Decks, Patios, Porches and Docks - Stainless Screws shearing when driven
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luckyj
04-23-09, 01:08 AM
I've been having issues with #10 x 3 inch SS screws (305 grade, square drive #2) snapping or shearing where the smooth shaft meets the threads as the screw is driven. They are being used to attach 5/4 Trex to pressure treated joists.
It is occuring after the screw is mostly in but the head still exposed slightly above the composite. As it continues to be driven flush, it will then snap but again, not at the head but at the smooth shaft/thread merge down inside the decking. I'm able to pry them out and what comes out is the approx 1 inch or so of the head and attached smooth shaft.
I began pre drilling the holes and also using some liquid dish soap to provide lube but some of the screws are still snapping.
I've driven with both an impact driver and a normal drill but have experienced the shearing both ways. It is occuring after the screw is mostly flush but the head still exposed slightly above the deck board. As it continues to be driven flush and into the decking, it will then snap but again, not at the head but at the smooth shaft/thread merge. I don't think I'm overdriving them as they snap before they're really sunk down into the composite.
I am already using a 9/64" bit....I've also used a 5/32 bit with the same issues. Any larger will be too big.
Has anyone experienced this or can anyone suggest what I can do to avoid this??
It is occuring after the screw is mostly in but the head still exposed slightly above the composite. As it continues to be driven flush, it will then snap but again, not at the head but at the smooth shaft/thread merge down inside the decking. I'm able to pry them out and what comes out is the approx 1 inch or so of the head and attached smooth shaft.
I began pre drilling the holes and also using some liquid dish soap to provide lube but some of the screws are still snapping.
I've driven with both an impact driver and a normal drill but have experienced the shearing both ways. It is occuring after the screw is mostly flush but the head still exposed slightly above the deck board. As it continues to be driven flush and into the decking, it will then snap but again, not at the head but at the smooth shaft/thread merge. I don't think I'm overdriving them as they snap before they're really sunk down into the composite.
I am already using a 9/64" bit....I've also used a 5/32 bit with the same issues. Any larger will be too big.
Has anyone experienced this or can anyone suggest what I can do to avoid this??
chandler
04-23-09, 05:00 AM
Generally the stainless screws available are shaft-weak, and will strip the heads very easily. IMO, the anti mushrooming head screws (#2 square) made for trex in coordinating colors provide the best driving and holding ability. They will blend with your deck whereas stainless won't. Constant down pressure is essential, as well as straight line pressure.
luckyj
04-23-09, 12:27 PM
I should have also mentioned that I am able to "bury" a large portion of some screws...that is drive the heads about 1/4" into the Trex and hammer down the excess leaving a nearly invisible hole.
I just don't get why it's so variable and some screws refuse to go in without snapping....Don't know it's a screw quality issue or an issue with the older PT joists (this is a renovation just replacing the deck boards...the PT is older CCA about 10 yrs old)
I just don't get why it's so variable and some screws refuse to go in without snapping....Don't know it's a screw quality issue or an issue with the older PT joists (this is a renovation just replacing the deck boards...the PT is older CCA about 10 yrs old)