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Nutplates...do you re-tap them?

RandyAB

Well Known Member
I'm finding that the nutplates that I have been installing are incredibly tight when I try to insert the hardware meant for that nutplate. I actually snapped a screw on the access panels for the trim on the elevators. I ended up having to run a tap through each of them so I wouldn't have to torque so hard. Yesterday I inserted the bearings into the larger nutplates for for the elevator and rudder and boy were they tight as well. The hardware that I used is correct and I used Beolube.

I was wondering if builders regularly re-tap the nutplates before installing them?
 
tap

Yes, but don't run the tap all the way in, just a couple of turns so you only loosen it up just a bit, but it it will still hold torque, Some plates in non critical areas when the screws don't play a structural role, such as an interior panel may be tapped deeper.
 
Generally tapping at all is a bad idea, but I have gotten some off branded ones that had over crimped lower ends and were extremely tight. There are some nut plates that have a coating just for this reason.

I always use liquid boelube but have resorted to a tap for a few turns for some 4-40 screws. (shame on me)

Oh - always use steel screws to break in the new ones, not stainless screws.
 
Using Torx screw rather then Phillips will solve the problem immediately. A little lube on the threads is good also. If you go with Torx be sure to buy good tools, Snap On or Mac are the best domestic but the Dewalt driver bits available at Home Depot are just as good and much cheaper. They are also good for Phillips bits.

Another big problem is not using the right size bit or screwdriver. You need the exact Torx bit ( 15,20, or 25) and either a #1,2 or 3 Phillips. The wrong bit (end) will strip out the head real fast, especially in the SS screws the aviation industry likes.
 
No - using Boelube should be adequate.

Carl

If you do not have Boelube, Bee's Wax or even candle wax work well. I have a block of Bee's Wax purchased at a 'Gun Show' that is what I first reach for. May have something to do is that what we used at work over 30-years ago.
 
Using Torx screw rather then Phillips will solve the problem immediately. A little lube on the threads is good also. If you go with Torx be sure to buy good tools, Snap On or Mac are the best domestic but the Dewalt driver bits available at Home Depot are just as good and much cheaper. They are also good for Phillips bits.

Another big problem is not using the right size bit or screwdriver. You need the exact Torx bit ( 15,20, or 25) and either a #1,2 or 3 Phillips. The wrong bit (end) will strip out the head real fast, especially in the SS screws the aviation industry likes.

The head didn't strip, the bolt sheared right off!

In Canada we have Robertson square heads that are much better than Phillips heads. I don't know if they are used south of the border at all.
 
If you do not have Boelube, Bee's Wax or even candle wax work well. I have a block of Bee's Wax purchased at a 'Gun Show' that is what I first reach for. May have something to do is that what we used at work over 30-years ago.

Good to know!
 
Tap

Yes, but don't run the tap all the way in, just a couple of turns so you only loosen it up just a bit, but it it will still hold torque, Some plates in non critical areas when the screws don't play a structural role, such as an interior panel may be tapped deeper.

I do it this way too. Boelube on the tap.
 
I tap nutplates for interior panels. In the 10 years my RV-6A has been flying, the seat pans and even the baggage bulkhead have never fallen out. I also replaced screws with allen head screws. You can get allen pan head screws for areas under the carpet and seats.

For the exterior screws (tank attachment especially) I don't use a tap but I will run a stainless steel, allen head screw through the nutplate before I run a regular screw in there, to allow for the over-crimped plates because I have ruined too many screws. I also keep a healthy oversupply of screws because even now every once in a while, one will strip the head.
 
I'm with Patrick. I use Allen head cap-screws when I can, they are usually black phosphate coated, which is a lubricant in itself.
I like to use a dab anti-seize compound on the tip of the threads of the first screw into a new nut-plate. It's a little messier than Boelube or wax, but I think it does better job.
 
I think you guys have convinced me that I need to just bit the bullet and buy some allen head or torx screws for my wings.

Is there a good part number cross reference out there somewhere that will let me find the right screws (hardness, size, flush head degrees, etc)? It'd be nice to be able to swap out all of them with either torx or allen head, even the countersunk ones.

I'm guessing McMaster Carr is probably the cheapest place to buy them? Any other good recommendations?
 
To good to be true, maybe, but it's cheap to try it . .

I think you guys have convinced me that I need to just bit the bullet and buy some allen head or torx screws for my wings.

Is there a good part number cross reference out there somewhere that will let me find the right screws (hardness, size, flush head degrees, etc)? It'd be nice to be able to swap out all of them with either torx or allen head, even the countersunk ones.

I'm guessing McMaster Carr is probably the cheapest place to buy them? Any other good recommendations?

Deja vu all over again. Every few years this topic comes up, it starts with nut plates, breaking screws, then stripping, then using stainless (worse BTW) then using allen or torx heads, then some esoteric company that will sell a 100 deg head.

