand while rotating the bead. Do this slowly and in increments checking for any misplaced folds which may require some “manual” movement. The edge of the rosette should always make contact with the sides of the “V” and not the rim. If the rosette collapses enough so that the bead is making contact with the rim of the hole move to a hole of smaller diameter (and lesser depth). Removing any sharp edges on the rim of the rosette with fine sand paper before cinching will increase the life of the block  but it will still wear with many uses. It can then be “dressed” with the same drill bit or make another. The block below is made of red oak with many holes (on the bottom side also) for a long life. I have also made one in Delrin but haven’t tested it yet. The cinching of the rosette can be made even tighter by holding the bead vertical with one hand (not leaning to the side is important) and gently tapping the protruding end with a rawhide or plastic mallet. Again, go slowly, rotate the bead  and check for shape changes as you proceed. Once the rosette is compacted and resists further movement, further malleting will cause an expansion of the “girdle” of the bead and a shortening from end to end of the bead. If a significantly “saucer” shaped bead is desired continue malleting carefully; however, the initial soldering should include a tacking at the center of the overlap as well as the ends to prevent opening of the seam with an extreme “saucer shape”. When the end of the bead gets very flat so that it cannot get into a hole in the block move to a plain flat surface and continue. The bead in the image was expanded in this manner. Here the girdle is displaced toward one end of the bead (non-symmetrical) giving a shape similar to a Native American clay pot. I believe Anne Hollerbach is planning to address how to control this shape in a future posting.


Cinch Block and A Bead


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