Doubler Fabrication
Part made from 1.5mm (16 GA) sheet.
I needed a way to locate the bumper mounting holes. Transfer punch points are too tall to allow them to center in the sheet. If I flipped the sheet over keeping the transfer punch perpendicular would be a pain. So I broke out my trusty Harbor Freight 7 x 10 Mini-Lathe and made some bushings to locate the transfer punch and hold it perpendicular.
I scribed the rest of the spot weld locations and center punched them, locating centers by eye.
Then the profile was sheared where possible, band-sawed the rest, filed and sanded smooth. I made two in case I scrapped one later or needed one for the opposite side of the car.
Next, I machined some dies for use in a hydraulic press to make the dimples in the doubler. Back to the lathe. I machined the male side from aluminum bar since they would only be used a few times (and I had it already). The female bottom die was rough cut from hot rolled steel plate and finished on the lathe.
I planned to undersize the holes in the sheet to compensate for stretching of the material, then drill them to size after pressing. I opted to make reducer bushings to allow the use of a smaller fastener to align the dies, as well as to allow the use of a single bottom die.
The dimples caused the flat part to “oil-can” slightly but I was able to heat shrink it flat enough that it would be fine once clamped and spot welded in place.
I think that's it for parts fab. On to rust-proofing and welding things in.