Well - I got pulled into this same discussion early in my build and kept it in mind for many years. Here is what I accidentally discovered -driver bits - if you use these with a phillips screw (carbon steel/cad screws) it is very strong, less likely to slip and you can take a little longer screw (or a hand full of them) and use with an electric nut nut driver to rapidly spin the screw in and out of a green nut plate. Antiseize selection is your choice, use what works, but you can get really happy with phillips screws. And if you need another hundred, they are very easy to source from Spruce or other suppliers. Like anything, a good brand is important, but you can pitch a lot of $0.40 Wiha #2 phillips bit for the price one $8 Wiha screw driver.

Don't knock the phillips for slipping until you try some good driver bits, even ACR bits. I found they are 10x better than a typical screwdriver. Cheap and easily replaced, work very well. Better, faster, AND cheaper. Almost like a miracle.

OK - so they are not good for tight spaces, but a Wiha, SnapOn or other pricey hand tool will work in those rare places. But for glass tips, floor panels and the like, the driver bits (maybe a good ACR) should be on your list to try. The cheap, poorly made, evil screw drivers (Craftsman) have ruined the good rep of phillips head screws.

Stainless screws do look good, so I used them after the panels, tips etc have been on and off a dozen times and ready for final assembly. Then replace them all with new stainless after everything is broken in and using new driver bits.

Just something to try.
 
Deja vu all over again. Every few years this topic comes up, it starts with nut plates, breaking screws, then stripping, then using stainless (worse BTW) then using allen or torx heads, then some esoteric company that will sell a 100 deg head.

Well - I got pulled into this same discussion early in my build and kept it in mind for many years. Here is what I accidentally discovered -driver bits - if you use these with a phillips screw (carbon steel/cad screws) it is very strong, less likely to slip and you can take a little longer screw (or a hand full of them) and use with an electric nut nut driver to rapidly spin the screw in and out of a green nut plate. Antiseize selection is your choice, use what works, but you can get really happy with phillips screws. And if you need another hundred, they are very easy to source from Spruce or other suppliers. Like anything, a good brand is important, but you can pitch a lot of $0.40 Wiha #2 phillips bit for the price one $8 Wiha screw driver.

Don't knock the phillips for slipping until you try some good driver bits, even ACR bits. I found they are 10x better than a typical screwdriver. Cheap and easily replaced, work very well. Better, faster, AND cheaper. Almost like a miracle.

OK - so they are not good for tight spaces, but a Wiha, SnapOn or other pricey hand tool will work in those rare places. But for glass tips, floor panels and the like, the driver bits (maybe a good ACR) should be on your list to try. The cheap, poorly made, evil screw drivers (Craftsman) have ruined the good rep of phillips head screws.

Stainless screws do look good, so I used them after the panels, tips etc have been on and off a dozen times and ready for final assembly. Then replace them all with new stainless after everything is broken in and using new driver bits.

Just something to try.

I need to quit assuming. I thought everyone used ACR screw driver bits. The lube helps but you must have the correct tool to do the job.

853-1-tz-acr-bit.jpg
 
If the screws are snapping when using boelube or equivalent, the drivers don't matter. In this case, Torx head will not help, and will be weaker in torsion.

I had a batch of -8 nutplates from Van's a couple decades ago that were the same way. I fixed them by using a vise-grip on the body, in the opposite direction as the factory crimp. It took some trial and error to get the vise grip set, to be sure that a fair bit of residual factory crimp was present. Easier than tapping post install, but obviously needs to be done prior to install.
 
I had same experience until I started using Johnson's paste wax to lube threads prior to install. Made them MUCH easier to install. No problems since.

I would assume Boelube would do the same, but haven't personally used any, so not sure if paste wax is better or not.
 
A bit of Phillips History? (pun intended)

Early in my engineering career I was told by a wisened old dude that Phillips screws were explicitly designed to "torque out", i.e. have a slipping point to limit the amount of torque that could be applied . They were a solution to overtorquing and stripping problems that were rampant in assembly plants factories in that day. We neophyte engineers were told, "if you want something that gobs of torque can be applied to, don't use Phillips!" Ever since, I don't hesitate to replace Phillips with allen head, torqx, or square drive whenever applied torque - or access - are a problem.
..... so the next time your muttering about a stupid, slipping Phillips head screw, recall that it's just performing as designed. :)
 
I have found that the best lube for screws and hinge pins is the wax of a toilet bowl ring. This is a soft beeswax. The only places I have had to ream nut plates was the lowest screw on wheel pants and the floor panels closest to the fuselage. Never had any come loose.
 
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Tapped all my #6 and #8

Made a little jig, used Boelube or candle wax. One pass with a well lubed tap and done. Never had any problems.
 
WRT the OPs original question, I tap all my nut plates with a regular tap.

For the ones that worry me (ie keep me awake late at night) they either get a dab of Locktite242 OR the nutplate gets slightly re-squeezed to bring back that bite. And a new screw.

In my build, I have a lot of nutplates, over a 1000 easy - folding wings, associated panels and structure that needs to be removable for mx will do that. I'm taking most of these screws in and out 10s of times, some close to a 100times in the build phase alone. To have them bite while I'm being creative is a pita.
 
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