Replies

1. 
   Guest_ | Aug 26, 2000 07:16am | #1

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   b TVMDC

   Nathan, If your screws are breaking prior to seating them fully home there are a couple of things that could be happening:

   1. Using under-sized screws: if using #8 change to #10;
   2. Use auger-point self-drilling screws;
   3. Use screws that have half-threaded shanks, not 2/3 threaded as usually found;
   4. If that doesn't help, predrill the holes. You are going through 1-1/2" of flooring plus (hopefully) another 1-1/2" into the joists. If the flooring or subflooring is old or dried out, it is simply too hard for a self-drilling screw.

   By the way, I believe "torque" is the appropriate word here, not shear.

   Regards,
   Bill Pickard

1. 
   Guest_ | Aug 26, 2000 05:25pm | #2

   *I don't think ANY forged screws can be used for shear. I might be wrong, but I think you need nails or screws (like "wood screws") that start as a long wire to get any shear value.

1. 
   Guest_ | Aug 27, 2000 03:18am | #3

   *b TVMDCFYI the UBC gives NO shear values for screws in drywall even though you and I both know that screws hold better than drywall nails.

1. 
   Guest_ | Aug 28, 2000 04:39am | #4

   *Jim is right....drywall screws are not meant to hold in shear...I no longer use these for decks and docks.near the stream,aj

2. 
   John_Robb | Aug 28, 2000 05:04am | #5

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   Nathan
   I have been using the Quick drive system for about 2 years now (screw strips not the old coil system)And did have a problem with the 1 1/4 and 1 5/8 drywall screws snapping off. I have now switched to the 1 3/4 woodscrew (WSC134S) For screwing down plywood subfloors. The drywall screws are a #6 six screw and are threaded all the way to the top of the screw head,which leaves very little metal to take the stress of that lenght of screw. Case in point they snap. The wood screws are #8s which gives them more bite plus they are not threaded all the way to the top of the screw.

3. 
   Guest_ | Sep 08, 2000 03:11am | #6

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   Drywall screws are brittle. They're only for hanging drywall and other such light duty applications. If you need any strength at all, use deck screws or wood screws.

   -- J.S.

1. 
   Guest_ | Sep 08, 2000 04:26pm | #7

   *I am now building top to bottom with production deck screws: # 7's, 8's and 10's. These are a treated exterior grade, wood screw (greens, browns and golds). They have great shear strength. In driving over 10,000 screws into all kinds of situations this past few weeks, I have not had one break, no heads have turned off and many have been withdrawn and re-driven several times. For example, I use # 10 - 3.5" long - for temporary cross bracing that have been reused 8 or 10 times as we change the postiion and reposition the braces.These screws have Robertson heads (square drives) so they don't cam out unless you use them over your head where you can't bear down. Even when they bend, which is rare, they don't break. I set my Bosch cordless clutch to stall at the point of resistence I need to prevent driving the screws too deeply. Drill attachments are available for production driving of these screws.My experience with drywall screws is a bad one. They cam out since they are Phillips(designed to cam out) heads and they break. They can't be removed and reused and the threads don't work well in wood. They alsways rust and ofen pop. I would use exterior/decking wood screws for drywall. They are paintable and don't rust and can be removed and reset when necessary: #7 - 1.5" or 13/4" are available from most large suppliers.I don't believe code has kept up with screw technology. I have tested the # 10 - 3.5" screws in the same application as 3.5" and 4" ardox (spiral, galvanized dipped) framing nails and the screws are much stronger in pulling power (obviously). They appear stonger in shear since I have had no separation or movement along the shear with the screws but I have with the framing nails. I am using them to make nailed up 4X beams, frame walls and install rafters.

1. 
   Guest_ | Sep 14, 2000 06:12am | #8

   *remeber the screw only plays a part in transferring shear. Tightening the screw creates compressive stress. Compressive stress gives you the other part, called friction. Fricition resists shear good.Smooth shank nails make no compressive stress. Ring shank make a little. Ardox make a little more. But no one frames with an ardox nail because they don't make them for air nailers! Christ, I have to use the maul just to pound those in.Clamps are a good example - actually NO fastener taking the load what's with that? Compression, that's what.This is another study I have been threatening to do!! As soon as I find a sponsor I'll test every type of screw or nail with every type of lumber. Until then, this baord takes up plenty of time without generating income!-Rob

4. 
   nathan_w | Sep 14, 2000 06:12am | #9

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   They seem to be easily snapped off, when one doesn't drive all the way, or I need to break off the back side. Anyone have any thoughts on the shear value of such a screw? Application is for 3/4" t&g over 1x6 t&g fir decking, that has been chopped up while bolstering the joist for remodeling. I know a floor system has important shear, as I run into floor nailing schedules that require full perimeter blocking and edge nailing (diaghram panel). This is not the case here...

   thanks for any input