Fabricating the web stiffeners^3h

Today I made F-704M parts, the web stiffeners.

The stiffeners are simple angles with several holes in them. They have nut plates attached to them, then both stiffeners are riveted to the bulkhead web. Two of the cover support ribs are screwed to the stiffeners through the web.

They are simple parts that should be easy to make. Cut the angle of proper size, match-drill the holes, and done. However, today I was not feeling it for some reason. My drill bit wasn't biting into the angle (I hate drilling these 6061-T6 angles, they are so gummy!), I forgot to center punch and my angle has slid. Then my angles would not fit, so I sanded them but managed to sand at an angle. I got one hole badly trilobed that even the reamer wouldn't clean it fully. I blew edge distance on one of the edges (got something like 0.210" where the minimum for -4 rivet is 0.219"). Likely, it doesn't matter for this part, but I kind of hated the result.

This is what I had initially.

This is what the fit looked like (I am using rivets simply for locating the parts). Note how the left one is sanded at an angle and is shorter than it should be.

They are probably fine parts, who cares, but I needed a bit of reassurance. So I decided to remake the parts on my mill. I measured the distance between the two outer holes with the caliper, which looked close to 4-1/8". Since we, humans, tend to use round numbers, I guesstimated it was exactly 4-1/8". Other holes seemed to be located with equal spacing (which gave me a 1-1/32" distance between the holes). Then I put the angle in the mill and machined it spending way too much time making it way too precise for the task at hand.

And behold, this is the fit of the new parts! There are no "left" or "right" now as they are exactly the same.

It dropped right in. There is a very slight misalignment (because I reamed the holes in the web with the manual drill when I made the original parts), but I can still put all three rivets plus two screws through the holes and everything aligns just fine.