AN960 Hardware Washer Wrenches
I Only Wanted a Bent Piece of Metal
The RV10.org wiki recommends using washer wrenches for the empennage assembly. I ignored that recommendation for a while, until I ran into one of those places where you really can't get your fingers in.
A washer wrench is a very simple tool: a thin strip with a notch at the end. Put the washer in the notch, position it over the hole, start the bolt and pull the wrench out sideways.
I could have ordered a set from Aircraft Spruce, but shipping four small pieces of metal from the US to Germany didn't seem worth it. So I decided to print my own.
The first thing I had to figure out was the notch size. The wrench grips the washer by its outside diameter, and the AN960 dimensions aren't quite as obvious as I expected. #6 and #8 washers have the same OD, while the AN960-10 is already 0.063" thick.
The washer diameter tolerance also matters. The specified OD tolerance is +0.020" / -0.005", so the notch can't simply be the nominal diameter. I made it slightly smaller than the minimum washer diameter and added a slot to let the jaws flex for the larger washers.
The original stainless wrenches are about 1.07 mm thick. That's fine for steel, but too flexible for a 3D-printed version. I made the handle 2 mm thick and reduced the working end to 0.8 mm so it can still slide underneath the washer.
The result is four wrenches with eight different sizes, engraved handles and a hole for a split ring.
The files are available on MakerWorld. I'd recommend printing the #10 / 1/4" version first. Those are two sizes that get used quite a bit on the RV-10.
And of course: this is a shop tool, not an aircraft part. Make sure it comes back out of the structure when you're done.
You can find the files here at Makerworld
PS: Sorry for using mm, I am still getting used to the 3456th fractions.