Tip: Close tolerance nut plates

My RV-8 front baggage area has lots of nut plates to hold the panels in. A friend's RV-8 had several stuck, or broken, number 8 screws in tight areas of this compartment. There is a elegant solution to this problem. Measure the drive area on the end of an 8-32 tap. Select a STEEL nut with a somewhat smaller thread pattern then this head and drill the threaded area out. Use a drill .004 or .005 inches smaller than the widest part of the drive head on the tap. Securely clamp the shaft of the tap in a vise, above the cutting threads, and gently hammer the modified nut onto the end of the tap. You now have a tool that will fit very close to the skin of the aircraft. Using a small ratchet and appropriate socket, run the tap into the nut plates to gently remove some of the locking action of the nut plate. Take it slow and be careful not to go too deep. A deep well socket seems to produce less side load on the fragile tap, and acts like a universal joint in operation.

Nutplates

Good idea.

Nutplates are so inconsistent. Exactly why I spend the extra time to check every one. I've found some with no tension and others so tight it damages the screw. For the floors, I run a tap in three turns. It leaves a nice snug fit. For other areas, I run a screw in and back out. If it's so tight the screw gets galled, I run a tap in a couple turns and check again. Boelube on the tap and screws as well.

Another approach - burnishing

Get some socket head cap screws of the desired size at Ace Hardware (they are very hard), and an appropriately sized hex bit that can be mounted in your electric screwdriver or drill. Clamp the nutplate into the vise by its ear, put some Boelube on the capscrew, and run it in and back out with the electric tool, repeat as necessary. I generally do them in batches so they are always ready for installation, but they can easily be done in place as well. I have a ziplock bag in the tool chest with capscrews and bits for 6-31, 8-32, and 10-32. This process smooths out the rather rough phospated finish without actually removing any metal. Of course if you find any that are way too tight or too loose for your taste, you can pitch them at this time. Plenty of retention capability and no galling issues.

Another good method

William Slaughter: That is a great suggestion, too, as long as you have room to work. I always prep the nut plates before installation. Here I was faced with a bunch of nut plates installed by a previous builder that did not prep before install. Naturally, these dozen nut plates were too close to the skin to get to them easily.

William Slaughter said:

Get some socket head cap screws of the desired size at Ace Hardware (they are very hard), and an appropriately sized hex bit that can be mounted in your electric screwdriver or drill. Clamp the nutplate into the vise by its ear, put some Boelube on the capscrew, and run it in and back out with the electric tool, repeat as necessary. I generally do them in batches so they are always ready for installation, but they can easily be done in place as well. I have a ziplock bag in the tool chest with capscrews and bits for 6-31, 8-32, and 10-32. This process smooths out the rather rough phospated finish without actually removing any metal. Of course if you find any that are way too tight or too loose for your taste, you can pitch them at this time. Plenty of retention capability and no galling issues.

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+1 - I Like - I do this too

Way too much trouble ....

You guys are making it way too hard .... get a bottle of Boelube FLUID, put a drop (or two) on the screw and just turn it in! You will be amazed at the difference it makes ........

Boelube is a machine cutting oil for drilling, cutting, etc, which is actually what the screw is doing in the nutplate as you force it through. Best $5.64 you will ever spend. Avery Tool also stocks it and maybe Spruce does as well. Do not get the solid wax form.





Just saying.....

Lubricant is nice...

but my point was that, when access sucks, making one major crawl into the structure to ease installation of screws in the future, with lubricant, makes sense. Once the structure is built you do not have leverage to easily screw things repeatedly in and out, nor room to use powered equipment. Just not enough room deep inside the baggage compartment. Best solution is to do this before the nut plates are installed, next best is a combination of all the above recommendations. YMMV

BillSchlatterer said:

You guys are making it way too hard .... get a bottle of Boelube FLUID, put a drop (or two) on the screw and just turn it in! You will be amazed at the difference it makes ........

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A bit of bees wax (from a hardware store toilet bowl seal) on each screw works well also ...

This has been one of my favorite tools:

http://www.blackanddecker.com/en-US...screwdriver-with-compactfit-technology/li3100

The drive end is offset and will fit right up against the sidewall. It's perfect for the RV-8 baggage area, almost as if it was made for us!

Jerry Esquenazi
RV-8 N84JE

wirejock said:

Good idea.

Nutplates are so inconsistent. Exactly why I spend the extra time to check every one. I've found some with no tension and others so tight it damages the screw. For the floors, I run a tap in three turns. It leaves a nice snug fit. For other areas, I run a screw in and back out. If it's so tight the screw gets galled, I run a tap in a couple turns and check again. Boelube on the tap and screws as well.

Click to expand...

If the locking action isn't critical, I often will run a tap through it completely. Often I will run a screw in and then back it out. In all my thousands of nutplates experiences, I actually found one that had no threads in it. The machine missed that one, although it's surprising that I have only seen that once.

I have run a tap thru every -3 or smaller nutplate in both my RV's except for a few critical applications. There is a lot of spring back in the nutplates and after a tap job they still exhibit a fair amount of friction. Never have found a missing screw or nut, or even a loose one. I'm convinced that if you actually tighten a screw in a nutplate, it takes almost no friction to keep it tight.

A critical application is one where there is potential movement between the parts, like a single screw anchoring a cable clamp. Something with more than one screw is never critical.

Also, when putting a bunch of screws in for the first time, I put them in a paper cup and give it a nice shot of Beolube and shake well. It seems that once lubricated, nutplates stay that way.

Now I'm running for the hills!