After retrieving my Uni-bits from the hangar, I was ready to start preparing YAB. What's a YAB? Oh, that's "Yet Another Bulkhead." I left out a letter or two in the interest of brevity.
Twenty-three nutplates. Two countersunk holes each. Plus another six #30 holes to be countersunk with the 120° bit. That means CS-4 blind rivets instead of squeezed #4 rivets sometime in my future, so there is that. But it still added up to fifty-two holes to be countersunk.
I shouldn't sound so down about it - I actually like countersinking. The micro-countersink thingy has a solid feeling of precision mixed with get-outta-my-way brute force that I somehow find enjoyable to use. But still... fifty-two! That naturally left a lot of metal shavings scattered all over the work bench, so I somewhat absently lit up the powerful shop-vac to apply some housekeeper's suction to the mess. As I was vacuuming around, I heard and felt a thunk in the hose and saw something larger than a metal shaving go flying up the nozzle. I thought it must have been one of the little lengths of cut up wooden paint stirring sticks that I keep around to support thin aluminum when I cut it with the band saw. I was thinking of just letting it go at that, but thought better of it and opened the vac to see what I had netted.
Oh. A little plastic bag filled with the three not-currently-in-use countersink bits. I would have never found those!
Retrieved:
The countersinking had taken up most of the hour that I had to spend in the shop, and I hadn't even gotten to the part where I needed to use the Uni-bit! I didn't figure that part would take too long, though. I don't like using the Uni-bit for precisely the reason that I thought the job would go quickly: they make a big hole very quickly. It actually takes quite a bit (heh) of caution to avoid going a step too far and making the hole too big. The big hole on the left would have to be finished by removing the small amount of metal at the bottom of the hole. That would be done with cutters and files.
Starting with the big hole:
Even though the larger bit on the right has a 7/16" step, I thought it would be safer to use the more tapered bit on the left for the 7/16" holes because it would give me a wider step between holes, hopefully providing the buffer I'd need to keep from over-drilling the holes. The big bit worked fine on the 3/4" hole since that was the maximum diameter of the bit anyway.
I put the filing off for last. The plans suggested a round file for that. I ought to look into getting one. I just used my little jeweler's files - that took awhile!
I finished it up just as my hour expired.
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