Drilling Nut Plates
 

I have had a problem getting nut plates centered properly. My usual technique has been to drill the center hole, then cleco the nut plate in the appropriate orientation and drill through the two rivet holes. I have ended up with the nut plate off center by the tiniest amount, maybe the width of the threads. It is enough to cause a lot of problems inserting the screws without stripping them.

The short term solution has been careful filing to enlarge the center hole in the skin/bracket/inspection plate.

Is there a better way of drilling these holes to guarantee a better alignment?

I may order a jig to drill them but does this solve the problem?

Thanks

Mark Jackson (RV-8 working on wings)

Instead of using a cleco, use a screw/bolt. It will not have the play that a cleco will have. Its a little more time consuming, but it will be centered.

I use a screw to hold the nutplate. Then drill one hole, cleco, then drill the other hole.

I put several washers on the #8 screw so I have just enough threads to engage the nutplate.

Nut plate jig
 

Mark, I would recommend a nut plate jig. It will make the installation of the nut plates go so much easier and faster. Just my 2 cents worth, but I know it has saved me a bunch of time.

The nutplate jig was my FAVORITE tool from the entire build. Made every nutplate installation easy, fast, and perfect. Hint, a #6 nutplate jig will work for #6, #8, and #10 nutplates. They are not a lot of money, either.

2nd the nutplate drill jigs especially if you make the floor panels removable. After doing all the nutplates on the floors, I moved the drill jig from nice-to-have to must-have. The screw method is just as accurate but slow.

I have used three different methods.
Drill the hole to #30 so the cleco is centered for the rivet drilling. Then drill the hole to the proper size.
Or us a tap to start the threads before screwing up a screw.
Or use a screw as mentioned instead of a cleco.

Also, after the rivet holes are drilled, drill out the "screw" hole larger than normal.
Once the nut plate is installed, that center hole does nothing.

Nut Plates
 

I ordered a jig for $20 but until then will use the screws to hold the nut plates in place.

Mel,
I agree that in a lot of locations it would be acceptable to not have the hole in the structure baring on the fastener, but this is not universality the case.

A common example would be in cases were a bolt is threading into a nutplate. The use of a bolt is a strong indicator that it is a load baring fastener, so it should be in a close fitting hole.
I can think of other instances using plain screws where I would not feel good about there not being a close fitting hole for the screw.

I am currently drilling all the ribs for the seat pans and the luggage compartment - doing it with the fuselage in the jig - upside down ... and the jig is a great tool. I like the jig with the flexible arm. Not sure how long the hole in the jig will last (the jig has no bushing - I have seen one type that does - but it did not have a flexible handle) so far the hole feel tight - the steel is obviously harden - Looks like it is a US made tool so happy with the steel used in the tool. I have also done the screw in hole thing .. that works but take a lot longer ...

Home-made jig
 

I made a jig. Take a nutplate and the appropriate screw. Screw the screw into the nutplate backwards so that the threads stick out the base of the nutplate. Then use that protruding screw to align the nutplate and drill the attach holes (using a cleco after the first hole).

I wish my cheap a?? Would have bought the jig. I did so many as other said, drill, insert screw, drill and cleco, drill the other.....

nutplate
 

I have several drill jigs but wore out the #6 that I use the most and don't have a #8. I cut an assortmet of screws that are just long enough to engage the plate nut but not engage the locking portion. I drill, countersink and rivet with the temporary screw in place, sometimes several at once.

If you're talking about an area with both screw & rivet holes pre-punched, I found that simply dimpling the rivet holes in both the skin and the nut plate results in perfect alignment, & no issues with over-countersinking of the skin. Dimpling the nutplate is easy; it just takes a small diameter female dimple die or grinding off one side slightly.

I used the same technique on 'raw' sheet stock, too. I've got a nut plate with the thread locking mechanism disabled (run a tap through it several times) that I use for a drill jig, then follow up with the dimpling technique to keep the final nut plate centered under the screw hole.

Charlie