Dissatisfied with using the provided mandrels for Cleaveland Aircraft Tool’s close-quarters dimple dies, our Creative Homebuilder uses the hardened steel mandrels from 5/32-inch blind rivets. He feels that blind rivet mandrels are much stronger than those supplied with the dies and do a much better job of actually forming the dimple. When taken to the breaking point, they always load the die faces the same, as they are designed with a frangible stem in order to secure the blind rivet at its design load. This characteristic provides consistency in the dimpling process, so he pulls the mandrels to their breaking point. On very thin material (0.016-0.020 inch), he pulls to “feel and experience.”
The harvested mandrel, ready to slip out of the blind rivet and receive the close-quarters dimple dies.
Ready to go! The harvested mandrel with dimple dies installed, waiting for a piece of aluminum to dimple.
To date, the Creative Homebuilder hasn’t convinced a blind-rivet manufacturer to sell stand-alone mandrels (and he’s tried!), so he occasionally “harvests” the stems from blind rivets to ensure an inventory that is stored with the die sets in his tool drawer. The holes in the dies may need to be opened up a bit for the new stems, but the holes are still smaller (0.095 inch) than the #40 hole from which the dimple is made. He further notes that this technique does a good job on 0.020-inch aluminum and thinner.