Filling Aluminum

There are ways to fix this as long as you have sufficient edge margin
AND the properties allow this to be done.
Use a freeze plug. Turn a slug of material to a shrink fit dimension.
Freeze it in dry ice, drive it in the hole. After the part is back to room
temp.
Redrill the holes in the correct position. This makes you do a little
figuring,
like the minimum size necessare to "clean up" the hole before machining the
slug.
If the gear leg is sandwitched and the plug is encapsulated, carrying only
shear
loads, this is a piece of cake. If the hole is for a tension load, then the
"bushing"
you machine will have a shoulder that is 2D, and an appropriate thickness.
It
isn't that hard to do....... Just engineer it correctly and march on.

If the hole is NOT in a place that will carry a fastener AND you have
sufficient edge
margin and mechanical properties........ Touch countersink the holes and
double flush
plug rivet. Use a countersink of about .030 depth on both sides. 100
degree will be fine
BUT the BOOK OF KNOWLEGE (ac43-13) calls for 82 degree NACA method riveting
to do this..............

Your mileage may vary,

Scott.