Vent screw keeps falling out

I have one screw that will stay in the ceiling metal register for a few months at a time, but it always falls out.
How can I repair this so it has something to 'grab'? I have wrapped Teflon tape around the ridges of the screw to hopefully give it more surface area to attach to...
thanks!
JohnH
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Very often it's possible to tap threads, and use the next sizer larger screw.
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Christopher A. Young
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wrote:

Take the register down and look at the sheet metal flange... it probably has no support behind it other than drywall and the sheet metal is tripped out. You can probably find a Tinnerman nut at the hardware store that will slip over the flange edge and give you something to "screw to".
...Jim Thompson
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If the screw is going into wood, without the metal register in place, put some glue on toothpicks and stuff in the screw hole in the wood breaking off the toothpicks flush with the surface. Put the metal register in place and put the screw back in.
If the screw is going into metal, get the next greater size and put some Lock Tight on the screw before using it to attach the register being sure not to over tighten.

Teflon
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Teflon
This is Turtle.
The best way to stop this is to get you a #8 Hex head sheetmetal self-drilling Screw 2.5 inches long and put two new screw in the register and be done with it. The problem is your not reaching the sheetmetal box that it is attached to above the register with the regular screws supplied by the register manufactor. The extra 1.25 inches will reach the sheetmetal box and go into it and it will not come out again. If you reach the sheetmetal box and go into it you will find that the drill point on the sheetmetal screw will come in handy for these screws are made to pop right through the sheetmetal box and hold it real good.
Now the screw described above it sold at any Nuts & Bolt supply houses, Refrigeration Supply houses, Any small appliance parts supply houses, and any hvac or heating service company that is in the phone book. If you call any hvac or furnace contractor and ask for 2 regular 1/4" hex head sheet metal screws 2.5 inches long and they will probley give them to you if you would just come get them. They cost about 4 cents a piece and as me being a hvac contractor would give you two of them to just get me in your thoughts in case you have any hvac trouble in the future. You asking for something like this is the best advertisement there is in getting new customers. Now if they only have the 2 inch ones use them for they will work fine too. i say only the 2.5 inch ones is you really go a good ways in the reciever box to hold extra good.
Now you really need to put the screws in with a drill and a nut driver chuck to make it spend fast to drill the sheetmetal box to start the hole. You can do it with a screw driver but it will take a minute to do it that away.
Now if you can't find them in your area. E-mail me and give me your snail mail address and i will tap two of them to a piece of paper and send them to you.
TURTLE
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You could certainly undertake a detailed and highly mechanical approach as describd by Turtle, which I'm guessing will indeed work. But going low-tech first seems to work for a lot of people, especially if the screw is only holding the register cover in place, like to the drywall, and not actually holding up something important, like duct work, in place. Personally, I'd first try jamming a wooden matchstick or a tiny bundle of toothpicks into the screw hole and then trim off the excess matchstick or toothpicks so they're not sticking out of the screw hole. Then I'd drive in a proper-diameter sheet metal screw into the hole that I've filled with cheap-ass household wood product.
But that's just me, and maybe not even recommended by actual home improvement professionals.
AJS

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This is Turtle.
I'm one of them damn old do it right the first time types. Just a habit.
TURTLE
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tuta wrote:

I saw the solution to this in the movie "Murder at 1600". You have to go upstairs, find the federal agent who is bugging your house with a vent cam, and shoot him. Let us know how this works out.
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