A little bit of frustration over the last couple of days. When I started cleaning and prepping the F-705 parts fabricated from 2024-T4 bar stock, I noticed a lot of “mill marks” – gouges and scratches – that appear to be left over from the rolling process at the foundry. The stock was somewhat oxidized and dirty, and the marks weren’t apparent when I was fabricating bulkhead parts from it.

One example of the “mill marks” – longitudinal gouges on an F-605C spar carrythrough doubler –

…and a gouge on the edge of the spar carrythrough strap itself –

I had some phone and email conversations with Vans, who said that milling marks are normal. Nevertheless, I’m not really happy with using them for what I think would be a pretty structurally important part – maybe it’s just an attack of OCD on my part. I talked again with Scott Risan at Vans, and he offered to hand-pick good bar stock from their inventory and send me new material for free. Very cool!