Derate screws after removing once?

[JHZR2]

I noticed on a box of tapcons that they may be reusable, but that the clamping force would be reduced once reused.

Is this the case for wood screws in wood as well? If so, what is an appropriate derating? Does the fact that a hole was/was not pre drilled make a difference? As I understand it, holes not properly pre drilled can have micro cracks around the fasteners.

Thanks!

 

[Merkava_4]

I've done some experimenting and I've found for dry 2x4s, a #40 drill bit for a pilot hole before driving in a #9 wood screw works real well. Before that I kept splitting the boards. As far as derating goes, I've never heard of that; I use my screws over and over.

JHZR2, get'ya some GRK R4s. Those screws are great. You'll never want to use ordinary wood screws ever again.

 

[IndyIan]

I suppose if you took apart your deck on a monthly basis, you might need to worry about derating the tension a wood screw could hold, but normally its not an issue.
I only predrill to avoid splitting as well, as with softwoods, usually the screw head will pull through before the threads slip, or the screw will break. In hardwoods the screw itself is the weak link.

 

[JHZR2]

All I'm going off of to spur the question is this:

"Tapcon® Concrete Screws: Tapcons are removable because they are threaded screws that taps threads into the concrete, brick or block. By simply turning the screw counterclock wise, these concrete screws will thread its way out of the base material. The holding values of Tapcons will be deteriorated if they are reinserted into the same hole."

And that's for masonry, which has different give and crumble characteristics than wood, obviously. But I'd expect that a wood hole would also be slightly damaged, slightly enlarged, etc., and so it's force would also have some compromise.

 

[bepperb]

It's not really clear from the TapCon quote if it's the screw that's derated, or the hole?

But over time a wood screw hole that's used often will definitely derate. Door hardware screw holes seem to be the worst offenders. And for some things like the strike plate holes there's really no load that could be stripping them, just the screws themselves, and yet they seem to get loose fairly early on.

I don't use screws for the very limited framing I do, but those "HZR2, get'ya some GRK R4s" look like the real deal.

 

[kschachn]

I use a lot of Tapcon fasteners, and I'd have to say that it is strictly the hole (or rather the material). It depends a lot on the material and the care that is used to drill the hole, a sloppy and oversize hole in relatively soft brick will be much less effective than a clean hole in solid concrete. I've taken Tapcon fasteners out of softer material where I could virtually push it back in by hand. Obviously that isn't going to hold much tension.

Originally Posted By: bepperb
It's not really clear from the TapCon quote if it's the screw that's derated, or the hole?

But over time a wood screw hole that's used often will definitely derate. Door hardware screw holes seem to be the worst offenders. And for some things like the strike plate holes there's really no load that could be stripping them, just the screws themselves, and yet they seem to get loose fairly early on.

I don't use screws for the very limited framing I do, but those "HZR2, get'ya some GRK R4s" look like the real deal.

 

[JHZR2]

Originally Posted By: bepperb


I don't use screws for the very limited framing I do, but those "HZR2, get'ya some GRK R4s" look like the real deal.



I have a framing nailer with big ol nails for when I need to frame anything. I'm sure screws do ok, but their brittleness makes me avoid them in preference of real nails. Perhaps a nail-screw combo would be prudent sometimes.

But screws are good for so much else. I use spax almost entirely, since they are us/German made and roughly the same price as the Taiwanese stuff in a 1lb box.

 

[spasm3]

Originally Posted By: JHZR2
I use spax almost entirely, since they are us/German made and roughly the same price as the Taiwanese stuff in a 1lb box.


I have used the Spax also, they are tough the heads seem tougher and dont ream out as easily.