This Stearman airplane spinner was sent in for repairs after being badly dented. Alloy is 6061 T-6 aluminum, .063” thickness.

Measuring shows depth of damage.

Using the TM Technologies Curved Frame Model 3000 Air Power Hammer to shrink and straighten the damaged aluminum, without any annealing at all.

Our Air Hammer is well-known for having a wide range of adjustment – and this example shows how Kent was able to set both the BPM (blow-per-minute) rate and power so that the original spinning marks were left alone while the damage was straightened. Otherwise there would be stretching - and that would ruin the critical contour of the part.

This image shows how the heavily damaged area of the part was hammered and shrunk straight and how much filling and sanding would be needed.

Since spinners cover the center of the propeller and spin with the propeller, the damage repair must be very straight or it shows up right away. Templates (not shown) were used to gauge the repairs to insure trueness. The scrapes are still visible and must be brazed to fill. Sanding is very risky on any aircraft sheet aluminum part, so 320 grit is used only sparingly on the brazing, and gouges are either left alone or filled with Flux-core Aero Braze.

Final appearance looks very nice, and the backing plate fit perfectly. Some little gouges were left in as a reminder of the incident, and for “provenance.”