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What’s the difference between coarse vs. fine thread drywall screws? Can either be used to screw down TG subfloor? If so what size? Thanks.
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neither, get yourself some deck screws.
*All you wan't to know about screws: http://www.mcfeelys.com
*Lumberyards around here have cheap screws with brittle shanks, and heavier screws that are specifically made for screwing down subfloor. Rich's suggestion about McFeely's is also good. Outstanding screws, but expensive.
*Maybe expensive but if deck screws are not used and SHEETROCK screws (notice that the name indicates something about their designed use - just like SNOW tires does, or DECAFFIENATED coffee, or LARGE PRINT edition) get substituted at least a third of the shanks will be busted at insertion and probably another twenty percent will be snapped within six months of traffic. That means you would need to use at least twice as many screws plus the labor to zip them in to have a marginally acceptable fastenning. So how cheap are the SR screws now?Using SR screws would be like buying used, half bald tires for your car before traveling across the country because you can buy them for less.I remember attending a safety certification course which was topped off with a slide show (entertaining if you have a morbid sense of humour) of sites inspected in the aftermath of accidents. I can still visualize one and hear all the laughter erupting as the instructor announced a new slide with, "This one was caused by a carpenter who thought that 20- three inch SR screws would be enough to build this staging for three men to work two stories up in the air. Does anybody here believe that SR screws are structural?"
*Amen to all above! However, fine thread sheetrock screws work well when you put sheetrock up on metal studs or into the plastic ribs on CIF's. Coarse are used for wood.
*Frenchy,that reminds me; re: metal studs, do you use fine thread regular drywall or prefer the self tapping screw when hanging 'rock? The reason I ask is sometimes suppliers in my area don't have in stock the self tapping so I wonder if there is a faster way to drive regular fine thread without waitng to long for the screw to work its way into the metal stud.A couple of years ago I decided to drastically reduce my inventory of materials. So that's out.
*Frenchy got it...coarse thread for wood, fine for metal, structural screws for structural applications.
*Rich,They are actually self-drilling and are typically used on 20 gauge studs and heavier. Most of our guys will prefer to use fine thread screws on both the 20 gauge and the 25 gauge studs rather than carry two screws. When screwing to the 20 gauge, we just push harder.
*but if it doesn't catch quickly, while the screw is sitting up trying to punch through it is wiggling a larger hole in the sheetrock with powder falling out. You can end up with a hole too large and so the screw isn't holding as well as it could.
*Well, like they say a little knowledge can be a dangerous thing. So if drywall screws are out, what should I ask for- wood screws? deck screws?- are these the same type of screws used for exterior decks or is that something different? Thanks to all those who have helped so far.
*Piffin, That's not quite as bad as you'd think. Let me try to explain, In a perfect world you wouldn't want any thread in the sheet rock and just thread in the stud. When a hole is ground in the sheet rock, you're just predrilling the hole for the sheetrock. The reason you don't want thread in the "captured" material is because that can then hold the captured material away from the clamped material. (hmm that was plain as mud....) OK try this, get a 2" screw and drill it all the way thru a 2x4 untill about three threads show, now put it down on to another piece of wood and continue to screw. The only way the two pieces will be calmped tight together is if somehow you can manage to strip the screw loose in the 2x4. Now predrill a hole just slightly larger than the screw in the 2x4 and again put the screw thru the hole exposing three threads again and now tighten. You will have the same holding power as when you screwed into the 2x4 and everything will be tightly clamped. I guess what I'm trying to say is the hole in the clamped material doesn't matter, just the threads into the material being clamped.
*Myles, You need the screws designed for subfloor decking. They have a 3/4 inch smooth shank at the top. Read my post to Piffin to understand why. If you can't find them, you really should predrill,, yeh, I know, but hopefully this is your house and you won't mind the extra work if the job is done right. You just predrill thru the sub floor and not into the stud. Just for information, I see less than 1 in 5 contractors use the correct screw in this aplication, including some that are building multimillion dollar homes. Since I have limp wrists (OK go ahead and laugh....) i like to use squre drive screws in this aplication since they seem to cam out less than the phillips head versions. That means I can screw more screws before I start to strip them out and have to replace the bit.
*myles,Ask for DECK SCREWS. And use a MINIMUM of #7, but preferably #8 size (refers to diameter). El cheapo screws will be #6 or smaller. Don't use these.Usually, 1 5/8" and shorter will be #7, and 2" and 2 1/2" will be #8. You won't need anything longer than that for subfloor or underlayment use. James DuHamel
*What are thoughts on drywall screws for holding up kitchen cabinets? I have seen a 36" wide x 42" high wall cabinet attached only with 4 screws and no grommets. Cabinet was full of grandmas antique dishes. Not a chance I'm willing to take!
*James, got to put in my 2 cents on sizes. I think most of the 1-1/4 & 1-5/8 screws at HD are #6, certainly way too small for decking.Geoff, it scares me every time I look in our upper cabinets, and see what the wife is hanging off a few 2" screws. I wonder why they have held this long.
*Pif,exactly!
*myles -I'd say go to a lumberyard (Not Lowes or HD),tell them what you're doing, and ask for their recommendations. If what they offer seems wimpy, ask if they have anything heavier. Galvanized screws are probably a good idea. Even though they will be inside, they may get some rain before the building is closed in. Helps keep the subfloor looking good.There's a good example of what Frenchy was trying to explain here: http://store.yahoo.com/squaredrive/fasteners-screws-flat-head-unplated-square-drive-optimized-thread-auger-point.html
*Ed,i I think most of the 1-1/4 & 1-5/8 screws at HD are #6, certainly way too small for decking. That is exactly why you need to avoid those particular screws. The 1 5/8" screws I buy are #7, and are tough little buggers. The 2" and 2 1/2" I buy are #8. Deck screws are much tougher, and are made to handle a lot more torque, providing you buy good qulaity DECK screws, and not the el cheapo galvanized equivelent of a drywall screw. The deck screws I buy have a coating that is colored. The screw itself is rust proof, streak proof, and strong as heck.James DuHamel
*I use GRK from canada for most structural work.Same for cabinets. In doing demo, I've taken out lots of cabs. Quite a few have been installed with SR screws. (I probably even did a few myself before I knew any better) I'd ssay that at least 25% of the screws holding cabs had been fractured and were not holding. I've seen a whole run , beginning to sag of course, still held up with only three screws still solid.Does anybody know how to spell liability?
*Hi guys, I agree with mongo and frenchy, I learned that nails bend, but drywall (multipurpose) screws improperly used, can break.I have even heard of some guys who wont use a drywall type screw to hang wall cabinets. Hardened screws are so hard they snap. I guess a deck screw might be stronger. Is there a special screw for hanging cabinets? Something with a high shear strength?C
*Me again guys,By the time I had posted my last message you all had answered my questions on hanging cabinets, "use a structural screw."Thanks.C
*we understand----web delay
*PiffinI appreciate the understanding.c
*Is a deck screw necessarily a structural screw? How about "all purpose" screws?
*cabinet installation screws
*these are my all purpose screws- a 1 1/4" screw will solidly fasten together 2 chunks of 3/4 solid maple, self countersinking, without predrilling or splitting
*Sh*t......I didn't know that about Donald Duck !
*I'll bet Ron T knew.
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What's the difference between coarse vs. fine thread drywall screws? Can either be used to screw down TG subfloor? If so what size? Thanks.