The 120 degree machine countersinking for flush rivets on the left wing spar was finally completed today. I knew this was going to be another mini project because there were a lot of holes on the spar to countersink, especially near the inboard portion where there is extra support for the wing walk area on the wing. Of course, machine countersinking takes far more time than dimpling, so overall it is a mini time sucking abyss.
Getting to this point has been a few days in the
making, but there has been a lot going on around here as of late, plus have
only really wanted to spend a limited amount of time in the shop so my arm doesn’t
get any worse. The elbow is beginning to feel much better now, but it does not
take much in the shop to make it complain, so have only been working an hour here
and there so it stays on the mend.
The home stretch - the end is in sight, only 18
more holes left to countersink.
In a previous post I mentioned I’ve been
spinning the countersink bit slowly by keeping the air to the drill turned down
to aid in eliminating chattering and hole elongation. Then discovered by starting and stopping the
countersink bit it appeared to cut faster than keeping the countersink bit
spinning slowly. That method truly does cut the countersink the fastest … at
least it does for me. Perhaps this is because the use of Boelube on the hole and
cutting bit makes a slick barrier for the bit when it spins faster. Don’t really know why, but one adapts to what
works well at the moment.
Finished inboard portion of the machine countersunk
left wing spar … notice the hole
spacing is tighter here compared to further
outboard as seen in the first photo above.
Now that the left wing spar is finally
countersunk, the left wing skeleton will take shape rather quickly as the ribs
are attached … and the available space at DOG Aviation will be diminishing just