Spinner Question

[FireMedic_2009]

Yes match drilling the rivet holes with the nutplate on the outside may not align perfectly when you put the nutplate on the inside, so wollow the holes towards the inside. The nutplates are not structural, the rivets don’t have to be absolutely perfect. When you squeeze the rivets it will fill most of the hole. The nutplate is only there to secure a screw. It only needs not to turn. It’s not necessary to be cosmetically perfect if you don’t see it. You can spend 6-8 hours being perfect that no one sees or 1.5 hrs and on to the next task. If you do one you’ll see that there’s not much of a difference between perfect

[Webb]

Make a jig. Then you can drill from the outside.

Take 2 scrape pieces of 0.125 and stack. Bend to the same curve. Using a plate nut for a guide on the inside of the curve, drill 2 guides.

The outside is now your template for drilling. The inside was the curve of the spinner. Using 2 dull drill bits, a #40 and the size needed for the screw. Break off a short piece and grind the end smooth. Reason for 2 guides is the curve.

Flush rivet the piece that was the inside curve on top and then drill it using the inside piece as a guide. Make sure you are making new holes in the top and it has the same curvature as the inside. I put the guides on each end of my jig. That way you just swapped ends instead flipping it over like the flat nut plate jigs.

JB Weld the drill bit stubs in the holes with a 1/8” sticking out. Curve 1 gets just a center stub. Curve 2 gets a center stub and an alignment stub.

It took me longer to type this than to make the jig.

You are making one of these but have to make 2 guides because of the curve.

[rvbuilder2002]

Originally Posted by Webb

Make a jig. Then you can drill from the outside.

Take 2 scrape pieces of 0.125 and stack. Bend to the same curve. Using a plate nut for a guide on the inside of the curve, drill 2 guides.

The outside is now your template for drilling. The inside was the curve of the spinner. Using 2 dull drill bits, a #40 and the size needed for the screw. Break off a short piece and grind the end smooth. Reason for 2 guides is the curve.

Flush rivet the piece that was the inside curve on top and then drill it using the inside piece as a guide. Make sure you are making new holes in the top and it has the same curvature as the inside. I put the guides on each end of my jig. That way you just swapped ends instead flipping it over like the flat nut plate jigs.

JB Weld the drill bit stubs in the holes with a 1/8” sticking out. Curve 1 gets just a center stub. Curve 2 gets a center stub and an alignment stub.

It took me longer to type this than to make the jig.

You are making one of these but have to make 2 guides because of the curve.

My experience is that there is usually enough play in the guide bushing of a drill guide for the drill bit, that drilling on the curved flange through the rather thick material of the bulkhead can still result in rivet hole spacing that doesn't match the nut plate.
Sure, you can wallow out the rivet hole to get it to work as has been suggested, but then in some cases the nutplate then ends up not being centered on the screw hole. So then you wallow out the screw hole to make that work.
Then after a few years of flying you are frustrated that screw holes are smoking and nutplates are loose on your spinner (hardware on a spinner lives a much harder life than it does on most other parts of the airplane).
There are often very specific reasons that the plans specify doing something a certain way....

[asw20c]

To closeout this thread I thought I would offer how I resolved this issue.
Early on in my project I decided to buy a mill and a lathe because every now and then I needed a tool for a specialized application and either didn't want to wait for it to arrive, or the tool didn't exist, so I'd make one. This time, working with a buddy of mine who has a 3D printer, we worked together to make a tool that would allow drilling from outside the flange rather than inside. We took careful measurements of the rear bulkhead diameter and adjusted for the centerline of the flange. We could accurately measure the thickness and the dimensions of the nutplate, and also accounted for the cone (the surface is curved in two directions) and ended up making a guide that clamped to the flange and was located by the screw hole. I made steel drill bushings on the lathe that I pressed into the drill clamp, and if I were to drill any more holes than were required, would have made them out of hardened tool steel, but for this experiment just used plain mild steel.
It worked beautifully! After drilling the #40 rivet holes from outside the flange using this homemade drill guide, the rivets lined up with the nutplate rivet holes on the inside of the flange without having to use a pick or having to "walk" a hole. We thought we might have to tweak some of the dimensions, but apparently we nailed it on the first try. I love it when a tool works as intended!