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Countersinking for Z Bracket on Spar

Flying C

Flying C

Member
Ok..this maybe a very obvious answer to this question, but I sure can't seen to find it. I am getting ready to countersink the spar in order to attached the K1000-3 platenut to the aft side of the spar. This is an attachment point of one of the Z brackets. My question is, how do you get your countersink tool into place? The cage on my countersink tool is a little too wide so I can't get the countersink bit into place for the two outside holes. See attached picture.
I have looked on Avery's website to see if there was a special countersink tool, but I didn't see one. How has everyone else been doing this?
Thanks,
Jake
 
Take the cage, spring, and jam nut off and countersink freehand without them. It's a skill you will occasionally need throughout the build.

John Siebold
 
John beat me to it.
I would just add; practice on scrap first.
It takes a knack, but it's easily learned with practice.
 
Better yet, just buy a bunch of NAS "platenut" rivets from Van's. They have a super small head that requires only a few turns of your deburring tool to get the required countersink. If I ever built again, that's the one thing I'd do different... attach all platenuts that way. I didn't learn about them until halfway through the build. No problems in tight spaces and no need to dimple for platenuts either.
 
I agree with what Steve said. Get some NAS 1097 "oops" rivets and use them throughout the project for platenuts. They're not structural, since all they do is hold the platenut in place. I use my deburring bit freehand in my slow battery-powered drill to countersink slightly for these rivets. Works great!
 
You'd still need to countersink for the pop rivets so the brackets can lay flat on the spar web.

On my -10, if there is a step to countersink the F-1004K parts for the side skin dimples (it is a doubler around the spars where the aft and mid skins join), I never saw it. So it was in place with a lot of holes to countersink. I had to hand countersink a couple near the top of the spar. For the rest, the cage would fit but not the drill motor so I had to cut down an old conduit-cutter extension to about 12". Then I discovered the flush rivets in the deck pieces (door cutouts where the canopy shell rests) near the corners could not be reached except by hand. I also hand countersink the fiberglass parts as they are flexible enough to be inconsistent using a cage,
 
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